`
.. option:: -pedantic
Warn on language extensions.
.. option:: -pedantic-errors
Error on language extensions.
.. option:: -Wsystem-headers
Enable warnings from system headers.
.. option:: -ferror-limit=123
Stop emitting diagnostics after 123 errors have been produced. The default is
20, and the error limit can be disabled with `-ferror-limit=0`.
.. option:: -ftemplate-backtrace-limit=123
Only emit up to 123 template instantiation notes within the template
instantiation backtrace for a single warning or error. The default is 10, and
the limit can be disabled with `-ftemplate-backtrace-limit=0`.
.. _cl_diag_formatting:
Formatting of Diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^
Clang aims to produce beautiful diagnostics by default, particularly for
new users that first come to Clang. However, different people have
different preferences, and sometimes Clang is driven not by a human,
but by a program that wants consistent and easily parsable output. For
these cases, Clang provides a wide range of options to control the exact
output format of the diagnostics that it generates.
.. _opt_fshow-column:
**-f[no-]show-column**
Print column number in diagnostic.
This option, which defaults to on, controls whether or not Clang
prints the column number of a diagnostic. For example, when this is
enabled, Clang will print something like:
::
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
When this is disabled, Clang will print "test.c:28: warning..." with
no column number.
The printed column numbers count bytes from the beginning of the
line; take care if your source contains multibyte characters.
.. _opt_fshow-source-location:
**-f[no-]show-source-location**
Print source file/line/column information in diagnostic.
This option, which defaults to on, controls whether or not Clang
prints the filename, line number and column number of a diagnostic.
For example, when this is enabled, Clang will print something like:
::
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
When this is disabled, Clang will not print the "test.c:28:8: "
part.
.. _opt_fcaret-diagnostics:
**-f[no-]caret-diagnostics**
Print source line and ranges from source code in diagnostic.
This option, which defaults to on, controls whether or not Clang
prints the source line, source ranges, and caret when emitting a
diagnostic. For example, when this is enabled, Clang will print
something like:
::
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
**-f[no-]color-diagnostics**
This option, which defaults to on when a color-capable terminal is
detected, controls whether or not Clang prints diagnostics in color.
When this option is enabled, Clang will use colors to highlight
specific parts of the diagnostic, e.g.,
.. nasty hack to not lose our dignity
.. raw:: html
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
When this is disabled, Clang will just print:
::
test.c:2:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
**-fansi-escape-codes**
Controls whether ANSI escape codes are used instead of the Windows Console
API to output colored diagnostics. This option is only used on Windows and
defaults to off.
.. option:: -fdiagnostics-format=clang/msvc/vi
Changes diagnostic output format to better match IDEs and command line tools.
This option controls the output format of the filename, line number,
and column printed in diagnostic messages. The options, and their
affect on formatting a simple conversion diagnostic, follow:
**clang** (default)
::
t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int'
**msvc**
::
t.c(3,11) : warning: conversion specifies type 'char *' but the argument has type 'int'
**vi**
::
t.c +3:11: warning: conversion specifies type 'char *' but the argument has type 'int'
.. _opt_fdiagnostics-show-option:
**-f[no-]diagnostics-show-option**
Enable ``[-Woption]`` information in diagnostic line.
This option, which defaults to on, controls whether or not Clang
prints the associated :ref:`warning group `
option name when outputting a warning diagnostic. For example, in
this output:
::
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
Passing **-fno-diagnostics-show-option** will prevent Clang from
printing the [:ref:`-Wextra-tokens `] information in
the diagnostic. This information tells you the flag needed to enable
or disable the diagnostic, either from the command line or through
:ref:`#pragma GCC diagnostic `.
.. _opt_fdiagnostics-show-category:
.. option:: -fdiagnostics-show-category=none/id/name
Enable printing category information in diagnostic line.
This option, which defaults to "none", controls whether or not Clang
prints the category associated with a diagnostic when emitting it.
Each diagnostic may or many not have an associated category, if it
has one, it is listed in the diagnostic categorization field of the
diagnostic line (in the []'s).
For example, a format string warning will produce these three
renditions based on the setting of this option:
::
t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat]
t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat,1]
t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat,Format String]
This category can be used by clients that want to group diagnostics
by category, so it should be a high level category. We want dozens
of these, not hundreds or thousands of them.
.. _opt_fsave-optimization-record:
**-fsave-optimization-record**
Write optimization remarks to a YAML file.
This option, which defaults to off, controls whether Clang writes
optimization reports to a YAML file. By recording diagnostics in a file,
using a structured YAML format, users can parse or sort the remarks in a
convenient way.
.. _opt_foptimization-record-file:
**-foptimization-record-file**
Control the file to which optimization reports are written.
When optimization reports are being output (see
:ref:`-fsave-optimization-record `), this
option controls the file to which those reports are written.
If this option is not used, optimization records are output to a file named
after the primary file being compiled. If that's "foo.c", for example,
optimization records are output to "foo.opt.yaml".
.. _opt_fdiagnostics-show-hotness:
**-f[no-]diagnostics-show-hotness**
Enable profile hotness information in diagnostic line.
This option controls whether Clang prints the profile hotness associated
with diagnostics in the presence of profile-guided optimization information.
This is currently supported with optimization remarks (see
:ref:`Options to Emit Optimization Reports `). The hotness information
allows users to focus on the hot optimization remarks that are likely to be
more relevant for run-time performance.
For example, in this output, the block containing the callsite of `foo` was
executed 3000 times according to the profile data:
::
s.c:7:10: remark: foo inlined into bar (hotness: 3000) [-Rpass-analysis=inline]
sum += foo(x, x - 2);
^
This option is implied when
:ref:`-fsave-optimization-record ` is used.
Otherwise, it defaults to off.
.. _opt_fdiagnostics-hotness-threshold:
**-fdiagnostics-hotness-threshold**
Prevent optimization remarks from being output if they do not have at least
this hotness value.
This option, which defaults to zero, controls the minimum hotness an
optimization remark would need in order to be output by Clang. This is
currently supported with optimization remarks (see :ref:`Options to Emit
Optimization Reports `) when profile hotness information in
diagnostics is enabled (see
:ref:`-fdiagnostics-show-hotness `).
.. _opt_fdiagnostics-fixit-info:
**-f[no-]diagnostics-fixit-info**
Enable "FixIt" information in the diagnostics output.
This option, which defaults to on, controls whether or not Clang
prints the information on how to fix a specific diagnostic
underneath it when it knows. For example, in this output:
::
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
//
Passing **-fno-diagnostics-fixit-info** will prevent Clang from
printing the "//" line at the end of the message. This information
is useful for users who may not understand what is wrong, but can be
confusing for machine parsing.
.. _opt_fdiagnostics-print-source-range-info:
**-fdiagnostics-print-source-range-info**
Print machine parsable information about source ranges.
This option makes Clang print information about source ranges in a machine
parsable format after the file/line/column number information. The
information is a simple sequence of brace enclosed ranges, where each range
lists the start and end line/column locations. For example, in this output:
::
exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
P = (P-42) + Gamma*4;
~~~~~~ ^ ~~~~~~~
The {}'s are generated by -fdiagnostics-print-source-range-info.
The printed column numbers count bytes from the beginning of the
line; take care if your source contains multibyte characters.
.. option:: -fdiagnostics-parseable-fixits
Print Fix-Its in a machine parseable form.
This option makes Clang print available Fix-Its in a machine
parseable format at the end of diagnostics. The following example
illustrates the format:
::
fix-it:"t.cpp":{7:25-7:29}:"Gamma"
The range printed is a half-open range, so in this example the
characters at column 25 up to but not including column 29 on line 7
in t.cpp should be replaced with the string "Gamma". Either the
range or the replacement string may be empty (representing strict
insertions and strict erasures, respectively). Both the file name
and the insertion string escape backslash (as "\\\\"), tabs (as
"\\t"), newlines (as "\\n"), double quotes(as "\\"") and
non-printable characters (as octal "\\xxx").
The printed column numbers count bytes from the beginning of the
line; take care if your source contains multibyte characters.
.. option:: -fno-elide-type
Turns off elision in template type printing.
The default for template type printing is to elide as many template
arguments as possible, removing those which are the same in both
template types, leaving only the differences. Adding this flag will
print all the template arguments. If supported by the terminal,
highlighting will still appear on differing arguments.
Default:
::
t.cc:4:5: note: candidate function not viable: no known conversion from 'vector>>' to 'vector>>' for 1st argument;
-fno-elide-type:
::
t.cc:4:5: note: candidate function not viable: no known conversion from 'vector>>' to 'vector>>' for 1st argument;
.. option:: -fdiagnostics-show-template-tree
Template type diffing prints a text tree.
For diffing large templated types, this option will cause Clang to
display the templates as an indented text tree, one argument per
line, with differences marked inline. This is compatible with
-fno-elide-type.
Default:
::
t.cc:4:5: note: candidate function not viable: no known conversion from 'vector>>' to 'vector>>' for 1st argument;
With :option:`-fdiagnostics-show-template-tree`:
::
t.cc:4:5: note: candidate function not viable: no known conversion for 1st argument;
vector<
map<
[...],
map<
[float != double],
[...]>>>
.. _cl_diag_warning_groups:
Individual Warning Groups
^^^^^^^^^^^^^^^^^^^^^^^^^
TODO: Generate this from tblgen. Define one anchor per warning group.
.. _opt_wextra-tokens:
.. option:: -Wextra-tokens
Warn about excess tokens at the end of a preprocessor directive.
This option, which defaults to on, enables warnings about extra
tokens at the end of preprocessor directives. For example:
::
test.c:28:8: warning: extra tokens at end of #endif directive [-Wextra-tokens]
#endif bad
^
These extra tokens are not strictly conforming, and are usually best
handled by commenting them out.
.. option:: -Wambiguous-member-template
Warn about unqualified uses of a member template whose name resolves to
another template at the location of the use.
This option, which defaults to on, enables a warning in the
following code:
::
template struct set{};
template struct trait { typedef const T& type; };
struct Value {
template void set(typename trait::type value) {}
};
void foo() {
Value v;
v.set(3.2);
}
C++ [basic.lookup.classref] requires this to be an error, but,
because it's hard to work around, Clang downgrades it to a warning
as an extension.
.. option:: -Wbind-to-temporary-copy
Warn about an unusable copy constructor when binding a reference to a
temporary.
This option enables warnings about binding a
reference to a temporary when the temporary doesn't have a usable
copy constructor. For example:
::
struct NonCopyable {
NonCopyable();
private:
NonCopyable(const NonCopyable&);
};
void foo(const NonCopyable&);
void bar() {
foo(NonCopyable()); // Disallowed in C++98; allowed in C++11.
}
::
struct NonCopyable2 {
NonCopyable2();
NonCopyable2(NonCopyable2&);
};
void foo(const NonCopyable2&);
void bar() {
foo(NonCopyable2()); // Disallowed in C++98; allowed in C++11.
}
Note that if ``NonCopyable2::NonCopyable2()`` has a default argument
whose instantiation produces a compile error, that error will still
be a hard error in C++98 mode even if this warning is turned off.
Options to Control Clang Crash Diagnostics
------------------------------------------
As unbelievable as it may sound, Clang does crash from time to time.
Generally, this only occurs to those living on the `bleeding
edge `_. Clang goes to great
lengths to assist you in filing a bug report. Specifically, Clang
generates preprocessed source file(s) and associated run script(s) upon
a crash. These files should be attached to a bug report to ease
reproducibility of the failure. Below are the command line options to
control the crash diagnostics.
.. option:: -fno-crash-diagnostics
Disable auto-generation of preprocessed source files during a clang crash.
The -fno-crash-diagnostics flag can be helpful for speeding the process
of generating a delta reduced test case.
Clang is also capable of generating preprocessed source file(s) and associated
run script(s) even without a crash. This is specially useful when trying to
generate a reproducer for warnings or errors while using modules.
.. option:: -gen-reproducer
Generates preprocessed source files, a reproducer script and if relevant, a
cache containing: built module pcm's and all headers needed to rebuilt the
same modules.
.. _rpass:
Options to Emit Optimization Reports
------------------------------------
Optimization reports trace, at a high-level, all the major decisions
done by compiler transformations. For instance, when the inliner
decides to inline function ``foo()`` into ``bar()``, or the loop unroller
decides to unroll a loop N times, or the vectorizer decides to
vectorize a loop body.
Clang offers a family of flags which the optimizers can use to emit
a diagnostic in three cases:
1. When the pass makes a transformation (`-Rpass`).
2. When the pass fails to make a transformation (`-Rpass-missed`).
3. When the pass determines whether or not to make a transformation
(`-Rpass-analysis`).
NOTE: Although the discussion below focuses on `-Rpass`, the exact
same options apply to `-Rpass-missed` and `-Rpass-analysis`.
Since there are dozens of passes inside the compiler, each of these flags
take a regular expression that identifies the name of the pass which should
emit the associated diagnostic. For example, to get a report from the inliner,
compile the code with:
.. code-block:: console
$ clang -O2 -Rpass=inline code.cc -o code
code.cc:4:25: remark: foo inlined into bar [-Rpass=inline]
int bar(int j) { return foo(j, j - 2); }
^
Note that remarks from the inliner are identified with `[-Rpass=inline]`.
To request a report from every optimization pass, you should use
`-Rpass=.*` (in fact, you can use any valid POSIX regular
expression). However, do not expect a report from every transformation
made by the compiler. Optimization remarks do not really make sense
outside of the major transformations (e.g., inlining, vectorization,
loop optimizations) and not every optimization pass supports this
feature.
Note that when using profile-guided optimization information, profile hotness
information can be included in the remarks (see
:ref:`-fdiagnostics-show-hotness `).
Current limitations
^^^^^^^^^^^^^^^^^^^
1. Optimization remarks that refer to function names will display the
mangled name of the function. Since these remarks are emitted by the
back end of the compiler, it does not know anything about the input
language, nor its mangling rules.
2. Some source locations are not displayed correctly. The front end has
a more detailed source location tracking than the locations included
in the debug info (e.g., the front end can locate code inside macro
expansions). However, the locations used by `-Rpass` are
translated from debug annotations. That translation can be lossy,
which results in some remarks having no location information.
Other Options
-------------
Clang options that don't fit neatly into other categories.
.. option:: -MV
When emitting a dependency file, use formatting conventions appropriate
for NMake or Jom. Ignored unless another option causes Clang to emit a
dependency file.
When Clang emits a dependency file (e.g., you supplied the -M option)
most filenames can be written to the file without any special formatting.
Different Make tools will treat different sets of characters as "special"
and use different conventions for telling the Make tool that the character
is actually part of the filename. Normally Clang uses backslash to "escape"
a special character, which is the convention used by GNU Make. The -MV
option tells Clang to put double-quotes around the entire filename, which
is the convention used by NMake and Jom.
Configuration files
-------------------
Configuration files group command-line options and allow all of them to be
specified just by referencing the configuration file. They may be used, for
example, to collect options required to tune compilation for particular
target, such as -L, -I, -l, --sysroot, codegen options, etc.
The command line option `--config` can be used to specify configuration
file in a Clang invocation. For example:
::
clang --config /home/user/cfgs/testing.txt
clang --config debug.cfg
If the provided argument contains a directory separator, it is considered as
a file path, and options are read from that file. Otherwise the argument is
treated as a file name and is searched for sequentially in the directories:
- user directory,
- system directory,
- the directory where Clang executable resides.
Both user and system directories for configuration files are specified during
clang build using CMake parameters, CLANG_CONFIG_FILE_USER_DIR and
CLANG_CONFIG_FILE_SYSTEM_DIR respectively. The first file found is used. It is
an error if the required file cannot be found.
Another way to specify a configuration file is to encode it in executable name.
For example, if the Clang executable is named `armv7l-clang` (it may be a
symbolic link to `clang`), then Clang will search for file `armv7l.cfg` in the
directory where Clang resides.
If a driver mode is specified in invocation, Clang tries to find a file specific
for the specified mode. For example, if the executable file is named
`x86_64-clang-cl`, Clang first looks for `x86_64-cl.cfg` and if it is not found,
looks for `x86_64.cfg`.
If the command line contains options that effectively change target architecture
(these are -m32, -EL, and some others) and the configuration file starts with an
architecture name, Clang tries to load the configuration file for the effective
architecture. For example, invocation:
::
x86_64-clang -m32 abc.c
causes Clang search for a file `i368.cfg` first, and if no such file is found,
Clang looks for the file `x86_64.cfg`.
The configuration file consists of command-line options specified on one or
more lines. Lines composed of whitespace characters only are ignored as well as
lines in which the first non-blank character is `#`. Long options may be split
between several lines by a trailing backslash. Here is example of a
configuration file:
::
# Several options on line
-c --target=x86_64-unknown-linux-gnu
# Long option split between lines
-I/usr/lib/gcc/x86_64-linux-gnu/5.4.0/../../../../\
include/c++/5.4.0
# other config files may be included
@linux.options
Files included by `@file` directives in configuration files are resolved
relative to the including file. For example, if a configuration file
`~/.llvm/target.cfg` contains the directive `@os/linux.opts`, the file
`linux.opts` is searched for in the directory `~/.llvm/os`.
Language and Target-Independent Features
========================================
Controlling Errors and Warnings
-------------------------------
Clang provides a number of ways to control which code constructs cause
it to emit errors and warning messages, and how they are displayed to
the console.
Controlling How Clang Displays Diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
When Clang emits a diagnostic, it includes rich information in the
output, and gives you fine-grain control over which information is
printed. Clang has the ability to print this information, and these are
the options that control it:
#. A file/line/column indicator that shows exactly where the diagnostic
occurs in your code [:ref:`-fshow-column `,
:ref:`-fshow-source-location `].
#. A categorization of the diagnostic as a note, warning, error, or
fatal error.
#. A text string that describes what the problem is.
#. An option that indicates how to control the diagnostic (for
diagnostics that support it)
[:ref:`-fdiagnostics-show-option `].
#. A :ref:`high-level category ` for the diagnostic
for clients that want to group diagnostics by class (for diagnostics
that support it)
[:ref:`-fdiagnostics-show-category `].
#. The line of source code that the issue occurs on, along with a caret
and ranges that indicate the important locations
[:ref:`-fcaret-diagnostics `].
#. "FixIt" information, which is a concise explanation of how to fix the
problem (when Clang is certain it knows)
[:ref:`-fdiagnostics-fixit-info `].
#. A machine-parsable representation of the ranges involved (off by
default)
[:ref:`-fdiagnostics-print-source-range-info `].
For more information please see :ref:`Formatting of
Diagnostics `.
Diagnostic Mappings
^^^^^^^^^^^^^^^^^^^
All diagnostics are mapped into one of these 6 classes:
- Ignored
- Note
- Remark
- Warning
- Error
- Fatal
.. _diagnostics_categories:
Diagnostic Categories
^^^^^^^^^^^^^^^^^^^^^
Though not shown by default, diagnostics may each be associated with a
high-level category. This category is intended to make it possible to
triage builds that produce a large number of errors or warnings in a
grouped way.
Categories are not shown by default, but they can be turned on with the
:ref:`-fdiagnostics-show-category ` option.
When set to "``name``", the category is printed textually in the
diagnostic output. When it is set to "``id``", a category number is
printed. The mapping of category names to category id's can be obtained
by running '``clang --print-diagnostic-categories``'.
Controlling Diagnostics via Command Line Flags
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TODO: -W flags, -pedantic, etc
.. _pragma_gcc_diagnostic:
Controlling Diagnostics via Pragmas
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Clang can also control what diagnostics are enabled through the use of
pragmas in the source code. This is useful for turning off specific
warnings in a section of source code. Clang supports GCC's pragma for
compatibility with existing source code, as well as several extensions.
The pragma may control any warning that can be used from the command
line. Warnings may be set to ignored, warning, error, or fatal. The
following example code will tell Clang or GCC to ignore the -Wall
warnings:
.. code-block:: c
#pragma GCC diagnostic ignored "-Wall"
In addition to all of the functionality provided by GCC's pragma, Clang
also allows you to push and pop the current warning state. This is
particularly useful when writing a header file that will be compiled by
other people, because you don't know what warning flags they build with.
In the below example :option:`-Wextra-tokens` is ignored for only a single line
of code, after which the diagnostics return to whatever state had previously
existed.
.. code-block:: c
#if foo
#endif foo // warning: extra tokens at end of #endif directive
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wextra-tokens"
#if foo
#endif foo // no warning
#pragma clang diagnostic pop
The push and pop pragmas will save and restore the full diagnostic state
of the compiler, regardless of how it was set. That means that it is
possible to use push and pop around GCC compatible diagnostics and Clang
will push and pop them appropriately, while GCC will ignore the pushes
and pops as unknown pragmas. It should be noted that while Clang
supports the GCC pragma, Clang and GCC do not support the exact same set
of warnings, so even when using GCC compatible #pragmas there is no
guarantee that they will have identical behaviour on both compilers.
In addition to controlling warnings and errors generated by the compiler, it is
possible to generate custom warning and error messages through the following
pragmas:
.. code-block:: c
// The following will produce warning messages
#pragma message "some diagnostic message"
#pragma GCC warning "TODO: replace deprecated feature"
// The following will produce an error message
#pragma GCC error "Not supported"
These pragmas operate similarly to the ``#warning`` and ``#error`` preprocessor
directives, except that they may also be embedded into preprocessor macros via
the C99 ``_Pragma`` operator, for example:
.. code-block:: c
#define STR(X) #X
#define DEFER(M,...) M(__VA_ARGS__)
#define CUSTOM_ERROR(X) _Pragma(STR(GCC error(X " at line " DEFER(STR,__LINE__))))
CUSTOM_ERROR("Feature not available");
Controlling Diagnostics in System Headers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Warnings are suppressed when they occur in system headers. By default,
an included file is treated as a system header if it is found in an
include path specified by ``-isystem``, but this can be overridden in
several ways.
The ``system_header`` pragma can be used to mark the current file as
being a system header. No warnings will be produced from the location of
the pragma onwards within the same file.
.. code-block:: c
#if foo
#endif foo // warning: extra tokens at end of #endif directive
#pragma clang system_header
#if foo
#endif foo // no warning
The `--system-header-prefix=` and `--no-system-header-prefix=`
command-line arguments can be used to override whether subsets of an include
path are treated as system headers. When the name in a ``#include`` directive
is found within a header search path and starts with a system prefix, the
header is treated as a system header. The last prefix on the
command-line which matches the specified header name takes precedence.
For instance:
.. code-block:: console
$ clang -Ifoo -isystem bar --system-header-prefix=x/ \
--no-system-header-prefix=x/y/
Here, ``#include "x/a.h"`` is treated as including a system header, even
if the header is found in ``foo``, and ``#include "x/y/b.h"`` is treated
as not including a system header, even if the header is found in
``bar``.
A ``#include`` directive which finds a file relative to the current
directory is treated as including a system header if the including file
is treated as a system header.
.. _diagnostics_enable_everything:
Enabling All Diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In addition to the traditional ``-W`` flags, one can enable **all**
diagnostics by passing :option:`-Weverything`. This works as expected
with
:option:`-Werror`, and also includes the warnings from :option:`-pedantic`.
Note that when combined with :option:`-w` (which disables all warnings), that
flag wins.
Controlling Static Analyzer Diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
While not strictly part of the compiler, the diagnostics from Clang's
`static analyzer `_ can also be
influenced by the user via changes to the source code. See the available
`annotations `_ and the
analyzer's `FAQ
page `_ for more
information.
.. _usersmanual-precompiled-headers:
Precompiled Headers
-------------------
`Precompiled headers `__
are a general approach employed by many compilers to reduce compilation
time. The underlying motivation of the approach is that it is common for
the same (and often large) header files to be included by multiple
source files. Consequently, compile times can often be greatly improved
by caching some of the (redundant) work done by a compiler to process
headers. Precompiled header files, which represent one of many ways to
implement this optimization, are literally files that represent an
on-disk cache that contains the vital information necessary to reduce
some of the work needed to process a corresponding header file. While
details of precompiled headers vary between compilers, precompiled
headers have been shown to be highly effective at speeding up program
compilation on systems with very large system headers (e.g., Mac OS X).
Generating a PCH File
^^^^^^^^^^^^^^^^^^^^^
To generate a PCH file using Clang, one invokes Clang with the
`-x -header` option. This mirrors the interface in GCC
for generating PCH files:
.. code-block:: console
$ gcc -x c-header test.h -o test.h.gch
$ clang -x c-header test.h -o test.h.pch
Using a PCH File
^^^^^^^^^^^^^^^^
A PCH file can then be used as a prefix header when a :option:`-include`
option is passed to ``clang``:
.. code-block:: console
$ clang -include test.h test.c -o test
The ``clang`` driver will first check if a PCH file for ``test.h`` is
available; if so, the contents of ``test.h`` (and the files it includes)
will be processed from the PCH file. Otherwise, Clang falls back to
directly processing the content of ``test.h``. This mirrors the behavior
of GCC.
.. note::
Clang does *not* automatically use PCH files for headers that are directly
included within a source file. For example:
.. code-block:: console
$ clang -x c-header test.h -o test.h.pch
$ cat test.c
#include "test.h"
$ clang test.c -o test
In this example, ``clang`` will not automatically use the PCH file for
``test.h`` since ``test.h`` was included directly in the source file and not
specified on the command line using :option:`-include`.
Relocatable PCH Files
^^^^^^^^^^^^^^^^^^^^^
It is sometimes necessary to build a precompiled header from headers
that are not yet in their final, installed locations. For example, one
might build a precompiled header within the build tree that is then
meant to be installed alongside the headers. Clang permits the creation
of "relocatable" precompiled headers, which are built with a given path
(into the build directory) and can later be used from an installed
location.
To build a relocatable precompiled header, place your headers into a
subdirectory whose structure mimics the installed location. For example,
if you want to build a precompiled header for the header ``mylib.h``
that will be installed into ``/usr/include``, create a subdirectory
``build/usr/include`` and place the header ``mylib.h`` into that
subdirectory. If ``mylib.h`` depends on other headers, then they can be
stored within ``build/usr/include`` in a way that mimics the installed
location.
Building a relocatable precompiled header requires two additional
arguments. First, pass the ``--relocatable-pch`` flag to indicate that
the resulting PCH file should be relocatable. Second, pass
``-isysroot /path/to/build``, which makes all includes for your library
relative to the build directory. For example:
.. code-block:: console
# clang -x c-header --relocatable-pch -isysroot /path/to/build /path/to/build/mylib.h mylib.h.pch
When loading the relocatable PCH file, the various headers used in the
PCH file are found from the system header root. For example, ``mylib.h``
can be found in ``/usr/include/mylib.h``. If the headers are installed
in some other system root, the ``-isysroot`` option can be used provide
a different system root from which the headers will be based. For
example, ``-isysroot /Developer/SDKs/MacOSX10.4u.sdk`` will look for
``mylib.h`` in ``/Developer/SDKs/MacOSX10.4u.sdk/usr/include/mylib.h``.
Relocatable precompiled headers are intended to be used in a limited
number of cases where the compilation environment is tightly controlled
and the precompiled header cannot be generated after headers have been
installed.
.. _controlling-code-generation:
Controlling Code Generation
---------------------------
Clang provides a number of ways to control code generation. The options
are listed below.
**-f[no-]sanitize=check1,check2,...**
Turn on runtime checks for various forms of undefined or suspicious
behavior.
This option controls whether Clang adds runtime checks for various
forms of undefined or suspicious behavior, and is disabled by
default. If a check fails, a diagnostic message is produced at
runtime explaining the problem. The main checks are:
- .. _opt_fsanitize_address:
``-fsanitize=address``:
:doc:`AddressSanitizer`, a memory error
detector.
- .. _opt_fsanitize_thread:
``-fsanitize=thread``: :doc:`ThreadSanitizer`, a data race detector.
- .. _opt_fsanitize_memory:
``-fsanitize=memory``: :doc:`MemorySanitizer`,
a detector of uninitialized reads. Requires instrumentation of all
program code.
- .. _opt_fsanitize_undefined:
``-fsanitize=undefined``: :doc:`UndefinedBehaviorSanitizer`,
a fast and compatible undefined behavior checker.
- ``-fsanitize=dataflow``: :doc:`DataFlowSanitizer`, a general data
flow analysis.
- ``-fsanitize=cfi``: :doc:`control flow integrity `
checks. Requires ``-flto``.
- ``-fsanitize=safe-stack``: :doc:`safe stack `
protection against stack-based memory corruption errors.
There are more fine-grained checks available: see
the :ref:`list ` of specific kinds of
undefined behavior that can be detected and the :ref:`list `
of control flow integrity schemes.
The ``-fsanitize=`` argument must also be provided when linking, in
order to link to the appropriate runtime library.
It is not possible to combine more than one of the ``-fsanitize=address``,
``-fsanitize=thread``, and ``-fsanitize=memory`` checkers in the same
program.
**-f[no-]sanitize-recover=check1,check2,...**
**-f[no-]sanitize-recover=all**
Controls which checks enabled by ``-fsanitize=`` flag are non-fatal.
If the check is fatal, program will halt after the first error
of this kind is detected and error report is printed.
By default, non-fatal checks are those enabled by
:doc:`UndefinedBehaviorSanitizer`,
except for ``-fsanitize=return`` and ``-fsanitize=unreachable``. Some
sanitizers may not support recovery (or not support it by default
e.g. :doc:`AddressSanitizer`), and always crash the program after the issue
is detected.
Note that the ``-fsanitize-trap`` flag has precedence over this flag.
This means that if a check has been configured to trap elsewhere on the
command line, or if the check traps by default, this flag will not have
any effect unless that sanitizer's trapping behavior is disabled with
``-fno-sanitize-trap``.
For example, if a command line contains the flags ``-fsanitize=undefined
-fsanitize-trap=undefined``, the flag ``-fsanitize-recover=alignment``
will have no effect on its own; it will need to be accompanied by
``-fno-sanitize-trap=alignment``.
**-f[no-]sanitize-trap=check1,check2,...**
Controls which checks enabled by the ``-fsanitize=`` flag trap. This
option is intended for use in cases where the sanitizer runtime cannot
be used (for instance, when building libc or a kernel module), or where
the binary size increase caused by the sanitizer runtime is a concern.
This flag is only compatible with :doc:`control flow integrity
` schemes and :doc:`UndefinedBehaviorSanitizer`
checks other than ``vptr``. If this flag
is supplied together with ``-fsanitize=undefined``, the ``vptr`` sanitizer
will be implicitly disabled.
This flag is enabled by default for sanitizers in the ``cfi`` group.
.. option:: -fsanitize-blacklist=/path/to/blacklist/file
Disable or modify sanitizer checks for objects (source files, functions,
variables, types) listed in the file. See
:doc:`SanitizerSpecialCaseList` for file format description.
.. option:: -fno-sanitize-blacklist
Don't use blacklist file, if it was specified earlier in the command line.
**-f[no-]sanitize-coverage=[type,features,...]**
Enable simple code coverage in addition to certain sanitizers.
See :doc:`SanitizerCoverage` for more details.
**-f[no-]sanitize-stats**
Enable simple statistics gathering for the enabled sanitizers.
See :doc:`SanitizerStats` for more details.
.. option:: -fsanitize-undefined-trap-on-error
Deprecated alias for ``-fsanitize-trap=undefined``.
.. option:: -fsanitize-cfi-cross-dso
Enable cross-DSO control flow integrity checks. This flag modifies
the behavior of sanitizers in the ``cfi`` group to allow checking
of cross-DSO virtual and indirect calls.
.. option:: -fsanitize-cfi-icall-generalize-pointers
Generalize pointers in return and argument types in function type signatures
checked by Control Flow Integrity indirect call checking. See
:doc:`ControlFlowIntegrity` for more details.
.. option:: -fstrict-vtable-pointers
Enable optimizations based on the strict rules for overwriting polymorphic
C++ objects, i.e. the vptr is invariant during an object's lifetime.
This enables better devirtualization. Turned off by default, because it is
still experimental.
.. option:: -ffast-math
Enable fast-math mode. This defines the ``__FAST_MATH__`` preprocessor
macro, and lets the compiler make aggressive, potentially-lossy assumptions
about floating-point math. These include:
* Floating-point math obeys regular algebraic rules for real numbers (e.g.
``+`` and ``*`` are associative, ``x/y == x * (1/y)``, and
``(a + b) * c == a * c + b * c``),
* operands to floating-point operations are not equal to ``NaN`` and
``Inf``, and
* ``+0`` and ``-0`` are interchangeable.
.. option:: -fdenormal-fp-math=[values]
Select which denormal numbers the code is permitted to require.
Valid values are: ``ieee``, ``preserve-sign``, and ``positive-zero``,
which correspond to IEEE 754 denormal numbers, the sign of a
flushed-to-zero number is preserved in the sign of 0, denormals are
flushed to positive zero, respectively.
.. option:: -f[no-]strict-float-cast-overflow
When a floating-point value is not representable in a destination integer
type, the code has undefined behavior according to the language standard.
By default, Clang will not guarantee any particular result in that case.
With the 'no-strict' option, Clang attempts to match the overflowing behavior
of the target's native float-to-int conversion instructions.
.. option:: -fwhole-program-vtables
Enable whole-program vtable optimizations, such as single-implementation
devirtualization and virtual constant propagation, for classes with
:doc:`hidden LTO visibility `. Requires ``-flto``.
.. option:: -fforce-emit-vtables
In order to improve devirtualization, forces emitting of vtables even in
modules where it isn't necessary. It causes more inline virtual functions
to be emitted.
.. option:: -fno-assume-sane-operator-new
Don't assume that the C++'s new operator is sane.
This option tells the compiler to do not assume that C++'s global
new operator will always return a pointer that does not alias any
other pointer when the function returns.
.. option:: -ftrap-function=[name]
Instruct code generator to emit a function call to the specified
function name for ``__builtin_trap()``.
LLVM code generator translates ``__builtin_trap()`` to a trap
instruction if it is supported by the target ISA. Otherwise, the
builtin is translated into a call to ``abort``. If this option is
set, then the code generator will always lower the builtin to a call
to the specified function regardless of whether the target ISA has a
trap instruction. This option is useful for environments (e.g.
deeply embedded) where a trap cannot be properly handled, or when
some custom behavior is desired.
.. option:: -ftls-model=[model]
Select which TLS model to use.
Valid values are: ``global-dynamic``, ``local-dynamic``,
``initial-exec`` and ``local-exec``. The default value is
``global-dynamic``. The compiler may use a different model if the
selected model is not supported by the target, or if a more
efficient model can be used. The TLS model can be overridden per
variable using the ``tls_model`` attribute.
.. option:: -femulated-tls
Select emulated TLS model, which overrides all -ftls-model choices.
In emulated TLS mode, all access to TLS variables are converted to
calls to __emutls_get_address in the runtime library.
.. option:: -mhwdiv=[values]
Select the ARM modes (arm or thumb) that support hardware division
instructions.
Valid values are: ``arm``, ``thumb`` and ``arm,thumb``.
This option is used to indicate which mode (arm or thumb) supports
hardware division instructions. This only applies to the ARM
architecture.
.. option:: -m[no-]crc
Enable or disable CRC instructions.
This option is used to indicate whether CRC instructions are to
be generated. This only applies to the ARM architecture.
CRC instructions are enabled by default on ARMv8.
.. option:: -mgeneral-regs-only
Generate code which only uses the general purpose registers.
This option restricts the generated code to use general registers
only. This only applies to the AArch64 architecture.
.. option:: -mcompact-branches=[values]
Control the usage of compact branches for MIPSR6.
Valid values are: ``never``, ``optimal`` and ``always``.
The default value is ``optimal`` which generates compact branches
when a delay slot cannot be filled. ``never`` disables the usage of
compact branches and ``always`` generates compact branches whenever
possible.
**-f[no-]max-type-align=[number]**
Instruct the code generator to not enforce a higher alignment than the given
number (of bytes) when accessing memory via an opaque pointer or reference.
This cap is ignored when directly accessing a variable or when the pointee
type has an explicit “aligned” attribute.
The value should usually be determined by the properties of the system allocator.
Some builtin types, especially vector types, have very high natural alignments;
when working with values of those types, Clang usually wants to use instructions
that take advantage of that alignment. However, many system allocators do
not promise to return memory that is more than 8-byte or 16-byte-aligned. Use
this option to limit the alignment that the compiler can assume for an arbitrary
pointer, which may point onto the heap.
This option does not affect the ABI alignment of types; the layout of structs and
unions and the value returned by the alignof operator remain the same.
This option can be overridden on a case-by-case basis by putting an explicit
“aligned” alignment on a struct, union, or typedef. For example:
.. code-block:: console
#include
// Make an aligned typedef of the AVX-512 16-int vector type.
typedef __v16si __aligned_v16si __attribute__((aligned(64)));
void initialize_vector(__aligned_v16si *v) {
// The compiler may assume that ‘v’ is 64-byte aligned, regardless of the
// value of -fmax-type-align.
}
.. option:: -faddrsig, -fno-addrsig
Controls whether Clang emits an address-significance table into the object
file. Address-significance tables allow linkers to implement `safe ICF
`_ without the false
positives that can result from other implementation techniques such as
relocation scanning. Address-significance tables are enabled by default
on ELF targets when using the integrated assembler. This flag currently
only has an effect on ELF targets.
Profile Guided Optimization
---------------------------
Profile information enables better optimization. For example, knowing that a
branch is taken very frequently helps the compiler make better decisions when
ordering basic blocks. Knowing that a function ``foo`` is called more
frequently than another function ``bar`` helps the inliner. Optimization
levels ``-O2`` and above are recommended for use of profile guided optimization.
Clang supports profile guided optimization with two different kinds of
profiling. A sampling profiler can generate a profile with very low runtime
overhead, or you can build an instrumented version of the code that collects
more detailed profile information. Both kinds of profiles can provide execution
counts for instructions in the code and information on branches taken and
function invocation.
Regardless of which kind of profiling you use, be careful to collect profiles
by running your code with inputs that are representative of the typical
behavior. Code that is not exercised in the profile will be optimized as if it
is unimportant, and the compiler may make poor optimization choices for code
that is disproportionately used while profiling.
Differences Between Sampling and Instrumentation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Although both techniques are used for similar purposes, there are important
differences between the two:
1. Profile data generated with one cannot be used by the other, and there is no
conversion tool that can convert one to the other. So, a profile generated
via ``-fprofile-instr-generate`` must be used with ``-fprofile-instr-use``.
Similarly, sampling profiles generated by external profilers must be
converted and used with ``-fprofile-sample-use``.
2. Instrumentation profile data can be used for code coverage analysis and
optimization.
3. Sampling profiles can only be used for optimization. They cannot be used for
code coverage analysis. Although it would be technically possible to use
sampling profiles for code coverage, sample-based profiles are too
coarse-grained for code coverage purposes; it would yield poor results.
4. Sampling profiles must be generated by an external tool. The profile
generated by that tool must then be converted into a format that can be read
by LLVM. The section on sampling profilers describes one of the supported
sampling profile formats.
Using Sampling Profilers
^^^^^^^^^^^^^^^^^^^^^^^^
Sampling profilers are used to collect runtime information, such as
hardware counters, while your application executes. They are typically
very efficient and do not incur a large runtime overhead. The
sample data collected by the profiler can be used during compilation
to determine what the most executed areas of the code are.
Using the data from a sample profiler requires some changes in the way
a program is built. Before the compiler can use profiling information,
the code needs to execute under the profiler. The following is the
usual build cycle when using sample profilers for optimization:
1. Build the code with source line table information. You can use all the
usual build flags that you always build your application with. The only
requirement is that you add ``-gline-tables-only`` or ``-g`` to the
command line. This is important for the profiler to be able to map
instructions back to source line locations.
.. code-block:: console
$ clang++ -O2 -gline-tables-only code.cc -o code
2. Run the executable under a sampling profiler. The specific profiler
you use does not really matter, as long as its output can be converted
into the format that the LLVM optimizer understands. Currently, there
exists a conversion tool for the Linux Perf profiler
(https://perf.wiki.kernel.org/), so these examples assume that you
are using Linux Perf to profile your code.
.. code-block:: console
$ perf record -b ./code
Note the use of the ``-b`` flag. This tells Perf to use the Last Branch
Record (LBR) to record call chains. While this is not strictly required,
it provides better call information, which improves the accuracy of
the profile data.
3. Convert the collected profile data to LLVM's sample profile format.
This is currently supported via the AutoFDO converter ``create_llvm_prof``.
It is available at http://github.com/google/autofdo. Once built and
installed, you can convert the ``perf.data`` file to LLVM using
the command:
.. code-block:: console
$ create_llvm_prof --binary=./code --out=code.prof
This will read ``perf.data`` and the binary file ``./code`` and emit
the profile data in ``code.prof``. Note that if you ran ``perf``
without the ``-b`` flag, you need to use ``--use_lbr=false`` when
calling ``create_llvm_prof``.
4. Build the code again using the collected profile. This step feeds
the profile back to the optimizers. This should result in a binary
that executes faster than the original one. Note that you are not
required to build the code with the exact same arguments that you
used in the first step. The only requirement is that you build the code
with ``-gline-tables-only`` and ``-fprofile-sample-use``.
.. code-block:: console
$ clang++ -O2 -gline-tables-only -fprofile-sample-use=code.prof code.cc -o code
Sample Profile Formats
""""""""""""""""""""""
Since external profilers generate profile data in a variety of custom formats,
the data generated by the profiler must be converted into a format that can be
read by the backend. LLVM supports three different sample profile formats:
1. ASCII text. This is the easiest one to generate. The file is divided into
sections, which correspond to each of the functions with profile
information. The format is described below. It can also be generated from
the binary or gcov formats using the ``llvm-profdata`` tool.
2. Binary encoding. This uses a more efficient encoding that yields smaller
profile files. This is the format generated by the ``create_llvm_prof`` tool
in http://github.com/google/autofdo.
3. GCC encoding. This is based on the gcov format, which is accepted by GCC. It
is only interesting in environments where GCC and Clang co-exist. This
encoding is only generated by the ``create_gcov`` tool in
http://github.com/google/autofdo. It can be read by LLVM and
``llvm-profdata``, but it cannot be generated by either.
If you are using Linux Perf to generate sampling profiles, you can use the
conversion tool ``create_llvm_prof`` described in the previous section.
Otherwise, you will need to write a conversion tool that converts your
profiler's native format into one of these three.
Sample Profile Text Format
""""""""""""""""""""""""""
This section describes the ASCII text format for sampling profiles. It is,
arguably, the easiest one to generate. If you are interested in generating any
of the other two, consult the ``ProfileData`` library in LLVM's source tree
(specifically, ``include/llvm/ProfileData/SampleProfReader.h``).
.. code-block:: console
function1:total_samples:total_head_samples
offset1[.discriminator]: number_of_samples [fn1:num fn2:num ... ]
offset2[.discriminator]: number_of_samples [fn3:num fn4:num ... ]
...
offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ]
offsetA[.discriminator]: fnA:num_of_total_samples
offsetA1[.discriminator]: number_of_samples [fn7:num fn8:num ... ]
offsetA1[.discriminator]: number_of_samples [fn9:num fn10:num ... ]
offsetB[.discriminator]: fnB:num_of_total_samples
offsetB1[.discriminator]: number_of_samples [fn11:num fn12:num ... ]
This is a nested tree in which the indentation represents the nesting level
of the inline stack. There are no blank lines in the file. And the spacing
within a single line is fixed. Additional spaces will result in an error
while reading the file.
Any line starting with the '#' character is completely ignored.
Inlined calls are represented with indentation. The Inline stack is a
stack of source locations in which the top of the stack represents the
leaf function, and the bottom of the stack represents the actual
symbol to which the instruction belongs.
Function names must be mangled in order for the profile loader to
match them in the current translation unit. The two numbers in the
function header specify how many total samples were accumulated in the
function (first number), and the total number of samples accumulated
in the prologue of the function (second number). This head sample
count provides an indicator of how frequently the function is invoked.
There are two types of lines in the function body.
- Sampled line represents the profile information of a source location.
``offsetN[.discriminator]: number_of_samples [fn5:num fn6:num ... ]``
- Callsite line represents the profile information of an inlined callsite.
``offsetA[.discriminator]: fnA:num_of_total_samples``
Each sampled line may contain several items. Some are optional (marked
below):
a. Source line offset. This number represents the line number
in the function where the sample was collected. The line number is
always relative to the line where symbol of the function is
defined. So, if the function has its header at line 280, the offset
13 is at line 293 in the file.
Note that this offset should never be a negative number. This could
happen in cases like macros. The debug machinery will register the
line number at the point of macro expansion. So, if the macro was
expanded in a line before the start of the function, the profile
converter should emit a 0 as the offset (this means that the optimizers
will not be able to associate a meaningful weight to the instructions
in the macro).
b. [OPTIONAL] Discriminator. This is used if the sampled program
was compiled with DWARF discriminator support
(http://wiki.dwarfstd.org/index.php?title=Path_Discriminators).
DWARF discriminators are unsigned integer values that allow the
compiler to distinguish between multiple execution paths on the
same source line location.
For example, consider the line of code ``if (cond) foo(); else bar();``.
If the predicate ``cond`` is true 80% of the time, then the edge
into function ``foo`` should be considered to be taken most of the
time. But both calls to ``foo`` and ``bar`` are at the same source
line, so a sample count at that line is not sufficient. The
compiler needs to know which part of that line is taken more
frequently.
This is what discriminators provide. In this case, the calls to
``foo`` and ``bar`` will be at the same line, but will have
different discriminator values. This allows the compiler to correctly
set edge weights into ``foo`` and ``bar``.
c. Number of samples. This is an integer quantity representing the
number of samples collected by the profiler at this source
location.
d. [OPTIONAL] Potential call targets and samples. If present, this
line contains a call instruction. This models both direct and
number of samples. For example,
.. code-block:: console
130: 7 foo:3 bar:2 baz:7
The above means that at relative line offset 130 there is a call
instruction that calls one of ``foo()``, ``bar()`` and ``baz()``,
with ``baz()`` being the relatively more frequently called target.
As an example, consider a program with the call chain ``main -> foo -> bar``.
When built with optimizations enabled, the compiler may inline the
calls to ``bar`` and ``foo`` inside ``main``. The generated profile
could then be something like this:
.. code-block:: console
main:35504:0
1: _Z3foov:35504
2: _Z32bari:31977
1.1: 31977
2: 0
This profile indicates that there were a total of 35,504 samples
collected in main. All of those were at line 1 (the call to ``foo``).
Of those, 31,977 were spent inside the body of ``bar``. The last line
of the profile (``2: 0``) corresponds to line 2 inside ``main``. No
samples were collected there.
Profiling with Instrumentation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Clang also supports profiling via instrumentation. This requires building a
special instrumented version of the code and has some runtime
overhead during the profiling, but it provides more detailed results than a
sampling profiler. It also provides reproducible results, at least to the
extent that the code behaves consistently across runs.
Here are the steps for using profile guided optimization with
instrumentation:
1. Build an instrumented version of the code by compiling and linking with the
``-fprofile-instr-generate`` option.
.. code-block:: console
$ clang++ -O2 -fprofile-instr-generate code.cc -o code
2. Run the instrumented executable with inputs that reflect the typical usage.
By default, the profile data will be written to a ``default.profraw`` file
in the current directory. You can override that default by using option
``-fprofile-instr-generate=`` or by setting the ``LLVM_PROFILE_FILE``
environment variable to specify an alternate file. If non-default file name
is specified by both the environment variable and the command line option,
the environment variable takes precedence. The file name pattern specified
can include different modifiers: ``%p``, ``%h``, and ``%m``.
Any instance of ``%p`` in that file name will be replaced by the process
ID, so that you can easily distinguish the profile output from multiple
runs.
.. code-block:: console
$ LLVM_PROFILE_FILE="code-%p.profraw" ./code
The modifier ``%h`` can be used in scenarios where the same instrumented
binary is run in multiple different host machines dumping profile data
to a shared network based storage. The ``%h`` specifier will be substituted
with the hostname so that profiles collected from different hosts do not
clobber each other.
While the use of ``%p`` specifier can reduce the likelihood for the profiles
dumped from different processes to clobber each other, such clobbering can still
happen because of the ``pid`` re-use by the OS. Another side-effect of using
``%p`` is that the storage requirement for raw profile data files is greatly
increased. To avoid issues like this, the ``%m`` specifier can used in the profile
name. When this specifier is used, the profiler runtime will substitute ``%m``
with a unique integer identifier associated with the instrumented binary. Additionally,
multiple raw profiles dumped from different processes that share a file system (can be
on different hosts) will be automatically merged by the profiler runtime during the
dumping. If the program links in multiple instrumented shared libraries, each library
will dump the profile data into its own profile data file (with its unique integer
id embedded in the profile name). Note that the merging enabled by ``%m`` is for raw
profile data generated by profiler runtime. The resulting merged "raw" profile data
file still needs to be converted to a different format expected by the compiler (
see step 3 below).
.. code-block:: console
$ LLVM_PROFILE_FILE="code-%m.profraw" ./code
3. Combine profiles from multiple runs and convert the "raw" profile format to
the input expected by clang. Use the ``merge`` command of the
``llvm-profdata`` tool to do this.
.. code-block:: console
$ llvm-profdata merge -output=code.profdata code-*.profraw
Note that this step is necessary even when there is only one "raw" profile,
since the merge operation also changes the file format.
4. Build the code again using the ``-fprofile-instr-use`` option to specify the
collected profile data.
.. code-block:: console
$ clang++ -O2 -fprofile-instr-use=code.profdata code.cc -o code
You can repeat step 4 as often as you like without regenerating the
profile. As you make changes to your code, clang may no longer be able to
use the profile data. It will warn you when this happens.
Profile generation using an alternative instrumentation method can be
controlled by the GCC-compatible flags ``-fprofile-generate`` and
``-fprofile-use``. Although these flags are semantically equivalent to
their GCC counterparts, they *do not* handle GCC-compatible profiles.
They are only meant to implement GCC's semantics with respect to
profile creation and use.
.. option:: -fprofile-generate[=]
The ``-fprofile-generate`` and ``-fprofile-generate=`` flags will use
an alternative instrumentation method for profile generation. When
given a directory name, it generates the profile file
``default_%m.profraw`` in the directory named ``dirname`` if specified.
If ``dirname`` does not exist, it will be created at runtime. ``%m`` specifier
will be substituted with a unique id documented in step 2 above. In other words,
with ``-fprofile-generate[=]`` option, the "raw" profile data automatic
merging is turned on by default, so there will no longer any risk of profile
clobbering from different running processes. For example,
.. code-block:: console
$ clang++ -O2 -fprofile-generate=yyy/zzz code.cc -o code
When ``code`` is executed, the profile will be written to the file
``yyy/zzz/default_xxxx.profraw``.
To generate the profile data file with the compiler readable format, the
``llvm-profdata`` tool can be used with the profile directory as the input:
.. code-block:: console
$ llvm-profdata merge -output=code.profdata yyy/zzz/
If the user wants to turn off the auto-merging feature, or simply override the
the profile dumping path specified at command line, the environment variable
``LLVM_PROFILE_FILE`` can still be used to override
the directory and filename for the profile file at runtime.
.. option:: -fprofile-use[=]
Without any other arguments, ``-fprofile-use`` behaves identically to
``-fprofile-instr-use``. Otherwise, if ``pathname`` is the full path to a
profile file, it reads from that file. If ``pathname`` is a directory name,
it reads from ``pathname/default.profdata``.
Disabling Instrumentation
^^^^^^^^^^^^^^^^^^^^^^^^^
In certain situations, it may be useful to disable profile generation or use
for specific files in a build, without affecting the main compilation flags
used for the other files in the project.
In these cases, you can use the flag ``-fno-profile-instr-generate`` (or
``-fno-profile-generate``) to disable profile generation, and
``-fno-profile-instr-use`` (or ``-fno-profile-use``) to disable profile use.
Note that these flags should appear after the corresponding profile
flags to have an effect.
+.. _profile_remapping:
+
Profile remapping
^^^^^^^^^^^^^^^^^
When the program is compiled after a change that affects many symbol names,
pre-existing profile data may no longer match the program. For example:
* switching from libstdc++ to libc++ will result in the mangled names of all
functions taking standard library types to change
* renaming a widely-used type in C++ will result in the mangled names of all
functions that have parameters involving that type to change
* moving from a 32-bit compilation to a 64-bit compilation may change the
underlying type of ``size_t`` and similar types, resulting in changes to
manglings
Clang allows use of a profile remapping file to specify that such differences
in mangled names should be ignored when matching the profile data against the
program.
.. option:: -fprofile-remapping-file=
Specifies a file containing profile remapping information, that will be
used to match mangled names in the profile data to mangled names in the
program.
The profile remapping file is a text file containing lines of the form
.. code-block:: text
fragmentkind fragment1 fragment2
where ``fragmentkind`` is one of ``name``, ``type``, or ``encoding``,
indicating whether the following mangled name fragments are
<`name `_>s,
<`type `_>s, or
<`encoding `_>s,
respectively.
Blank lines and lines starting with ``#`` are ignored.
For convenience, built-in s such as ``St`` and ``Ss``
are accepted as s (even though they technically are not s).
For example, to specify that ``absl::string_view`` and ``std::string_view``
should be treated as equivalent when matching profile data, the following
remapping file could be used:
.. code-block:: text
# absl::string_view is considered equivalent to std::string_view
type N4absl11string_viewE St17basic_string_viewIcSt11char_traitsIcEE
# std:: might be std::__1:: in libc++ or std::__cxx11:: in libstdc++
name 3std St3__1
name 3std St7__cxx11
Matching profile data using a profile remapping file is supported on a
best-effort basis. For example, information regarding indirect call targets is
currently not remapped. For best results, you are encouraged to generate new
profile data matching the updated program, or to remap the profile data
using the ``llvm-cxxmap`` and ``llvm-profdata merge`` tools.
.. note::
Profile data remapping support is currently only implemented for LLVM's
new pass manager, which can be enabled with
``-fexperimental-new-pass-manager``.
.. note::
Profile data remapping is currently only supported for C++ mangled names
following the Itanium C++ ABI mangling scheme. This covers all C++ targets
supported by Clang other than Windows.
GCOV-based Profiling
--------------------
GCOV is a test coverage program, it helps to know how often a line of code
is executed. When instrumenting the code with ``--coverage`` option, some
counters are added for each edge linking basic blocks.
At compile time, gcno files are generated containing information about
blocks and edges between them. At runtime the counters are incremented and at
exit the counters are dumped in gcda files.
The tool ``llvm-cov gcov`` will parse gcno, gcda and source files to generate
a report ``.c.gcov``.
.. option:: -fprofile-filter-files=[regexes]
Define a list of regexes separated by a semi-colon.
If a file name matches any of the regexes then the file is instrumented.
.. code-block:: console
$ clang --coverage -fprofile-filter-files=".*\.c$" foo.c
For example, this will only instrument files finishing with ``.c``, skipping ``.h`` files.
.. option:: -fprofile-exclude-files=[regexes]
Define a list of regexes separated by a semi-colon.
If a file name doesn't match all the regexes then the file is instrumented.
.. code-block:: console
$ clang --coverage -fprofile-exclude-files="^/usr/include/.*$" foo.c
For example, this will instrument all the files except the ones in ``/usr/include``.
If both options are used then a file is instrumented if its name matches any
of the regexes from ``-fprofile-filter-list`` and doesn't match all the regexes
from ``-fprofile-exclude-list``.
.. code-block:: console
$ clang --coverage -fprofile-exclude-files="^/usr/include/.*$" \
-fprofile-filter-files="^/usr/.*$"
In that case ``/usr/foo/oof.h`` is instrumented since it matches the filter regex and
doesn't match the exclude regex, but ``/usr/include/foo.h`` doesn't since it matches
the exclude regex.
Controlling Debug Information
-----------------------------
Controlling Size of Debug Information
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Debug info kind generated by Clang can be set by one of the flags listed
below. If multiple flags are present, the last one is used.
.. option:: -g0
Don't generate any debug info (default).
.. option:: -gline-tables-only
Generate line number tables only.
This kind of debug info allows to obtain stack traces with function names,
file names and line numbers (by such tools as ``gdb`` or ``addr2line``). It
doesn't contain any other data (e.g. description of local variables or
function parameters).
.. option:: -fstandalone-debug
Clang supports a number of optimizations to reduce the size of debug
information in the binary. They work based on the assumption that
the debug type information can be spread out over multiple
compilation units. For instance, Clang will not emit type
definitions for types that are not needed by a module and could be
replaced with a forward declaration. Further, Clang will only emit
type info for a dynamic C++ class in the module that contains the
vtable for the class.
The **-fstandalone-debug** option turns off these optimizations.
This is useful when working with 3rd-party libraries that don't come
with debug information. Note that Clang will never emit type
information for types that are not referenced at all by the program.
.. option:: -fno-standalone-debug
On Darwin **-fstandalone-debug** is enabled by default. The
**-fno-standalone-debug** option can be used to get to turn on the
vtable-based optimization described above.
.. option:: -g
Generate complete debug info.
Controlling Macro Debug Info Generation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Debug info for C preprocessor macros increases the size of debug information in
the binary. Macro debug info generated by Clang can be controlled by the flags
listed below.
.. option:: -fdebug-macro
Generate debug info for preprocessor macros. This flag is discarded when
**-g0** is enabled.
.. option:: -fno-debug-macro
Do not generate debug info for preprocessor macros (default).
Controlling Debugger "Tuning"
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
While Clang generally emits standard DWARF debug info (http://dwarfstd.org),
different debuggers may know how to take advantage of different specific DWARF
features. You can "tune" the debug info for one of several different debuggers.
.. option:: -ggdb, -glldb, -gsce
Tune the debug info for the ``gdb``, ``lldb``, or Sony PlayStation\ |reg|
debugger, respectively. Each of these options implies **-g**. (Therefore, if
you want both **-gline-tables-only** and debugger tuning, the tuning option
must come first.)
Controlling LLVM IR Output
--------------------------
Controlling Value Names in LLVM IR
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Emitting value names in LLVM IR increases the size and verbosity of the IR.
By default, value names are only emitted in assertion-enabled builds of Clang.
However, when reading IR it can be useful to re-enable the emission of value
names to improve readability.
.. option:: -fdiscard-value-names
Discard value names when generating LLVM IR.
.. option:: -fno-discard-value-names
Do not discard value names when generating LLVM IR. This option can be used
to re-enable names for release builds of Clang.
Comment Parsing Options
-----------------------
Clang parses Doxygen and non-Doxygen style documentation comments and attaches
them to the appropriate declaration nodes. By default, it only parses
Doxygen-style comments and ignores ordinary comments starting with ``//`` and
``/*``.
.. option:: -Wdocumentation
Emit warnings about use of documentation comments. This warning group is off
by default.
This includes checking that ``\param`` commands name parameters that actually
present in the function signature, checking that ``\returns`` is used only on
functions that actually return a value etc.
.. option:: -Wno-documentation-unknown-command
Don't warn when encountering an unknown Doxygen command.
.. option:: -fparse-all-comments
Parse all comments as documentation comments (including ordinary comments
starting with ``//`` and ``/*``).
.. option:: -fcomment-block-commands=[commands]
Define custom documentation commands as block commands. This allows Clang to
construct the correct AST for these custom commands, and silences warnings
about unknown commands. Several commands must be separated by a comma
*without trailing space*; e.g. ``-fcomment-block-commands=foo,bar`` defines
custom commands ``\foo`` and ``\bar``.
It is also possible to use ``-fcomment-block-commands`` several times; e.g.
``-fcomment-block-commands=foo -fcomment-block-commands=bar`` does the same
as above.
.. _c:
C Language Features
===================
The support for standard C in clang is feature-complete except for the
C99 floating-point pragmas.
Extensions supported by clang
-----------------------------
See :doc:`LanguageExtensions`.
Differences between various standard modes
------------------------------------------
clang supports the -std option, which changes what language mode clang
uses. The supported modes for C are c89, gnu89, c99, gnu99, c11, gnu11,
c17, gnu17, and various aliases for those modes. If no -std option is
specified, clang defaults to gnu11 mode. Many C99 and C11 features are
supported in earlier modes as a conforming extension, with a warning. Use
``-pedantic-errors`` to request an error if a feature from a later standard
revision is used in an earlier mode.
Differences between all ``c*`` and ``gnu*`` modes:
- ``c*`` modes define "``__STRICT_ANSI__``".
- Target-specific defines not prefixed by underscores, like "linux",
are defined in ``gnu*`` modes.
- Trigraphs default to being off in ``gnu*`` modes; they can be enabled by
the -trigraphs option.
- The parser recognizes "asm" and "typeof" as keywords in ``gnu*`` modes;
the variants "``__asm__``" and "``__typeof__``" are recognized in all
modes.
- The Apple "blocks" extension is recognized by default in ``gnu*`` modes
on some platforms; it can be enabled in any mode with the "-fblocks"
option.
- Arrays that are VLA's according to the standard, but which can be
constant folded by the frontend are treated as fixed size arrays.
This occurs for things like "int X[(1, 2)];", which is technically a
VLA. ``c*`` modes are strictly compliant and treat these as VLAs.
Differences between ``*89`` and ``*99`` modes:
- The ``*99`` modes default to implementing "inline" as specified in C99,
while the ``*89`` modes implement the GNU version. This can be
overridden for individual functions with the ``__gnu_inline__``
attribute.
- Digraphs are not recognized in c89 mode.
- The scope of names defined inside a "for", "if", "switch", "while",
or "do" statement is different. (example: "``if ((struct x {int
x;}*)0) {}``".)
- ``__STDC_VERSION__`` is not defined in ``*89`` modes.
- "inline" is not recognized as a keyword in c89 mode.
- "restrict" is not recognized as a keyword in ``*89`` modes.
- Commas are allowed in integer constant expressions in ``*99`` modes.
- Arrays which are not lvalues are not implicitly promoted to pointers
in ``*89`` modes.
- Some warnings are different.
Differences between ``*99`` and ``*11`` modes:
- Warnings for use of C11 features are disabled.
- ``__STDC_VERSION__`` is defined to ``201112L`` rather than ``199901L``.
Differences between ``*11`` and ``*17`` modes:
- ``__STDC_VERSION__`` is defined to ``201710L`` rather than ``201112L``.
GCC extensions not implemented yet
----------------------------------
clang tries to be compatible with gcc as much as possible, but some gcc
extensions are not implemented yet:
- clang does not support decimal floating point types (``_Decimal32`` and
friends) or fixed-point types (``_Fract`` and friends); nobody has
expressed interest in these features yet, so it's hard to say when
they will be implemented.
- clang does not support nested functions; this is a complex feature
which is infrequently used, so it is unlikely to be implemented
anytime soon. In C++11 it can be emulated by assigning lambda
functions to local variables, e.g:
.. code-block:: cpp
auto const local_function = [&](int parameter) {
// Do something
};
...
local_function(1);
- clang only supports global register variables when the register specified
is non-allocatable (e.g. the stack pointer). Support for general global
register variables is unlikely to be implemented soon because it requires
additional LLVM backend support.
- clang does not support static initialization of flexible array
members. This appears to be a rarely used extension, but could be
implemented pending user demand.
- clang does not support
``__builtin_va_arg_pack``/``__builtin_va_arg_pack_len``. This is
used rarely, but in some potentially interesting places, like the
glibc headers, so it may be implemented pending user demand. Note
that because clang pretends to be like GCC 4.2, and this extension
was introduced in 4.3, the glibc headers will not try to use this
extension with clang at the moment.
- clang does not support the gcc extension for forward-declaring
function parameters; this has not shown up in any real-world code
yet, though, so it might never be implemented.
This is not a complete list; if you find an unsupported extension
missing from this list, please send an e-mail to cfe-dev. This list
currently excludes C++; see :ref:`C++ Language Features `. Also, this
list does not include bugs in mostly-implemented features; please see
the `bug
tracker `_
for known existing bugs (FIXME: Is there a section for bug-reporting
guidelines somewhere?).
Intentionally unsupported GCC extensions
----------------------------------------
- clang does not support the gcc extension that allows variable-length
arrays in structures. This is for a few reasons: one, it is tricky to
implement, two, the extension is completely undocumented, and three,
the extension appears to be rarely used. Note that clang *does*
support flexible array members (arrays with a zero or unspecified
size at the end of a structure).
- clang does not have an equivalent to gcc's "fold"; this means that
clang doesn't accept some constructs gcc might accept in contexts
where a constant expression is required, like "x-x" where x is a
variable.
- clang does not support ``__builtin_apply`` and friends; this extension
is extremely obscure and difficult to implement reliably.
.. _c_ms:
Microsoft extensions
--------------------
clang has support for many extensions from Microsoft Visual C++. To enable these
extensions, use the ``-fms-extensions`` command-line option. This is the default
for Windows targets. Clang does not implement every pragma or declspec provided
by MSVC, but the popular ones, such as ``__declspec(dllexport)`` and ``#pragma
comment(lib)`` are well supported.
clang has a ``-fms-compatibility`` flag that makes clang accept enough
invalid C++ to be able to parse most Microsoft headers. For example, it
allows `unqualified lookup of dependent base class members
`_, which is
a common compatibility issue with clang. This flag is enabled by default
for Windows targets.
``-fdelayed-template-parsing`` lets clang delay parsing of function template
definitions until the end of a translation unit. This flag is enabled by
default for Windows targets.
For compatibility with existing code that compiles with MSVC, clang defines the
``_MSC_VER`` and ``_MSC_FULL_VER`` macros. These default to the values of 1800
and 180000000 respectively, making clang look like an early release of Visual
C++ 2013. The ``-fms-compatibility-version=`` flag overrides these values. It
accepts a dotted version tuple, such as 19.00.23506. Changing the MSVC
compatibility version makes clang behave more like that version of MSVC. For
example, ``-fms-compatibility-version=19`` will enable C++14 features and define
``char16_t`` and ``char32_t`` as builtin types.
.. _cxx:
C++ Language Features
=====================
clang fully implements all of standard C++98 except for exported
templates (which were removed in C++11), and all of standard C++11
and the current draft standard for C++1y.
Controlling implementation limits
---------------------------------
.. option:: -fbracket-depth=N
Sets the limit for nested parentheses, brackets, and braces to N. The
default is 256.
.. option:: -fconstexpr-depth=N
Sets the limit for recursive constexpr function invocations to N. The
default is 512.
.. option:: -fconstexpr-steps=N
Sets the limit for the number of full-expressions evaluated in a single
constant expression evaluation. The default is 1048576.
.. option:: -ftemplate-depth=N
Sets the limit for recursively nested template instantiations to N. The
default is 1024.
.. option:: -foperator-arrow-depth=N
Sets the limit for iterative calls to 'operator->' functions to N. The
default is 256.
.. _objc:
Objective-C Language Features
=============================
.. _objcxx:
Objective-C++ Language Features
===============================
.. _openmp:
OpenMP Features
===============
Clang supports all OpenMP 4.5 directives and clauses. See :doc:`OpenMPSupport`
for additional details.
Use `-fopenmp` to enable OpenMP. Support for OpenMP can be disabled with
`-fno-openmp`.
Use `-fopenmp-simd` to enable OpenMP simd features only, without linking
the runtime library; for combined constructs
(e.g. ``#pragma omp parallel for simd``) the non-simd directives and clauses
will be ignored. This can be disabled with `-fno-openmp-simd`.
Controlling implementation limits
---------------------------------
.. option:: -fopenmp-use-tls
Controls code generation for OpenMP threadprivate variables. In presence of
this option all threadprivate variables are generated the same way as thread
local variables, using TLS support. If `-fno-openmp-use-tls`
is provided or target does not support TLS, code generation for threadprivate
variables relies on OpenMP runtime library.
.. _opencl:
OpenCL Features
===============
Clang can be used to compile OpenCL kernels for execution on a device
(e.g. GPU). It is possible to compile the kernel into a binary (e.g. for AMD or
Nvidia targets) that can be uploaded to run directly on a device (e.g. using
`clCreateProgramWithBinary
`_) or
into generic bitcode files loadable into other toolchains.
Compiling to a binary using the default target from the installation can be done
as follows:
.. code-block:: console
$ echo "kernel void k(){}" > test.cl
$ clang test.cl
Compiling for a specific target can be done by specifying the triple corresponding
to the target, for example:
.. code-block:: console
$ clang -target nvptx64-unknown-unknown test.cl
$ clang -target amdgcn-amd-amdhsa -mcpu=gfx900 test.cl
Compiling to bitcode can be done as follows:
.. code-block:: console
$ clang -c -emit-llvm test.cl
This will produce a generic test.bc file that can be used in vendor toolchains
to perform machine code generation.
Clang currently supports OpenCL C language standards up to v2.0.
OpenCL Specific Options
-----------------------
Most of the OpenCL build options from `the specification v2.0 section 5.8.4
`_ are available.
Examples:
.. code-block:: console
$ clang -cl-std=CL2.0 -cl-single-precision-constant test.cl
Some extra options are available to support special OpenCL features.
.. option:: -finclude-default-header
Loads standard includes during compilations. By default OpenCL headers are not
loaded and therefore standard library includes are not available. To load them
automatically a flag has been added to the frontend (see also :ref:`the section
on the OpenCL Header `):
.. code-block:: console
$ clang -Xclang -finclude-default-header test.cl
Alternatively ``-include`` or ``-I`` followed by the path to the header location
can be given manually.
.. code-block:: console
$ clang -I/lib/Headers/opencl-c.h test.cl
In this case the kernel code should contain ``#include `` just as a
regular C include.
.. _opencl_cl_ext:
.. option:: -cl-ext
Disables support of OpenCL extensions. All OpenCL targets provide a list
of extensions that they support. Clang allows to amend this using the ``-cl-ext``
flag with a comma-separated list of extensions prefixed with ``'+'`` or ``'-'``.
The syntax: ``-cl-ext=<(['-'|'+'][,])+>``, where extensions
can be either one of `the OpenCL specification extensions
`_
or any known vendor extension. Alternatively, ``'all'`` can be used to enable
or disable all known extensions.
Example disabling double support for the 64-bit SPIR target:
.. code-block:: console
$ clang -cc1 -triple spir64-unknown-unknown -cl-ext=-cl_khr_fp64 test.cl
Enabling all extensions except double support in R600 AMD GPU can be done using:
.. code-block:: console
$ clang -cc1 -triple r600-unknown-unknown -cl-ext=-all,+cl_khr_fp16 test.cl
.. _opencl_fake_address_space_map:
.. option:: -ffake-address-space-map
Overrides the target address space map with a fake map.
This allows adding explicit address space IDs to the bitcode for non-segmented
memory architectures that don't have separate IDs for each of the OpenCL
logical address spaces by default. Passing ``-ffake-address-space-map`` will
add/override address spaces of the target compiled for with the following values:
``1-global``, ``2-constant``, ``3-local``, ``4-generic``. The private address
space is represented by the absence of an address space attribute in the IR (see
also :ref:`the section on the address space attribute `).
.. code-block:: console
$ clang -ffake-address-space-map test.cl
Some other flags used for the compilation for C can also be passed while
compiling for OpenCL, examples: ``-c``, ``-O<1-4|s>``, ``-o``, ``-emit-llvm``, etc.
OpenCL Targets
--------------
OpenCL targets are derived from the regular Clang target classes. The OpenCL
specific parts of the target representation provide address space mapping as
well as a set of supported extensions.
Specific Targets
^^^^^^^^^^^^^^^^
There is a set of concrete HW architectures that OpenCL can be compiled for.
- For AMD target:
.. code-block:: console
$ clang -target amdgcn-amd-amdhsa -mcpu=gfx900 test.cl
- For Nvidia architectures:
.. code-block:: console
$ clang -target nvptx64-unknown-unknown test.cl
Generic Targets
^^^^^^^^^^^^^^^
- SPIR is available as a generic target to allow portable bitcode to be produced
that can be used across GPU toolchains. The implementation follows `the SPIR
specification `_. There are two flavors
available for 32 and 64 bits.
.. code-block:: console
$ clang -target spir-unknown-unknown test.cl
$ clang -target spir64-unknown-unknown test.cl
All known OpenCL extensions are supported in the SPIR targets. Clang will
generate SPIR v1.2 compatible IR for OpenCL versions up to 2.0 and SPIR v2.0
for OpenCL v2.0.
- x86 is used by some implementations that are x86 compatible and currently
remains for backwards compatibility (with older implementations prior to
SPIR target support). For "non-SPMD" targets which cannot spawn multiple
work-items on the fly using hardware, which covers practically all non-GPU
devices such as CPUs and DSPs, additional processing is needed for the kernels
to support multiple work-item execution. For this, a 3rd party toolchain,
such as for example `POCL `_, can be used.
This target does not support multiple memory segments and, therefore, the fake
address space map can be added using the :ref:`-ffake-address-space-map
` flag.
.. _opencl_header:
OpenCL Header
-------------
By default Clang will not include standard headers and therefore OpenCL builtin
functions and some types (i.e. vectors) are unknown. The default CL header is,
however, provided in the Clang installation and can be enabled by passing the
``-finclude-default-header`` flag to the Clang frontend.
.. code-block:: console
$ echo "bool is_wg_uniform(int i){return get_enqueued_local_size(i)==get_local_size(i);}" > test.cl
$ clang -Xclang -finclude-default-header -cl-std=CL2.0 test.cl
Because the header is very large and long to parse, PCH (:doc:`PCHInternals`)
and modules (:doc:`Modules`) are used internally to improve the compilation
speed.
To enable modules for OpenCL:
.. code-block:: console
$ clang -target spir-unknown-unknown -c -emit-llvm -Xclang -finclude-default-header -fmodules -fimplicit-module-maps -fmodules-cache-path= test.cl
OpenCL Extensions
-----------------
All of the ``cl_khr_*`` extensions from `the official OpenCL specification
`_
up to and including version 2.0 are available and set per target depending on the
support available in the specific architecture.
It is possible to alter the default extensions setting per target using
``-cl-ext`` flag. (See :ref:`flags description ` for more details).
Vendor extensions can be added flexibly by declaring the list of types and
functions associated with each extensions enclosed within the following
compiler pragma directives:
.. code-block:: c
#pragma OPENCL EXTENSION the_new_extension_name : begin
// declare types and functions associated with the extension here
#pragma OPENCL EXTENSION the_new_extension_name : end
For example, parsing the following code adds ``my_t`` type and ``my_func``
function to the custom ``my_ext`` extension.
.. code-block:: c
#pragma OPENCL EXTENSION my_ext : begin
typedef struct{
int a;
}my_t;
void my_func(my_t);
#pragma OPENCL EXTENSION my_ext : end
Declaring the same types in different vendor extensions is disallowed.
OpenCL Metadata
---------------
Clang uses metadata to provide additional OpenCL semantics in IR needed for
backends and OpenCL runtime.
Each kernel will have function metadata attached to it, specifying the arguments.
Kernel argument metadata is used to provide source level information for querying
at runtime, for example using the `clGetKernelArgInfo
`_
call.
Note that ``-cl-kernel-arg-info`` enables more information about the original CL
code to be added e.g. kernel parameter names will appear in the OpenCL metadata
along with other information.
The IDs used to encode the OpenCL's logical address spaces in the argument info
metadata follows the SPIR address space mapping as defined in the SPIR
specification `section 2.2
`_
OpenCL-Specific Attributes
--------------------------
OpenCL support in Clang contains a set of attribute taken directly from the
specification as well as additional attributes.
See also :doc:`AttributeReference`.
nosvm
^^^^^
Clang supports this attribute to comply to OpenCL v2.0 conformance, but it
does not have any effect on the IR. For more details reffer to the specification
`section 6.7.2
`_
opencl_unroll_hint
^^^^^^^^^^^^^^^^^^
The implementation of this feature mirrors the unroll hint for C.
More details on the syntax can be found in the specification
`section 6.11.5
`_
convergent
^^^^^^^^^^
To make sure no invalid optimizations occur for single program multiple data
(SPMD) / single instruction multiple thread (SIMT) Clang provides attributes that
can be used for special functions that have cross work item semantics.
An example is the subgroup operations such as `intel_sub_group_shuffle
`_
.. code-block:: c
// Define custom my_sub_group_shuffle(data, c)
// that makes use of intel_sub_group_shuffle
r1 = ...
if (r0) r1 = computeA();
// Shuffle data from r1 into r3
// of threads id r2.
r3 = my_sub_group_shuffle(r1, r2);
if (r0) r3 = computeB();
with non-SPMD semantics this is optimized to the following equivalent code:
.. code-block:: c
r1 = ...
if (!r0)
// Incorrect functionality! The data in r1
// have not been computed by all threads yet.
r3 = my_sub_group_shuffle(r1, r2);
else {
r1 = computeA();
r3 = my_sub_group_shuffle(r1, r2);
r3 = computeB();
}
Declaring the function ``my_sub_group_shuffle`` with the convergent attribute
would prevent this:
.. code-block:: c
my_sub_group_shuffle() __attribute__((convergent));
Using ``convergent`` guarantees correct execution by keeping CFG equivalence
wrt operations marked as ``convergent``. CFG ``G´`` is equivalent to ``G`` wrt
node ``Ni`` : ``iff ∀ Nj (i≠j)`` domination and post-domination relations with
respect to ``Ni`` remain the same in both ``G`` and ``G´``.
noduplicate
^^^^^^^^^^^
``noduplicate`` is more restrictive with respect to optimizations than
``convergent`` because a convergent function only preserves CFG equivalence.
This allows some optimizations to happen as long as the control flow remains
unmodified.
.. code-block:: c
for (int i=0; i<4; i++)
my_sub_group_shuffle()
can be modified to:
.. code-block:: c
my_sub_group_shuffle();
my_sub_group_shuffle();
my_sub_group_shuffle();
my_sub_group_shuffle();
while using ``noduplicate`` would disallow this. Also ``noduplicate`` doesn't
have the same safe semantics of CFG as ``convergent`` and can cause changes in
CFG that modify semantics of the original program.
``noduplicate`` is kept for backwards compatibility only and it considered to be
deprecated for future uses.
.. _opencl_addrsp:
address_space
^^^^^^^^^^^^^
Clang has arbitrary address space support using the ``address_space(N)``
attribute, where ``N`` is an integer number in the range ``0`` to ``16777215``
(``0xffffffu``).
An OpenCL implementation provides a list of standard address spaces using
keywords: ``private``, ``local``, ``global``, and ``generic``. In the AST and
in the IR local, global, or generic will be represented by the address space
attribute with the corresponding unique number. Note that private does not have
any corresponding attribute added and, therefore, is represented by the absence
of an address space number. The specific IDs for an address space do not have to
match between the AST and the IR. Typically in the AST address space numbers
represent logical segments while in the IR they represent physical segments.
Therefore, machines with flat memory segments can map all AST address space
numbers to the same physical segment ID or skip address space attribute
completely while generating the IR. However, if the address space information
is needed by the IR passes e.g. to improve alias analysis, it is recommended
to keep it and only lower to reflect physical memory segments in the late
machine passes.
OpenCL builtins
---------------
There are some standard OpenCL functions that are implemented as Clang builtins:
- All pipe functions from `section 6.13.16.2/6.13.16.3
`_ of
the OpenCL v2.0 kernel language specification. `
- Address space qualifier conversion functions ``to_global``/``to_local``/``to_private``
from `section 6.13.9
`_.
- All the ``enqueue_kernel`` functions from `section 6.13.17.1
`_ and
enqueue query functions from `section 6.13.17.5
`_.
.. _target_features:
Target-Specific Features and Limitations
========================================
CPU Architectures Features and Limitations
------------------------------------------
X86
^^^
The support for X86 (both 32-bit and 64-bit) is considered stable on
Darwin (Mac OS X), Linux, FreeBSD, and Dragonfly BSD: it has been tested
to correctly compile many large C, C++, Objective-C, and Objective-C++
codebases.
On ``x86_64-mingw32``, passing i128(by value) is incompatible with the
Microsoft x64 calling convention. You might need to tweak
``WinX86_64ABIInfo::classify()`` in lib/CodeGen/TargetInfo.cpp.
For the X86 target, clang supports the `-m16` command line
argument which enables 16-bit code output. This is broadly similar to
using ``asm(".code16gcc")`` with the GNU toolchain. The generated code
and the ABI remains 32-bit but the assembler emits instructions
appropriate for a CPU running in 16-bit mode, with address-size and
operand-size prefixes to enable 32-bit addressing and operations.
ARM
^^^
The support for ARM (specifically ARMv6 and ARMv7) is considered stable
on Darwin (iOS): it has been tested to correctly compile many large C,
C++, Objective-C, and Objective-C++ codebases. Clang only supports a
limited number of ARM architectures. It does not yet fully support
ARMv5, for example.
PowerPC
^^^^^^^
The support for PowerPC (especially PowerPC64) is considered stable
on Linux and FreeBSD: it has been tested to correctly compile many
large C and C++ codebases. PowerPC (32bit) is still missing certain
features (e.g. PIC code on ELF platforms).
Other platforms
^^^^^^^^^^^^^^^
clang currently contains some support for other architectures (e.g. Sparc);
however, significant pieces of code generation are still missing, and they
haven't undergone significant testing.
clang contains limited support for the MSP430 embedded processor, but
both the clang support and the LLVM backend support are highly
experimental.
Other platforms are completely unsupported at the moment. Adding the
minimal support needed for parsing and semantic analysis on a new
platform is quite easy; see ``lib/Basic/Targets.cpp`` in the clang source
tree. This level of support is also sufficient for conversion to LLVM IR
for simple programs. Proper support for conversion to LLVM IR requires
adding code to ``lib/CodeGen/CGCall.cpp`` at the moment; this is likely to
change soon, though. Generating assembly requires a suitable LLVM
backend.
Operating System Features and Limitations
-----------------------------------------
Darwin (Mac OS X)
^^^^^^^^^^^^^^^^^
Thread Sanitizer is not supported.
Windows
^^^^^^^
Clang has experimental support for targeting "Cygming" (Cygwin / MinGW)
platforms.
See also :ref:`Microsoft Extensions `.
Cygwin
""""""
Clang works on Cygwin-1.7.
MinGW32
"""""""
Clang works on some mingw32 distributions. Clang assumes directories as
below;
- ``C:/mingw/include``
- ``C:/mingw/lib``
- ``C:/mingw/lib/gcc/mingw32/4.[3-5].0/include/c++``
On MSYS, a few tests might fail.
MinGW-w64
"""""""""
For 32-bit (i686-w64-mingw32), and 64-bit (x86\_64-w64-mingw32), Clang
assumes as below;
- ``GCC versions 4.5.0 to 4.5.3, 4.6.0 to 4.6.2, or 4.7.0 (for the C++ header search path)``
- ``some_directory/bin/gcc.exe``
- ``some_directory/bin/clang.exe``
- ``some_directory/bin/clang++.exe``
- ``some_directory/bin/../include/c++/GCC_version``
- ``some_directory/bin/../include/c++/GCC_version/x86_64-w64-mingw32``
- ``some_directory/bin/../include/c++/GCC_version/i686-w64-mingw32``
- ``some_directory/bin/../include/c++/GCC_version/backward``
- ``some_directory/bin/../x86_64-w64-mingw32/include``
- ``some_directory/bin/../i686-w64-mingw32/include``
- ``some_directory/bin/../include``
This directory layout is standard for any toolchain you will find on the
official `MinGW-w64 website `_.
Clang expects the GCC executable "gcc.exe" compiled for
``i686-w64-mingw32`` (or ``x86_64-w64-mingw32``) to be present on PATH.
`Some tests might fail `_ on
``x86_64-w64-mingw32``.
.. _clang-cl:
clang-cl
========
clang-cl is an alternative command-line interface to Clang, designed for
compatibility with the Visual C++ compiler, cl.exe.
To enable clang-cl to find system headers, libraries, and the linker when run
from the command-line, it should be executed inside a Visual Studio Native Tools
Command Prompt or a regular Command Prompt where the environment has been set
up using e.g. `vcvarsall.bat `_.
clang-cl can also be used from inside Visual Studio by selecting the LLVM
Platform Toolset. The toolset is not part of the installer, but may be installed
separately from the
`Visual Studio Marketplace `_.
To use the toolset, select a project in Solution Explorer, open its Property
Page (Alt+F7), and in the "General" section of "Configuration Properties"
change "Platform Toolset" to LLVM. Doing so enables an additional Property
Page for selecting the clang-cl executable to use for builds.
To use the toolset with MSBuild directly, invoke it with e.g.
``/p:PlatformToolset=LLVM``. This allows trying out the clang-cl toolchain
without modifying your project files.
It's also possible to point MSBuild at clang-cl without changing toolset by
passing ``/p:CLToolPath=c:\llvm\bin /p:CLToolExe=clang-cl.exe``.
When using CMake and the Visual Studio generators, the toolset can be set with the ``-T`` flag:
::
cmake -G"Visual Studio 15 2017" -T LLVM ..
When using CMake with the Ninja generator, set the ``CMAKE_C_COMPILER`` and
``CMAKE_CXX_COMPILER`` variables to clang-cl:
::
cmake -GNinja -DCMAKE_C_COMPILER="c:/Program Files (x86)/LLVM/bin/clang-cl.exe"
-DCMAKE_CXX_COMPILER="c:/Program Files (x86)/LLVM/bin/clang-cl.exe" ..
Command-Line Options
--------------------
To be compatible with cl.exe, clang-cl supports most of the same command-line
options. Those options can start with either ``/`` or ``-``. It also supports
some of Clang's core options, such as the ``-W`` options.
Options that are known to clang-cl, but not currently supported, are ignored
with a warning. For example:
::
clang-cl.exe: warning: argument unused during compilation: '/AI'
To suppress warnings about unused arguments, use the ``-Qunused-arguments`` option.
Options that are not known to clang-cl will be ignored by default. Use the
``-Werror=unknown-argument`` option in order to treat them as errors. If these
options are spelled with a leading ``/``, they will be mistaken for a filename:
::
clang-cl.exe: error: no such file or directory: '/foobar'
Please `file a bug `_
for any valid cl.exe flags that clang-cl does not understand.
Execute ``clang-cl /?`` to see a list of supported options:
::
CL.EXE COMPATIBILITY OPTIONS:
/? Display available options
/arch: Set architecture for code generation
/Brepro- Emit an object file which cannot be reproduced over time
/Brepro Emit an object file which can be reproduced over time
/clang: Pass to the clang driver
/C Don't discard comments when preprocessing
/c Compile only
/d1PP Retain macro definitions in /E mode
/d1reportAllClassLayout Dump record layout information
/diagnostics:caret Enable caret and column diagnostics (on by default)
/diagnostics:classic Disable column and caret diagnostics
/diagnostics:column Disable caret diagnostics but keep column info
/D Define macro
/EH Exception handling model
/EP Disable linemarker output and preprocess to stdout
/execution-charset:
Runtime encoding, supports only UTF-8
/E Preprocess to stdout
/fallback Fall back to cl.exe if clang-cl fails to compile
/FA Output assembly code file during compilation
/Fa Output assembly code to this file during compilation (with /FA)
/Fe Set output executable file or directory (ends in / or \)
/FI Include file before parsing
/Fi Set preprocess output file name (with /P)
/Fo Set output object file, or directory (ends in / or \) (with /c)
/fp:except-
/fp:except
/fp:fast
/fp:precise
/fp:strict
/Fp Set pch filename (with /Yc and /Yu)
/GA Assume thread-local variables are defined in the executable
/Gd Set __cdecl as a default calling convention
/GF- Disable string pooling
/GF Enable string pooling (default)
/GR- Disable emission of RTTI data
/Gregcall Set __regcall as a default calling convention
/GR Enable emission of RTTI data
/Gr Set __fastcall as a default calling convention
/GS- Disable buffer security check
/GS Enable buffer security check (default)
/Gs Use stack probes (default)
/Gs Set stack probe size (default 4096)
/guard: Enable Control Flow Guard with /guard:cf,
or only the table with /guard:cf,nochecks
/Gv Set __vectorcall as a default calling convention
/Gw- Don't put each data item in its own section
/Gw Put each data item in its own section
/GX- Disable exception handling
/GX Enable exception handling
/Gy- Don't put each function in its own section (default)
/Gy Put each function in its own section
/Gz Set __stdcall as a default calling convention
/help Display available options
/imsvc Add directory to system include search path, as if part of %INCLUDE%
/I Add directory to include search path
/J Make char type unsigned
/LDd Create debug DLL
/LD Create DLL
/link Forward options to the linker
/MDd Use DLL debug run-time
/MD Use DLL run-time
/MTd Use static debug run-time
/MT Use static run-time
/O0 Disable optimization
/O1 Optimize for size (same as /Og /Os /Oy /Ob2 /GF /Gy)
/O2 Optimize for speed (same as /Og /Oi /Ot /Oy /Ob2 /GF /Gy)
/Ob0 Disable function inlining
/Ob1 Only inline functions which are (explicitly or implicitly) marked inline
/Ob2 Inline functions as deemed beneficial by the compiler
/Od Disable optimization
/Og No effect
/Oi- Disable use of builtin functions
/Oi Enable use of builtin functions
/Os Optimize for size
/Ot Optimize for speed
/Ox Deprecated (same as /Og /Oi /Ot /Oy /Ob2); use /O2 instead
/Oy- Disable frame pointer omission (x86 only, default)
/Oy Enable frame pointer omission (x86 only)
/O Set multiple /O flags at once; e.g. '/O2y-' for '/O2 /Oy-'
/o Set output file or directory (ends in / or \)
/P Preprocess to file
/Qvec- Disable the loop vectorization passes
/Qvec Enable the loop vectorization passes
/showFilenames- Don't print the name of each compiled file (default)
/showFilenames Print the name of each compiled file
/showIncludes Print info about included files to stderr
/source-charset: Source encoding, supports only UTF-8
/std: Language standard to compile for
/TC Treat all source files as C
/Tc Specify a C source file
/TP Treat all source files as C++
/Tp Specify a C++ source file
/utf-8 Set source and runtime encoding to UTF-8 (default)
/U Undefine macro
/vd Control vtordisp placement
/vmb Use a best-case representation method for member pointers
/vmg Use a most-general representation for member pointers
/vmm Set the default most-general representation to multiple inheritance
/vms Set the default most-general representation to single inheritance
/vmv Set the default most-general representation to virtual inheritance
/volatile:iso Volatile loads and stores have standard semantics
/volatile:ms Volatile loads and stores have acquire and release semantics
/W0 Disable all warnings
/W1 Enable -Wall
/W2 Enable -Wall
/W3 Enable -Wall
/W4 Enable -Wall and -Wextra
/Wall Enable -Weverything
/WX- Do not treat warnings as errors
/WX Treat warnings as errors
/w Disable all warnings
/X Don't add %INCLUDE% to the include search path
/Y- Disable precompiled headers, overrides /Yc and /Yu
/Yc Generate a pch file for all code up to and including
/Yu Load a pch file and use it instead of all code up to and including
/Z7 Enable CodeView debug information in object files
/Zc:dllexportInlines- Don't dllexport/dllimport inline member functions of dllexport/import classes
/Zc:dllexportInlines dllexport/dllimport inline member functions of dllexport/import classes (default)
/Zc:sizedDealloc- Disable C++14 sized global deallocation functions
/Zc:sizedDealloc Enable C++14 sized global deallocation functions
/Zc:strictStrings Treat string literals as const
/Zc:threadSafeInit- Disable thread-safe initialization of static variables
/Zc:threadSafeInit Enable thread-safe initialization of static variables
/Zc:trigraphs- Disable trigraphs (default)
/Zc:trigraphs Enable trigraphs
/Zc:twoPhase- Disable two-phase name lookup in templates
/Zc:twoPhase Enable two-phase name lookup in templates
/Zd Emit debug line number tables only
/Zi Alias for /Z7. Does not produce PDBs.
/Zl Don't mention any default libraries in the object file
/Zp Set the default maximum struct packing alignment to 1
/Zp Specify the default maximum struct packing alignment
/Zs Syntax-check only
OPTIONS:
-### Print (but do not run) the commands to run for this compilation
--analyze Run the static analyzer
-faddrsig Emit an address-significance table
-fansi-escape-codes Use ANSI escape codes for diagnostics
-fblocks Enable the 'blocks' language feature
-fcf-protection= Instrument control-flow architecture protection. Options: return, branch, full, none.
-fcf-protection Enable cf-protection in 'full' mode
-fcolor-diagnostics Use colors in diagnostics
-fcomplete-member-pointers
Require member pointer base types to be complete if they would be significant under the Microsoft ABI
-fcoverage-mapping Generate coverage mapping to enable code coverage analysis
-fdebug-macro Emit macro debug information
-fdelayed-template-parsing
Parse templated function definitions at the end of the translation unit
-fdiagnostics-absolute-paths
Print absolute paths in diagnostics
-fdiagnostics-parseable-fixits
Print fix-its in machine parseable form
-flto= Set LTO mode to either 'full' or 'thin'
-flto Enable LTO in 'full' mode
-fmerge-all-constants Allow merging of constants
-fms-compatibility-version=
Dot-separated value representing the Microsoft compiler version
number to report in _MSC_VER (0 = don't define it (default))
-fms-compatibility Enable full Microsoft Visual C++ compatibility
-fms-extensions Accept some non-standard constructs supported by the Microsoft compiler
-fmsc-version= Microsoft compiler version number to report in _MSC_VER
(0 = don't define it (default))
-fno-addrsig Don't emit an address-significance table
-fno-builtin- Disable implicit builtin knowledge of a specific function
-fno-builtin Disable implicit builtin knowledge of functions
-fno-complete-member-pointers
Do not require member pointer base types to be complete if they would be significant under the Microsoft ABI
-fno-coverage-mapping Disable code coverage analysis
-fno-crash-diagnostics Disable auto-generation of preprocessed source files and a script for reproduction during a clang crash
-fno-debug-macro Do not emit macro debug information
-fno-delayed-template-parsing
Disable delayed template parsing
-fno-sanitize-address-poison-custom-array-cookie
Disable poisoning array cookies when using custom operator new[] in AddressSanitizer
-fno-sanitize-address-use-after-scope
Disable use-after-scope detection in AddressSanitizer
-fno-sanitize-address-use-odr-indicator
Disable ODR indicator globals
-fno-sanitize-blacklist Don't use blacklist file for sanitizers
-fno-sanitize-cfi-cross-dso
Disable control flow integrity (CFI) checks for cross-DSO calls.
-fno-sanitize-coverage=
Disable specified features of coverage instrumentation for Sanitizers
-fno-sanitize-memory-track-origins
Disable origins tracking in MemorySanitizer
-fno-sanitize-memory-use-after-dtor
Disable use-after-destroy detection in MemorySanitizer
-fno-sanitize-recover=
Disable recovery for specified sanitizers
-fno-sanitize-stats Disable sanitizer statistics gathering.
-fno-sanitize-thread-atomics
Disable atomic operations instrumentation in ThreadSanitizer
-fno-sanitize-thread-func-entry-exit
Disable function entry/exit instrumentation in ThreadSanitizer
-fno-sanitize-thread-memory-access
Disable memory access instrumentation in ThreadSanitizer
-fno-sanitize-trap=
Disable trapping for specified sanitizers
-fno-standalone-debug Limit debug information produced to reduce size of debug binary
-fobjc-runtime= Specify the target Objective-C runtime kind and version
-fprofile-exclude-files=
Instrument only functions from files where names don't match all the regexes separated by a semi-colon
-fprofile-filter-files=
Instrument only functions from files where names match any regex separated by a semi-colon
-fprofile-instr-generate=
Generate instrumented code to collect execution counts into
(overridden by LLVM_PROFILE_FILE env var)
-fprofile-instr-generate
Generate instrumented code to collect execution counts into default.profraw file
(overridden by '=' form of option or LLVM_PROFILE_FILE env var)
-fprofile-instr-use=
Use instrumentation data for profile-guided optimization
-fprofile-remapping-file=
Use the remappings described in to match the profile data against names in the program
-fsanitize-address-field-padding=
Level of field padding for AddressSanitizer
-fsanitize-address-globals-dead-stripping
Enable linker dead stripping of globals in AddressSanitizer
-fsanitize-address-poison-custom-array-cookie
Enable poisoning array cookies when using custom operator new[] in AddressSanitizer
-fsanitize-address-use-after-scope
Enable use-after-scope detection in AddressSanitizer
-fsanitize-address-use-odr-indicator
Enable ODR indicator globals to avoid false ODR violation reports in partially sanitized programs at the cost of an increase in binary size
-fsanitize-blacklist=
Path to blacklist file for sanitizers
-fsanitize-cfi-cross-dso
Enable control flow integrity (CFI) checks for cross-DSO calls.
-fsanitize-cfi-icall-generalize-pointers
Generalize pointers in CFI indirect call type signature checks
-fsanitize-coverage=
Specify the type of coverage instrumentation for Sanitizers
-fsanitize-hwaddress-abi=
Select the HWAddressSanitizer ABI to target (interceptor or platform, default interceptor)
-fsanitize-memory-track-origins=
Enable origins tracking in MemorySanitizer
-fsanitize-memory-track-origins
Enable origins tracking in MemorySanitizer
-fsanitize-memory-use-after-dtor
Enable use-after-destroy detection in MemorySanitizer
-fsanitize-recover=
Enable recovery for specified sanitizers
-fsanitize-stats Enable sanitizer statistics gathering.
-fsanitize-thread-atomics
Enable atomic operations instrumentation in ThreadSanitizer (default)
-fsanitize-thread-func-entry-exit
Enable function entry/exit instrumentation in ThreadSanitizer (default)
-fsanitize-thread-memory-access
Enable memory access instrumentation in ThreadSanitizer (default)
-fsanitize-trap= Enable trapping for specified sanitizers
-fsanitize-undefined-strip-path-components=
Strip (or keep only, if negative) a given number of path components when emitting check metadata.
-fsanitize= Turn on runtime checks for various forms of undefined or suspicious
behavior. See user manual for available checks
-fsplit-lto-unit Enables splitting of the LTO unit.
-fstandalone-debug Emit full debug info for all types used by the program
-fwhole-program-vtables Enables whole-program vtable optimization. Requires -flto
-gcodeview-ghash Emit type record hashes in a .debug$H section
-gcodeview Generate CodeView debug information
-gline-directives-only Emit debug line info directives only
-gline-tables-only Emit debug line number tables only
-miamcu Use Intel MCU ABI
-mllvm Additional arguments to forward to LLVM's option processing
-nobuiltininc Disable builtin #include directories
-Qunused-arguments Don't emit warning for unused driver arguments
-R Enable the specified remark
--target= Generate code for the given target
--version Print version information
-v Show commands to run and use verbose output
-W Enable the specified warning
-Xclang Pass to the clang compiler
The /clang: Option
^^^^^^^^^^^^^^^^^^
When clang-cl is run with a set of ``/clang:`` options, it will gather all
of the ```` arguments and process them as if they were passed to the clang
driver. This mechanism allows you to pass flags that are not exposed in the
clang-cl options or flags that have a different meaning when passed to the clang
driver. Regardless of where they appear in the command line, the ``/clang:``
arguments are treated as if they were passed at the end of the clang-cl command
line.
The /Zc:dllexportInlines- Option
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This causes the class-level `dllexport` and `dllimport` attributes to not apply
to inline member functions, as they otherwise would. For example, in the code
below `S::foo()` would normally be defined and exported by the DLL, but when
using the ``/Zc:dllexportInlines-`` flag it is not:
.. code-block:: c
struct __declspec(dllexport) S {
void foo() {}
}
This has the benefit that the compiler doesn't need to emit a definition of
`S::foo()` in every translation unit where the declaration is included, as it
would otherwise do to ensure there's a definition in the DLL even if it's not
used there. If the declaration occurs in a header file that's widely used, this
can save significant compilation time and output size. It also reduces the
number of functions exported by the DLL similarly to what
``-fvisibility-inlines-hidden`` does for shared objects on ELF and Mach-O.
Since the function declaration comes with an inline definition, users of the
library can use that definition directly instead of importing it from the DLL.
Note that the Microsoft Visual C++ compiler does not support this option, and
if code in a DLL is compiled with ``/Zc:dllexportInlines-``, the code using the
DLL must be compiled in the same way so that it doesn't attempt to dllimport
the inline member functions. The reverse scenario should generally work though:
a DLL compiled without this flag (such as a system library compiled with Visual
C++) can be referenced from code compiled using the flag, meaning that the
referencing code will use the inline definitions instead of importing them from
the DLL.
Also note that like when using ``-fvisibility-inlines-hidden``, the address of
`S::foo()` will be different inside and outside the DLL, breaking the C/C++
standard requirement that functions have a unique address.
The flag does not apply to explicit class template instantiation definitions or
declarations, as those are typically used to explicitly provide a single
definition in a DLL, (dllexported instantiation definition) or to signal that
the definition is available elsewhere (dllimport instantiation declaration). It
also doesn't apply to inline members with static local variables, to ensure
that the same instance of the variable is used inside and outside the DLL.
Using this flag can cause problems when inline functions that would otherwise
be dllexported refer to internal symbols of a DLL. For example:
.. code-block:: c
void internal();
struct __declspec(dllimport) S {
void foo() { internal(); }
}
Normally, references to `S::foo()` would use the definition in the DLL from
which it was exported, and which presumably also has the definition of
`internal()`. However, when using ``/Zc:dllexportInlines-``, the inline
definition of `S::foo()` is used directly, resulting in a link error since
`internal()` is not available. Even worse, if there is an inline definition of
`internal()` containing a static local variable, we will now refer to a
different instance of that variable than in the DLL:
.. code-block:: c
inline int internal() { static int x; return x++; }
struct __declspec(dllimport) S {
int foo() { return internal(); }
}
This could lead to very subtle bugs. Using ``-fvisibility-inlines-hidden`` can
lead to the same issue. To avoid it in this case, make `S::foo()` or
`internal()` non-inline, or mark them `dllimport/dllexport` explicitly.
The /fallback Option
^^^^^^^^^^^^^^^^^^^^
When clang-cl is run with the ``/fallback`` option, it will first try to
compile files itself. For any file that it fails to compile, it will fall back
and try to compile the file by invoking cl.exe.
This option is intended to be used as a temporary means to build projects where
clang-cl cannot successfully compile all the files. clang-cl may fail to compile
a file either because it cannot generate code for some C++ feature, or because
it cannot parse some Microsoft language extension.
Index: vendor/clang/dist-release_80/include/clang/AST/Expr.h
===================================================================
--- vendor/clang/dist-release_80/include/clang/AST/Expr.h (revision 344536)
+++ vendor/clang/dist-release_80/include/clang/AST/Expr.h (revision 344537)
@@ -1,5590 +1,5595 @@
//===--- Expr.h - Classes for representing expressions ----------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the Expr interface and subclasses.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_AST_EXPR_H
#define LLVM_CLANG_AST_EXPR_H
#include "clang/AST/APValue.h"
#include "clang/AST/ASTVector.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclAccessPair.h"
#include "clang/AST/OperationKinds.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/TemplateBase.h"
#include "clang/AST/Type.h"
#include "clang/Basic/CharInfo.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SyncScope.h"
#include "clang/Basic/TypeTraits.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/AtomicOrdering.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/TrailingObjects.h"
namespace clang {
class APValue;
class ASTContext;
class BlockDecl;
class CXXBaseSpecifier;
class CXXMemberCallExpr;
class CXXOperatorCallExpr;
class CastExpr;
class Decl;
class IdentifierInfo;
class MaterializeTemporaryExpr;
class NamedDecl;
class ObjCPropertyRefExpr;
class OpaqueValueExpr;
class ParmVarDecl;
class StringLiteral;
class TargetInfo;
class ValueDecl;
/// A simple array of base specifiers.
typedef SmallVector CXXCastPath;
/// An adjustment to be made to the temporary created when emitting a
/// reference binding, which accesses a particular subobject of that temporary.
struct SubobjectAdjustment {
enum {
DerivedToBaseAdjustment,
FieldAdjustment,
MemberPointerAdjustment
} Kind;
struct DTB {
const CastExpr *BasePath;
const CXXRecordDecl *DerivedClass;
};
struct P {
const MemberPointerType *MPT;
Expr *RHS;
};
union {
struct DTB DerivedToBase;
FieldDecl *Field;
struct P Ptr;
};
SubobjectAdjustment(const CastExpr *BasePath,
const CXXRecordDecl *DerivedClass)
: Kind(DerivedToBaseAdjustment) {
DerivedToBase.BasePath = BasePath;
DerivedToBase.DerivedClass = DerivedClass;
}
SubobjectAdjustment(FieldDecl *Field)
: Kind(FieldAdjustment) {
this->Field = Field;
}
SubobjectAdjustment(const MemberPointerType *MPT, Expr *RHS)
: Kind(MemberPointerAdjustment) {
this->Ptr.MPT = MPT;
this->Ptr.RHS = RHS;
}
};
/// This represents one expression. Note that Expr's are subclasses of Stmt.
/// This allows an expression to be transparently used any place a Stmt is
/// required.
class Expr : public Stmt {
QualType TR;
protected:
Expr(StmtClass SC, QualType T, ExprValueKind VK, ExprObjectKind OK,
bool TD, bool VD, bool ID, bool ContainsUnexpandedParameterPack)
: Stmt(SC)
{
ExprBits.TypeDependent = TD;
ExprBits.ValueDependent = VD;
ExprBits.InstantiationDependent = ID;
ExprBits.ValueKind = VK;
ExprBits.ObjectKind = OK;
assert(ExprBits.ObjectKind == OK && "truncated kind");
ExprBits.ContainsUnexpandedParameterPack = ContainsUnexpandedParameterPack;
setType(T);
}
/// Construct an empty expression.
explicit Expr(StmtClass SC, EmptyShell) : Stmt(SC) { }
public:
QualType getType() const { return TR; }
void setType(QualType t) {
// In C++, the type of an expression is always adjusted so that it
// will not have reference type (C++ [expr]p6). Use
// QualType::getNonReferenceType() to retrieve the non-reference
// type. Additionally, inspect Expr::isLvalue to determine whether
// an expression that is adjusted in this manner should be
// considered an lvalue.
assert((t.isNull() || !t->isReferenceType()) &&
"Expressions can't have reference type");
TR = t;
}
/// isValueDependent - Determines whether this expression is
/// value-dependent (C++ [temp.dep.constexpr]). For example, the
/// array bound of "Chars" in the following example is
/// value-dependent.
/// @code
/// template struct meta_string;
/// @endcode
bool isValueDependent() const { return ExprBits.ValueDependent; }
/// Set whether this expression is value-dependent or not.
void setValueDependent(bool VD) {
ExprBits.ValueDependent = VD;
}
/// isTypeDependent - Determines whether this expression is
/// type-dependent (C++ [temp.dep.expr]), which means that its type
/// could change from one template instantiation to the next. For
/// example, the expressions "x" and "x + y" are type-dependent in
/// the following code, but "y" is not type-dependent:
/// @code
/// template
/// void add(T x, int y) {
/// x + y;
/// }
/// @endcode
bool isTypeDependent() const { return ExprBits.TypeDependent; }
/// Set whether this expression is type-dependent or not.
void setTypeDependent(bool TD) {
ExprBits.TypeDependent = TD;
}
/// Whether this expression is instantiation-dependent, meaning that
/// it depends in some way on a template parameter, even if neither its type
/// nor (constant) value can change due to the template instantiation.
///
/// In the following example, the expression \c sizeof(sizeof(T() + T())) is
/// instantiation-dependent (since it involves a template parameter \c T), but
/// is neither type- nor value-dependent, since the type of the inner
/// \c sizeof is known (\c std::size_t) and therefore the size of the outer
/// \c sizeof is known.
///
/// \code
/// template
/// void f(T x, T y) {
/// sizeof(sizeof(T() + T());
/// }
/// \endcode
///
bool isInstantiationDependent() const {
return ExprBits.InstantiationDependent;
}
/// Set whether this expression is instantiation-dependent or not.
void setInstantiationDependent(bool ID) {
ExprBits.InstantiationDependent = ID;
}
/// Whether this expression contains an unexpanded parameter
/// pack (for C++11 variadic templates).
///
/// Given the following function template:
///
/// \code
/// template
/// void forward(const F &f, Types &&...args) {
/// f(static_cast(args)...);
/// }
/// \endcode
///
/// The expressions \c args and \c static_cast(args) both
/// contain parameter packs.
bool containsUnexpandedParameterPack() const {
return ExprBits.ContainsUnexpandedParameterPack;
}
/// Set the bit that describes whether this expression
/// contains an unexpanded parameter pack.
void setContainsUnexpandedParameterPack(bool PP = true) {
ExprBits.ContainsUnexpandedParameterPack = PP;
}
/// getExprLoc - Return the preferred location for the arrow when diagnosing
/// a problem with a generic expression.
SourceLocation getExprLoc() const LLVM_READONLY;
/// isUnusedResultAWarning - Return true if this immediate expression should
/// be warned about if the result is unused. If so, fill in expr, location,
/// and ranges with expr to warn on and source locations/ranges appropriate
/// for a warning.
bool isUnusedResultAWarning(const Expr *&WarnExpr, SourceLocation &Loc,
SourceRange &R1, SourceRange &R2,
ASTContext &Ctx) const;
/// isLValue - True if this expression is an "l-value" according to
/// the rules of the current language. C and C++ give somewhat
/// different rules for this concept, but in general, the result of
/// an l-value expression identifies a specific object whereas the
/// result of an r-value expression is a value detached from any
/// specific storage.
///
/// C++11 divides the concept of "r-value" into pure r-values
/// ("pr-values") and so-called expiring values ("x-values"), which
/// identify specific objects that can be safely cannibalized for
/// their resources. This is an unfortunate abuse of terminology on
/// the part of the C++ committee. In Clang, when we say "r-value",
/// we generally mean a pr-value.
bool isLValue() const { return getValueKind() == VK_LValue; }
bool isRValue() const { return getValueKind() == VK_RValue; }
bool isXValue() const { return getValueKind() == VK_XValue; }
bool isGLValue() const { return getValueKind() != VK_RValue; }
enum LValueClassification {
LV_Valid,
LV_NotObjectType,
LV_IncompleteVoidType,
LV_DuplicateVectorComponents,
LV_InvalidExpression,
LV_InvalidMessageExpression,
LV_MemberFunction,
LV_SubObjCPropertySetting,
LV_ClassTemporary,
LV_ArrayTemporary
};
/// Reasons why an expression might not be an l-value.
LValueClassification ClassifyLValue(ASTContext &Ctx) const;
enum isModifiableLvalueResult {
MLV_Valid,
MLV_NotObjectType,
MLV_IncompleteVoidType,
MLV_DuplicateVectorComponents,
MLV_InvalidExpression,
MLV_LValueCast, // Specialized form of MLV_InvalidExpression.
MLV_IncompleteType,
MLV_ConstQualified,
MLV_ConstQualifiedField,
MLV_ConstAddrSpace,
MLV_ArrayType,
MLV_NoSetterProperty,
MLV_MemberFunction,
MLV_SubObjCPropertySetting,
MLV_InvalidMessageExpression,
MLV_ClassTemporary,
MLV_ArrayTemporary
};
/// isModifiableLvalue - C99 6.3.2.1: an lvalue that does not have array type,
/// does not have an incomplete type, does not have a const-qualified type,
/// and if it is a structure or union, does not have any member (including,
/// recursively, any member or element of all contained aggregates or unions)
/// with a const-qualified type.
///
/// \param Loc [in,out] - A source location which *may* be filled
/// in with the location of the expression making this a
/// non-modifiable lvalue, if specified.
isModifiableLvalueResult
isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc = nullptr) const;
/// The return type of classify(). Represents the C++11 expression
/// taxonomy.
class Classification {
public:
/// The various classification results. Most of these mean prvalue.
enum Kinds {
CL_LValue,
CL_XValue,
CL_Function, // Functions cannot be lvalues in C.
CL_Void, // Void cannot be an lvalue in C.
CL_AddressableVoid, // Void expression whose address can be taken in C.
CL_DuplicateVectorComponents, // A vector shuffle with dupes.
CL_MemberFunction, // An expression referring to a member function
CL_SubObjCPropertySetting,
CL_ClassTemporary, // A temporary of class type, or subobject thereof.
CL_ArrayTemporary, // A temporary of array type.
CL_ObjCMessageRValue, // ObjC message is an rvalue
CL_PRValue // A prvalue for any other reason, of any other type
};
/// The results of modification testing.
enum ModifiableType {
CM_Untested, // testModifiable was false.
CM_Modifiable,
CM_RValue, // Not modifiable because it's an rvalue
CM_Function, // Not modifiable because it's a function; C++ only
CM_LValueCast, // Same as CM_RValue, but indicates GCC cast-as-lvalue ext
CM_NoSetterProperty,// Implicit assignment to ObjC property without setter
CM_ConstQualified,
CM_ConstQualifiedField,
CM_ConstAddrSpace,
CM_ArrayType,
CM_IncompleteType
};
private:
friend class Expr;
unsigned short Kind;
unsigned short Modifiable;
explicit Classification(Kinds k, ModifiableType m)
: Kind(k), Modifiable(m)
{}
public:
Classification() {}
Kinds getKind() const { return static_cast(Kind); }
ModifiableType getModifiable() const {
assert(Modifiable != CM_Untested && "Did not test for modifiability.");
return static_cast(Modifiable);
}
bool isLValue() const { return Kind == CL_LValue; }
bool isXValue() const { return Kind == CL_XValue; }
bool isGLValue() const { return Kind <= CL_XValue; }
bool isPRValue() const { return Kind >= CL_Function; }
bool isRValue() const { return Kind >= CL_XValue; }
bool isModifiable() const { return getModifiable() == CM_Modifiable; }
/// Create a simple, modifiably lvalue
static Classification makeSimpleLValue() {
return Classification(CL_LValue, CM_Modifiable);
}
};
/// Classify - Classify this expression according to the C++11
/// expression taxonomy.
///
/// C++11 defines ([basic.lval]) a new taxonomy of expressions to replace the
/// old lvalue vs rvalue. This function determines the type of expression this
/// is. There are three expression types:
/// - lvalues are classical lvalues as in C++03.
/// - prvalues are equivalent to rvalues in C++03.
/// - xvalues are expressions yielding unnamed rvalue references, e.g. a
/// function returning an rvalue reference.
/// lvalues and xvalues are collectively referred to as glvalues, while
/// prvalues and xvalues together form rvalues.
Classification Classify(ASTContext &Ctx) const {
return ClassifyImpl(Ctx, nullptr);
}
/// ClassifyModifiable - Classify this expression according to the
/// C++11 expression taxonomy, and see if it is valid on the left side
/// of an assignment.
///
/// This function extends classify in that it also tests whether the
/// expression is modifiable (C99 6.3.2.1p1).
/// \param Loc A source location that might be filled with a relevant location
/// if the expression is not modifiable.
Classification ClassifyModifiable(ASTContext &Ctx, SourceLocation &Loc) const{
return ClassifyImpl(Ctx, &Loc);
}
/// getValueKindForType - Given a formal return or parameter type,
/// give its value kind.
static ExprValueKind getValueKindForType(QualType T) {
if (const ReferenceType *RT = T->getAs())
return (isa(RT)
? VK_LValue
: (RT->getPointeeType()->isFunctionType()
? VK_LValue : VK_XValue));
return VK_RValue;
}
/// getValueKind - The value kind that this expression produces.
ExprValueKind getValueKind() const {
return static_cast(ExprBits.ValueKind);
}
/// getObjectKind - The object kind that this expression produces.
/// Object kinds are meaningful only for expressions that yield an
/// l-value or x-value.
ExprObjectKind getObjectKind() const {
return static_cast(ExprBits.ObjectKind);
}
bool isOrdinaryOrBitFieldObject() const {
ExprObjectKind OK = getObjectKind();
return (OK == OK_Ordinary || OK == OK_BitField);
}
/// setValueKind - Set the value kind produced by this expression.
void setValueKind(ExprValueKind Cat) { ExprBits.ValueKind = Cat; }
/// setObjectKind - Set the object kind produced by this expression.
void setObjectKind(ExprObjectKind Cat) { ExprBits.ObjectKind = Cat; }
private:
Classification ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const;
public:
/// Returns true if this expression is a gl-value that
/// potentially refers to a bit-field.
///
/// In C++, whether a gl-value refers to a bitfield is essentially
/// an aspect of the value-kind type system.
bool refersToBitField() const { return getObjectKind() == OK_BitField; }
/// If this expression refers to a bit-field, retrieve the
/// declaration of that bit-field.
///
/// Note that this returns a non-null pointer in subtly different
/// places than refersToBitField returns true. In particular, this can
/// return a non-null pointer even for r-values loaded from
/// bit-fields, but it will return null for a conditional bit-field.
FieldDecl *getSourceBitField();
const FieldDecl *getSourceBitField() const {
return const_cast(this)->getSourceBitField();
}
Decl *getReferencedDeclOfCallee();
const Decl *getReferencedDeclOfCallee() const {
return const_cast(this)->getReferencedDeclOfCallee();
}
/// If this expression is an l-value for an Objective C
/// property, find the underlying property reference expression.
const ObjCPropertyRefExpr *getObjCProperty() const;
/// Check if this expression is the ObjC 'self' implicit parameter.
bool isObjCSelfExpr() const;
/// Returns whether this expression refers to a vector element.
bool refersToVectorElement() const;
/// Returns whether this expression refers to a global register
/// variable.
bool refersToGlobalRegisterVar() const;
/// Returns whether this expression has a placeholder type.
bool hasPlaceholderType() const {
return getType()->isPlaceholderType();
}
/// Returns whether this expression has a specific placeholder type.
bool hasPlaceholderType(BuiltinType::Kind K) const {
assert(BuiltinType::isPlaceholderTypeKind(K));
if (const BuiltinType *BT = dyn_cast(getType()))
return BT->getKind() == K;
return false;
}
/// isKnownToHaveBooleanValue - Return true if this is an integer expression
/// that is known to return 0 or 1. This happens for _Bool/bool expressions
/// but also int expressions which are produced by things like comparisons in
/// C.
bool isKnownToHaveBooleanValue() const;
/// isIntegerConstantExpr - Return true if this expression is a valid integer
/// constant expression, and, if so, return its value in Result. If not a
/// valid i-c-e, return false and fill in Loc (if specified) with the location
/// of the invalid expression.
///
/// Note: This does not perform the implicit conversions required by C++11
/// [expr.const]p5.
bool isIntegerConstantExpr(llvm::APSInt &Result, const ASTContext &Ctx,
SourceLocation *Loc = nullptr,
bool isEvaluated = true) const;
bool isIntegerConstantExpr(const ASTContext &Ctx,
SourceLocation *Loc = nullptr) const;
/// isCXX98IntegralConstantExpr - Return true if this expression is an
/// integral constant expression in C++98. Can only be used in C++.
bool isCXX98IntegralConstantExpr(const ASTContext &Ctx) const;
/// isCXX11ConstantExpr - Return true if this expression is a constant
/// expression in C++11. Can only be used in C++.
///
/// Note: This does not perform the implicit conversions required by C++11
/// [expr.const]p5.
bool isCXX11ConstantExpr(const ASTContext &Ctx, APValue *Result = nullptr,
SourceLocation *Loc = nullptr) const;
/// isPotentialConstantExpr - Return true if this function's definition
/// might be usable in a constant expression in C++11, if it were marked
/// constexpr. Return false if the function can never produce a constant
/// expression, along with diagnostics describing why not.
static bool isPotentialConstantExpr(const FunctionDecl *FD,
SmallVectorImpl<
PartialDiagnosticAt> &Diags);
/// isPotentialConstantExprUnevaluted - Return true if this expression might
/// be usable in a constant expression in C++11 in an unevaluated context, if
/// it were in function FD marked constexpr. Return false if the function can
/// never produce a constant expression, along with diagnostics describing
/// why not.
static bool isPotentialConstantExprUnevaluated(Expr *E,
const FunctionDecl *FD,
SmallVectorImpl<
PartialDiagnosticAt> &Diags);
/// isConstantInitializer - Returns true if this expression can be emitted to
/// IR as a constant, and thus can be used as a constant initializer in C.
/// If this expression is not constant and Culprit is non-null,
/// it is used to store the address of first non constant expr.
bool isConstantInitializer(ASTContext &Ctx, bool ForRef,
const Expr **Culprit = nullptr) const;
/// EvalStatus is a struct with detailed info about an evaluation in progress.
struct EvalStatus {
/// Whether the evaluated expression has side effects.
/// For example, (f() && 0) can be folded, but it still has side effects.
bool HasSideEffects;
/// Whether the evaluation hit undefined behavior.
/// For example, 1.0 / 0.0 can be folded to Inf, but has undefined behavior.
/// Likewise, INT_MAX + 1 can be folded to INT_MIN, but has UB.
bool HasUndefinedBehavior;
/// Diag - If this is non-null, it will be filled in with a stack of notes
/// indicating why evaluation failed (or why it failed to produce a constant
/// expression).
/// If the expression is unfoldable, the notes will indicate why it's not
/// foldable. If the expression is foldable, but not a constant expression,
/// the notes will describes why it isn't a constant expression. If the
/// expression *is* a constant expression, no notes will be produced.
SmallVectorImpl *Diag;
EvalStatus()
: HasSideEffects(false), HasUndefinedBehavior(false), Diag(nullptr) {}
// hasSideEffects - Return true if the evaluated expression has
// side effects.
bool hasSideEffects() const {
return HasSideEffects;
}
};
/// EvalResult is a struct with detailed info about an evaluated expression.
struct EvalResult : EvalStatus {
/// Val - This is the value the expression can be folded to.
APValue Val;
// isGlobalLValue - Return true if the evaluated lvalue expression
// is global.
bool isGlobalLValue() const;
};
/// EvaluateAsRValue - Return true if this is a constant which we can fold to
/// an rvalue using any crazy technique (that has nothing to do with language
/// standards) that we want to, even if the expression has side-effects. If
/// this function returns true, it returns the folded constant in Result. If
/// the expression is a glvalue, an lvalue-to-rvalue conversion will be
/// applied.
bool EvaluateAsRValue(EvalResult &Result, const ASTContext &Ctx,
bool InConstantContext = false) const;
/// EvaluateAsBooleanCondition - Return true if this is a constant
/// which we can fold and convert to a boolean condition using
/// any crazy technique that we want to, even if the expression has
/// side-effects.
bool EvaluateAsBooleanCondition(bool &Result, const ASTContext &Ctx) const;
enum SideEffectsKind {
SE_NoSideEffects, ///< Strictly evaluate the expression.
SE_AllowUndefinedBehavior, ///< Allow UB that we can give a value, but not
///< arbitrary unmodeled side effects.
SE_AllowSideEffects ///< Allow any unmodeled side effect.
};
/// EvaluateAsInt - Return true if this is a constant which we can fold and
/// convert to an integer, using any crazy technique that we want to.
bool EvaluateAsInt(EvalResult &Result, const ASTContext &Ctx,
SideEffectsKind AllowSideEffects = SE_NoSideEffects) const;
/// EvaluateAsFloat - Return true if this is a constant which we can fold and
/// convert to a floating point value, using any crazy technique that we
/// want to.
bool
EvaluateAsFloat(llvm::APFloat &Result, const ASTContext &Ctx,
SideEffectsKind AllowSideEffects = SE_NoSideEffects) const;
/// isEvaluatable - Call EvaluateAsRValue to see if this expression can be
/// constant folded without side-effects, but discard the result.
bool isEvaluatable(const ASTContext &Ctx,
SideEffectsKind AllowSideEffects = SE_NoSideEffects) const;
/// HasSideEffects - This routine returns true for all those expressions
/// which have any effect other than producing a value. Example is a function
/// call, volatile variable read, or throwing an exception. If
/// IncludePossibleEffects is false, this call treats certain expressions with
/// potential side effects (such as function call-like expressions,
/// instantiation-dependent expressions, or invocations from a macro) as not
/// having side effects.
bool HasSideEffects(const ASTContext &Ctx,
bool IncludePossibleEffects = true) const;
/// Determine whether this expression involves a call to any function
/// that is not trivial.
bool hasNonTrivialCall(const ASTContext &Ctx) const;
/// EvaluateKnownConstInt - Call EvaluateAsRValue and return the folded
/// integer. This must be called on an expression that constant folds to an
/// integer.
llvm::APSInt EvaluateKnownConstInt(
const ASTContext &Ctx,
SmallVectorImpl *Diag = nullptr) const;
llvm::APSInt EvaluateKnownConstIntCheckOverflow(
const ASTContext &Ctx,
SmallVectorImpl *Diag = nullptr) const;
void EvaluateForOverflow(const ASTContext &Ctx) const;
/// EvaluateAsLValue - Evaluate an expression to see if we can fold it to an
/// lvalue with link time known address, with no side-effects.
bool EvaluateAsLValue(EvalResult &Result, const ASTContext &Ctx) const;
/// EvaluateAsInitializer - Evaluate an expression as if it were the
/// initializer of the given declaration. Returns true if the initializer
/// can be folded to a constant, and produces any relevant notes. In C++11,
/// notes will be produced if the expression is not a constant expression.
bool EvaluateAsInitializer(APValue &Result, const ASTContext &Ctx,
const VarDecl *VD,
SmallVectorImpl &Notes) const;
/// EvaluateWithSubstitution - Evaluate an expression as if from the context
/// of a call to the given function with the given arguments, inside an
/// unevaluated context. Returns true if the expression could be folded to a
/// constant.
bool EvaluateWithSubstitution(APValue &Value, ASTContext &Ctx,
const FunctionDecl *Callee,
ArrayRef Args,
const Expr *This = nullptr) const;
/// Indicates how the constant expression will be used.
enum ConstExprUsage { EvaluateForCodeGen, EvaluateForMangling };
/// Evaluate an expression that is required to be a constant expression.
bool EvaluateAsConstantExpr(EvalResult &Result, ConstExprUsage Usage,
const ASTContext &Ctx) const;
/// If the current Expr is a pointer, this will try to statically
/// determine the number of bytes available where the pointer is pointing.
/// Returns true if all of the above holds and we were able to figure out the
/// size, false otherwise.
///
/// \param Type - How to evaluate the size of the Expr, as defined by the
/// "type" parameter of __builtin_object_size
bool tryEvaluateObjectSize(uint64_t &Result, ASTContext &Ctx,
unsigned Type) const;
/// Enumeration used to describe the kind of Null pointer constant
/// returned from \c isNullPointerConstant().
enum NullPointerConstantKind {
/// Expression is not a Null pointer constant.
NPCK_NotNull = 0,
/// Expression is a Null pointer constant built from a zero integer
/// expression that is not a simple, possibly parenthesized, zero literal.
/// C++ Core Issue 903 will classify these expressions as "not pointers"
/// once it is adopted.
/// http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#903
NPCK_ZeroExpression,
/// Expression is a Null pointer constant built from a literal zero.
NPCK_ZeroLiteral,
/// Expression is a C++11 nullptr.
NPCK_CXX11_nullptr,
/// Expression is a GNU-style __null constant.
NPCK_GNUNull
};
/// Enumeration used to describe how \c isNullPointerConstant()
/// should cope with value-dependent expressions.
enum NullPointerConstantValueDependence {
/// Specifies that the expression should never be value-dependent.
NPC_NeverValueDependent = 0,
/// Specifies that a value-dependent expression of integral or
/// dependent type should be considered a null pointer constant.
NPC_ValueDependentIsNull,
/// Specifies that a value-dependent expression should be considered
/// to never be a null pointer constant.
NPC_ValueDependentIsNotNull
};
/// isNullPointerConstant - C99 6.3.2.3p3 - Test if this reduces down to
/// a Null pointer constant. The return value can further distinguish the
/// kind of NULL pointer constant that was detected.
NullPointerConstantKind isNullPointerConstant(
ASTContext &Ctx,
NullPointerConstantValueDependence NPC) const;
/// isOBJCGCCandidate - Return true if this expression may be used in a read/
/// write barrier.
bool isOBJCGCCandidate(ASTContext &Ctx) const;
/// Returns true if this expression is a bound member function.
bool isBoundMemberFunction(ASTContext &Ctx) const;
/// Given an expression of bound-member type, find the type
/// of the member. Returns null if this is an *overloaded* bound
/// member expression.
static QualType findBoundMemberType(const Expr *expr);
/// IgnoreImpCasts - Skip past any implicit casts which might
/// surround this expression. Only skips ImplicitCastExprs.
Expr *IgnoreImpCasts() LLVM_READONLY;
/// IgnoreImplicit - Skip past any implicit AST nodes which might
/// surround this expression.
Expr *IgnoreImplicit() LLVM_READONLY {
return cast(Stmt::IgnoreImplicit());
}
const Expr *IgnoreImplicit() const LLVM_READONLY {
return const_cast(this)->IgnoreImplicit();
}
/// IgnoreParens - Ignore parentheses. If this Expr is a ParenExpr, return
/// its subexpression. If that subexpression is also a ParenExpr,
/// then this method recursively returns its subexpression, and so forth.
/// Otherwise, the method returns the current Expr.
Expr *IgnoreParens() LLVM_READONLY;
/// IgnoreParenCasts - Ignore parentheses and casts. Strip off any ParenExpr
/// or CastExprs, returning their operand.
Expr *IgnoreParenCasts() LLVM_READONLY;
/// Ignore casts. Strip off any CastExprs, returning their operand.
Expr *IgnoreCasts() LLVM_READONLY;
/// IgnoreParenImpCasts - Ignore parentheses and implicit casts. Strip off
/// any ParenExpr or ImplicitCastExprs, returning their operand.
Expr *IgnoreParenImpCasts() LLVM_READONLY;
/// IgnoreConversionOperator - Ignore conversion operator. If this Expr is a
/// call to a conversion operator, return the argument.
Expr *IgnoreConversionOperator() LLVM_READONLY;
const Expr *IgnoreConversionOperator() const LLVM_READONLY {
return const_cast(this)->IgnoreConversionOperator();
}
const Expr *IgnoreParenImpCasts() const LLVM_READONLY {
return const_cast(this)->IgnoreParenImpCasts();
}
/// Ignore parentheses and lvalue casts. Strip off any ParenExpr and
/// CastExprs that represent lvalue casts, returning their operand.
Expr *IgnoreParenLValueCasts() LLVM_READONLY;
const Expr *IgnoreParenLValueCasts() const LLVM_READONLY {
return const_cast(this)->IgnoreParenLValueCasts();
}
/// IgnoreParenNoopCasts - Ignore parentheses and casts that do not change the
/// value (including ptr->int casts of the same size). Strip off any
/// ParenExpr or CastExprs, returning their operand.
Expr *IgnoreParenNoopCasts(ASTContext &Ctx) LLVM_READONLY;
/// Ignore parentheses and derived-to-base casts.
Expr *ignoreParenBaseCasts() LLVM_READONLY;
const Expr *ignoreParenBaseCasts() const LLVM_READONLY {
return const_cast(this)->ignoreParenBaseCasts();
}
/// Determine whether this expression is a default function argument.
///
/// Default arguments are implicitly generated in the abstract syntax tree
/// by semantic analysis for function calls, object constructions, etc. in
/// C++. Default arguments are represented by \c CXXDefaultArgExpr nodes;
/// this routine also looks through any implicit casts to determine whether
/// the expression is a default argument.
bool isDefaultArgument() const;
/// Determine whether the result of this expression is a
/// temporary object of the given class type.
bool isTemporaryObject(ASTContext &Ctx, const CXXRecordDecl *TempTy) const;
/// Whether this expression is an implicit reference to 'this' in C++.
bool isImplicitCXXThis() const;
const Expr *IgnoreImpCasts() const LLVM_READONLY {
return const_cast(this)->IgnoreImpCasts();
}
const Expr *IgnoreParens() const LLVM_READONLY {
return const_cast(this)->IgnoreParens();
}
const Expr *IgnoreParenCasts() const LLVM_READONLY {
return const_cast(this)->IgnoreParenCasts();
}
/// Strip off casts, but keep parentheses.
const Expr *IgnoreCasts() const LLVM_READONLY {
return const_cast(this)->IgnoreCasts();
}
const Expr *IgnoreParenNoopCasts(ASTContext &Ctx) const LLVM_READONLY {
return const_cast(this)->IgnoreParenNoopCasts(Ctx);
}
static bool hasAnyTypeDependentArguments(ArrayRef Exprs);
/// For an expression of class type or pointer to class type,
/// return the most derived class decl the expression is known to refer to.
///
/// If this expression is a cast, this method looks through it to find the
/// most derived decl that can be inferred from the expression.
/// This is valid because derived-to-base conversions have undefined
/// behavior if the object isn't dynamically of the derived type.
const CXXRecordDecl *getBestDynamicClassType() const;
/// Get the inner expression that determines the best dynamic class.
/// If this is a prvalue, we guarantee that it is of the most-derived type
/// for the object itself.
const Expr *getBestDynamicClassTypeExpr() const;
/// Walk outwards from an expression we want to bind a reference to and
/// find the expression whose lifetime needs to be extended. Record
/// the LHSs of comma expressions and adjustments needed along the path.
const Expr *skipRValueSubobjectAdjustments(
SmallVectorImpl &CommaLHS,
SmallVectorImpl &Adjustments) const;
const Expr *skipRValueSubobjectAdjustments() const {
SmallVector CommaLHSs;
SmallVector Adjustments;
return skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
}
static bool classof(const Stmt *T) {
return T->getStmtClass() >= firstExprConstant &&
T->getStmtClass() <= lastExprConstant;
}
};
//===----------------------------------------------------------------------===//
// Wrapper Expressions.
//===----------------------------------------------------------------------===//
/// FullExpr - Represents a "full-expression" node.
class FullExpr : public Expr {
protected:
Stmt *SubExpr;
FullExpr(StmtClass SC, Expr *subexpr)
: Expr(SC, subexpr->getType(),
subexpr->getValueKind(), subexpr->getObjectKind(),
subexpr->isTypeDependent(), subexpr->isValueDependent(),
subexpr->isInstantiationDependent(),
subexpr->containsUnexpandedParameterPack()), SubExpr(subexpr) {}
FullExpr(StmtClass SC, EmptyShell Empty)
: Expr(SC, Empty) {}
public:
const Expr *getSubExpr() const { return cast(SubExpr); }
Expr *getSubExpr() { return cast(SubExpr); }
/// As with any mutator of the AST, be very careful when modifying an
/// existing AST to preserve its invariants.
void setSubExpr(Expr *E) { SubExpr = E; }
static bool classof(const Stmt *T) {
return T->getStmtClass() >= firstFullExprConstant &&
T->getStmtClass() <= lastFullExprConstant;
}
};
/// ConstantExpr - An expression that occurs in a constant context.
class ConstantExpr : public FullExpr {
ConstantExpr(Expr *subexpr)
: FullExpr(ConstantExprClass, subexpr) {}
public:
static ConstantExpr *Create(const ASTContext &Context, Expr *E) {
assert(!isa(E));
return new (Context) ConstantExpr(E);
}
/// Build an empty constant expression wrapper.
explicit ConstantExpr(EmptyShell Empty)
: FullExpr(ConstantExprClass, Empty) {}
SourceLocation getBeginLoc() const LLVM_READONLY {
return SubExpr->getBeginLoc();
}
SourceLocation getEndLoc() const LLVM_READONLY {
return SubExpr->getEndLoc();
}
static bool classof(const Stmt *T) {
return T->getStmtClass() == ConstantExprClass;
}
// Iterators
child_range children() { return child_range(&SubExpr, &SubExpr+1); }
const_child_range children() const {
return const_child_range(&SubExpr, &SubExpr + 1);
}
};
//===----------------------------------------------------------------------===//
// Primary Expressions.
//===----------------------------------------------------------------------===//
/// OpaqueValueExpr - An expression referring to an opaque object of a
/// fixed type and value class. These don't correspond to concrete
/// syntax; instead they're used to express operations (usually copy
/// operations) on values whose source is generally obvious from
/// context.
class OpaqueValueExpr : public Expr {
friend class ASTStmtReader;
Expr *SourceExpr;
public:
OpaqueValueExpr(SourceLocation Loc, QualType T, ExprValueKind VK,
ExprObjectKind OK = OK_Ordinary,
Expr *SourceExpr = nullptr)
: Expr(OpaqueValueExprClass, T, VK, OK,
T->isDependentType() ||
(SourceExpr && SourceExpr->isTypeDependent()),
T->isDependentType() ||
(SourceExpr && SourceExpr->isValueDependent()),
T->isInstantiationDependentType() ||
(SourceExpr && SourceExpr->isInstantiationDependent()),
false),
SourceExpr(SourceExpr) {
setIsUnique(false);
OpaqueValueExprBits.Loc = Loc;
}
/// Given an expression which invokes a copy constructor --- i.e. a
/// CXXConstructExpr, possibly wrapped in an ExprWithCleanups ---
/// find the OpaqueValueExpr that's the source of the construction.
static const OpaqueValueExpr *findInCopyConstruct(const Expr *expr);
explicit OpaqueValueExpr(EmptyShell Empty)
: Expr(OpaqueValueExprClass, Empty) {}
/// Retrieve the location of this expression.
SourceLocation getLocation() const { return OpaqueValueExprBits.Loc; }
SourceLocation getBeginLoc() const LLVM_READONLY {
return SourceExpr ? SourceExpr->getBeginLoc() : getLocation();
}
SourceLocation getEndLoc() const LLVM_READONLY {
return SourceExpr ? SourceExpr->getEndLoc() : getLocation();
}
SourceLocation getExprLoc() const LLVM_READONLY {
return SourceExpr ? SourceExpr->getExprLoc() : getLocation();
}
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
/// The source expression of an opaque value expression is the
/// expression which originally generated the value. This is
/// provided as a convenience for analyses that don't wish to
/// precisely model the execution behavior of the program.
///
/// The source expression is typically set when building the
/// expression which binds the opaque value expression in the first
/// place.
Expr *getSourceExpr() const { return SourceExpr; }
void setIsUnique(bool V) {
assert((!V || SourceExpr) &&
"unique OVEs are expected to have source expressions");
OpaqueValueExprBits.IsUnique = V;
}
bool isUnique() const { return OpaqueValueExprBits.IsUnique; }
static bool classof(const Stmt *T) {
return T->getStmtClass() == OpaqueValueExprClass;
}
};
/// A reference to a declared variable, function, enum, etc.
/// [C99 6.5.1p2]
///
/// This encodes all the information about how a declaration is referenced
/// within an expression.
///
/// There are several optional constructs attached to DeclRefExprs only when
/// they apply in order to conserve memory. These are laid out past the end of
/// the object, and flags in the DeclRefExprBitfield track whether they exist:
///
/// DeclRefExprBits.HasQualifier:
/// Specifies when this declaration reference expression has a C++
/// nested-name-specifier.
/// DeclRefExprBits.HasFoundDecl:
/// Specifies when this declaration reference expression has a record of
/// a NamedDecl (different from the referenced ValueDecl) which was found
/// during name lookup and/or overload resolution.
/// DeclRefExprBits.HasTemplateKWAndArgsInfo:
/// Specifies when this declaration reference expression has an explicit
/// C++ template keyword and/or template argument list.
/// DeclRefExprBits.RefersToEnclosingVariableOrCapture
/// Specifies when this declaration reference expression (validly)
/// refers to an enclosed local or a captured variable.
class DeclRefExpr final
: public Expr,
private llvm::TrailingObjects {
friend class ASTStmtReader;
friend class ASTStmtWriter;
friend TrailingObjects;
/// The declaration that we are referencing.
ValueDecl *D;
/// Provides source/type location info for the declaration name
/// embedded in D.
DeclarationNameLoc DNLoc;
size_t numTrailingObjects(OverloadToken) const {
return hasQualifier();
}
size_t numTrailingObjects(OverloadToken) const {
return hasFoundDecl();
}
size_t numTrailingObjects(OverloadToken) const {
return hasTemplateKWAndArgsInfo();
}
/// Test whether there is a distinct FoundDecl attached to the end of
/// this DRE.
bool hasFoundDecl() const { return DeclRefExprBits.HasFoundDecl; }
DeclRefExpr(const ASTContext &Ctx, NestedNameSpecifierLoc QualifierLoc,
SourceLocation TemplateKWLoc, ValueDecl *D,
bool RefersToEnlosingVariableOrCapture,
const DeclarationNameInfo &NameInfo, NamedDecl *FoundD,
const TemplateArgumentListInfo *TemplateArgs, QualType T,
ExprValueKind VK);
/// Construct an empty declaration reference expression.
explicit DeclRefExpr(EmptyShell Empty) : Expr(DeclRefExprClass, Empty) {}
/// Computes the type- and value-dependence flags for this
/// declaration reference expression.
void computeDependence(const ASTContext &Ctx);
public:
DeclRefExpr(const ASTContext &Ctx, ValueDecl *D,
bool RefersToEnclosingVariableOrCapture, QualType T,
ExprValueKind VK, SourceLocation L,
const DeclarationNameLoc &LocInfo = DeclarationNameLoc());
static DeclRefExpr *
Create(const ASTContext &Context, NestedNameSpecifierLoc QualifierLoc,
SourceLocation TemplateKWLoc, ValueDecl *D,
bool RefersToEnclosingVariableOrCapture, SourceLocation NameLoc,
QualType T, ExprValueKind VK, NamedDecl *FoundD = nullptr,
const TemplateArgumentListInfo *TemplateArgs = nullptr);
static DeclRefExpr *
Create(const ASTContext &Context, NestedNameSpecifierLoc QualifierLoc,
SourceLocation TemplateKWLoc, ValueDecl *D,
bool RefersToEnclosingVariableOrCapture,
const DeclarationNameInfo &NameInfo, QualType T, ExprValueKind VK,
NamedDecl *FoundD = nullptr,
const TemplateArgumentListInfo *TemplateArgs = nullptr);
/// Construct an empty declaration reference expression.
static DeclRefExpr *CreateEmpty(const ASTContext &Context, bool HasQualifier,
bool HasFoundDecl,
bool HasTemplateKWAndArgsInfo,
unsigned NumTemplateArgs);
ValueDecl *getDecl() { return D; }
const ValueDecl *getDecl() const { return D; }
void setDecl(ValueDecl *NewD) { D = NewD; }
DeclarationNameInfo getNameInfo() const {
return DeclarationNameInfo(getDecl()->getDeclName(), getLocation(), DNLoc);
}
SourceLocation getLocation() const { return DeclRefExprBits.Loc; }
void setLocation(SourceLocation L) { DeclRefExprBits.Loc = L; }
SourceLocation getBeginLoc() const LLVM_READONLY;
SourceLocation getEndLoc() const LLVM_READONLY;
/// Determine whether this declaration reference was preceded by a
/// C++ nested-name-specifier, e.g., \c N::foo.
bool hasQualifier() const { return DeclRefExprBits.HasQualifier; }
/// If the name was qualified, retrieves the nested-name-specifier
/// that precedes the name, with source-location information.
NestedNameSpecifierLoc getQualifierLoc() const {
if (!hasQualifier())
return NestedNameSpecifierLoc();
return *getTrailingObjects();
}
/// If the name was qualified, retrieves the nested-name-specifier
/// that precedes the name. Otherwise, returns NULL.
NestedNameSpecifier *getQualifier() const {
return getQualifierLoc().getNestedNameSpecifier();
}
/// Get the NamedDecl through which this reference occurred.
///
/// This Decl may be different from the ValueDecl actually referred to in the
/// presence of using declarations, etc. It always returns non-NULL, and may
/// simple return the ValueDecl when appropriate.
NamedDecl *getFoundDecl() {
return hasFoundDecl() ? *getTrailingObjects() : D;
}
/// Get the NamedDecl through which this reference occurred.
/// See non-const variant.
const NamedDecl *getFoundDecl() const {
return hasFoundDecl() ? *getTrailingObjects() : D;
}
bool hasTemplateKWAndArgsInfo() const {
return DeclRefExprBits.HasTemplateKWAndArgsInfo;
}
/// Retrieve the location of the template keyword preceding
/// this name, if any.
SourceLocation getTemplateKeywordLoc() const {
if (!hasTemplateKWAndArgsInfo())
return SourceLocation();
return getTrailingObjects()->TemplateKWLoc;
}
/// Retrieve the location of the left angle bracket starting the
/// explicit template argument list following the name, if any.
SourceLocation getLAngleLoc() const {
if (!hasTemplateKWAndArgsInfo())
return SourceLocation();
return getTrailingObjects()->LAngleLoc;
}
/// Retrieve the location of the right angle bracket ending the
/// explicit template argument list following the name, if any.
SourceLocation getRAngleLoc() const {
if (!hasTemplateKWAndArgsInfo())
return SourceLocation();
return getTrailingObjects()->RAngleLoc;
}
/// Determines whether the name in this declaration reference
/// was preceded by the template keyword.
bool hasTemplateKeyword() const { return getTemplateKeywordLoc().isValid(); }
/// Determines whether this declaration reference was followed by an
/// explicit template argument list.
bool hasExplicitTemplateArgs() const { return getLAngleLoc().isValid(); }
/// Copies the template arguments (if present) into the given
/// structure.
void copyTemplateArgumentsInto(TemplateArgumentListInfo &List) const {
if (hasExplicitTemplateArgs())
getTrailingObjects()->copyInto(
getTrailingObjects(), List);
}
/// Retrieve the template arguments provided as part of this
/// template-id.
const TemplateArgumentLoc *getTemplateArgs() const {
if (!hasExplicitTemplateArgs())
return nullptr;
return getTrailingObjects();
}
/// Retrieve the number of template arguments provided as part of this
/// template-id.
unsigned getNumTemplateArgs() const {
if (!hasExplicitTemplateArgs())
return 0;
return getTrailingObjects()->NumTemplateArgs;
}
ArrayRef template_arguments() const {
return {getTemplateArgs(), getNumTemplateArgs()};
}
/// Returns true if this expression refers to a function that
/// was resolved from an overloaded set having size greater than 1.
bool hadMultipleCandidates() const {
return DeclRefExprBits.HadMultipleCandidates;
}
/// Sets the flag telling whether this expression refers to
/// a function that was resolved from an overloaded set having size
/// greater than 1.
void setHadMultipleCandidates(bool V = true) {
DeclRefExprBits.HadMultipleCandidates = V;
}
/// Does this DeclRefExpr refer to an enclosing local or a captured
/// variable?
bool refersToEnclosingVariableOrCapture() const {
return DeclRefExprBits.RefersToEnclosingVariableOrCapture;
}
static bool classof(const Stmt *T) {
return T->getStmtClass() == DeclRefExprClass;
}
// Iterators
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
};
/// Used by IntegerLiteral/FloatingLiteral to store the numeric without
/// leaking memory.
///
/// For large floats/integers, APFloat/APInt will allocate memory from the heap
/// to represent these numbers. Unfortunately, when we use a BumpPtrAllocator
/// to allocate IntegerLiteral/FloatingLiteral nodes the memory associated with
/// the APFloat/APInt values will never get freed. APNumericStorage uses
/// ASTContext's allocator for memory allocation.
class APNumericStorage {
union {
uint64_t VAL; ///< Used to store the <= 64 bits integer value.
uint64_t *pVal; ///< Used to store the >64 bits integer value.
};
unsigned BitWidth;
bool hasAllocation() const { return llvm::APInt::getNumWords(BitWidth) > 1; }
APNumericStorage(const APNumericStorage &) = delete;
void operator=(const APNumericStorage &) = delete;
protected:
APNumericStorage() : VAL(0), BitWidth(0) { }
llvm::APInt getIntValue() const {
unsigned NumWords = llvm::APInt::getNumWords(BitWidth);
if (NumWords > 1)
return llvm::APInt(BitWidth, NumWords, pVal);
else
return llvm::APInt(BitWidth, VAL);
}
void setIntValue(const ASTContext &C, const llvm::APInt &Val);
};
class APIntStorage : private APNumericStorage {
public:
llvm::APInt getValue() const { return getIntValue(); }
void setValue(const ASTContext &C, const llvm::APInt &Val) {
setIntValue(C, Val);
}
};
class APFloatStorage : private APNumericStorage {
public:
llvm::APFloat getValue(const llvm::fltSemantics &Semantics) const {
return llvm::APFloat(Semantics, getIntValue());
}
void setValue(const ASTContext &C, const llvm::APFloat &Val) {
setIntValue(C, Val.bitcastToAPInt());
}
};
class IntegerLiteral : public Expr, public APIntStorage {
SourceLocation Loc;
/// Construct an empty integer literal.
explicit IntegerLiteral(EmptyShell Empty)
: Expr(IntegerLiteralClass, Empty) { }
public:
// type should be IntTy, LongTy, LongLongTy, UnsignedIntTy, UnsignedLongTy,
// or UnsignedLongLongTy
IntegerLiteral(const ASTContext &C, const llvm::APInt &V, QualType type,
SourceLocation l);
/// Returns a new integer literal with value 'V' and type 'type'.
/// \param type - either IntTy, LongTy, LongLongTy, UnsignedIntTy,
/// UnsignedLongTy, or UnsignedLongLongTy which should match the size of V
/// \param V - the value that the returned integer literal contains.
static IntegerLiteral *Create(const ASTContext &C, const llvm::APInt &V,
QualType type, SourceLocation l);
/// Returns a new empty integer literal.
static IntegerLiteral *Create(const ASTContext &C, EmptyShell Empty);
SourceLocation getBeginLoc() const LLVM_READONLY { return Loc; }
SourceLocation getEndLoc() const LLVM_READONLY { return Loc; }
/// Retrieve the location of the literal.
SourceLocation getLocation() const { return Loc; }
void setLocation(SourceLocation Location) { Loc = Location; }
static bool classof(const Stmt *T) {
return T->getStmtClass() == IntegerLiteralClass;
}
// Iterators
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
};
class FixedPointLiteral : public Expr, public APIntStorage {
SourceLocation Loc;
unsigned Scale;
/// \brief Construct an empty integer literal.
explicit FixedPointLiteral(EmptyShell Empty)
: Expr(FixedPointLiteralClass, Empty) {}
public:
FixedPointLiteral(const ASTContext &C, const llvm::APInt &V, QualType type,
SourceLocation l, unsigned Scale);
// Store the int as is without any bit shifting.
static FixedPointLiteral *CreateFromRawInt(const ASTContext &C,
const llvm::APInt &V,
QualType type, SourceLocation l,
unsigned Scale);
SourceLocation getBeginLoc() const LLVM_READONLY { return Loc; }
SourceLocation getEndLoc() const LLVM_READONLY { return Loc; }
/// \brief Retrieve the location of the literal.
SourceLocation getLocation() const { return Loc; }
void setLocation(SourceLocation Location) { Loc = Location; }
static bool classof(const Stmt *T) {
return T->getStmtClass() == FixedPointLiteralClass;
}
std::string getValueAsString(unsigned Radix) const;
// Iterators
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
};
class CharacterLiteral : public Expr {
public:
enum CharacterKind {
Ascii,
Wide,
UTF8,
UTF16,
UTF32
};
private:
unsigned Value;
SourceLocation Loc;
public:
// type should be IntTy
CharacterLiteral(unsigned value, CharacterKind kind, QualType type,
SourceLocation l)
: Expr(CharacterLiteralClass, type, VK_RValue, OK_Ordinary, false, false,
false, false),
Value(value), Loc(l) {
CharacterLiteralBits.Kind = kind;
}
/// Construct an empty character literal.
CharacterLiteral(EmptyShell Empty) : Expr(CharacterLiteralClass, Empty) { }
SourceLocation getLocation() const { return Loc; }
CharacterKind getKind() const {
return static_cast(CharacterLiteralBits.Kind);
}
SourceLocation getBeginLoc() const LLVM_READONLY { return Loc; }
SourceLocation getEndLoc() const LLVM_READONLY { return Loc; }
unsigned getValue() const { return Value; }
void setLocation(SourceLocation Location) { Loc = Location; }
void setKind(CharacterKind kind) { CharacterLiteralBits.Kind = kind; }
void setValue(unsigned Val) { Value = Val; }
static bool classof(const Stmt *T) {
return T->getStmtClass() == CharacterLiteralClass;
}
// Iterators
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
};
class FloatingLiteral : public Expr, private APFloatStorage {
SourceLocation Loc;
FloatingLiteral(const ASTContext &C, const llvm::APFloat &V, bool isexact,
QualType Type, SourceLocation L);
/// Construct an empty floating-point literal.
explicit FloatingLiteral(const ASTContext &C, EmptyShell Empty);
public:
static FloatingLiteral *Create(const ASTContext &C, const llvm::APFloat &V,
bool isexact, QualType Type, SourceLocation L);
static FloatingLiteral *Create(const ASTContext &C, EmptyShell Empty);
llvm::APFloat getValue() const {
return APFloatStorage::getValue(getSemantics());
}
void setValue(const ASTContext &C, const llvm::APFloat &Val) {
assert(&getSemantics() == &Val.getSemantics() && "Inconsistent semantics");
APFloatStorage::setValue(C, Val);
}
/// Get a raw enumeration value representing the floating-point semantics of
/// this literal (32-bit IEEE, x87, ...), suitable for serialisation.
APFloatSemantics getRawSemantics() const {
return static_cast(FloatingLiteralBits.Semantics);
}
/// Set the raw enumeration value representing the floating-point semantics of
/// this literal (32-bit IEEE, x87, ...), suitable for serialisation.
void setRawSemantics(APFloatSemantics Sem) {
FloatingLiteralBits.Semantics = Sem;
}
/// Return the APFloat semantics this literal uses.
const llvm::fltSemantics &getSemantics() const;
/// Set the APFloat semantics this literal uses.
void setSemantics(const llvm::fltSemantics &Sem);
bool isExact() const { return FloatingLiteralBits.IsExact; }
void setExact(bool E) { FloatingLiteralBits.IsExact = E; }
/// getValueAsApproximateDouble - This returns the value as an inaccurate
/// double. Note that this may cause loss of precision, but is useful for
/// debugging dumps, etc.
double getValueAsApproximateDouble() const;
SourceLocation getLocation() const { return Loc; }
void setLocation(SourceLocation L) { Loc = L; }
SourceLocation getBeginLoc() const LLVM_READONLY { return Loc; }
SourceLocation getEndLoc() const LLVM_READONLY { return Loc; }
static bool classof(const Stmt *T) {
return T->getStmtClass() == FloatingLiteralClass;
}
// Iterators
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
};
/// ImaginaryLiteral - We support imaginary integer and floating point literals,
/// like "1.0i". We represent these as a wrapper around FloatingLiteral and
/// IntegerLiteral classes. Instances of this class always have a Complex type
/// whose element type matches the subexpression.
///
class ImaginaryLiteral : public Expr {
Stmt *Val;
public:
ImaginaryLiteral(Expr *val, QualType Ty)
: Expr(ImaginaryLiteralClass, Ty, VK_RValue, OK_Ordinary, false, false,
false, false),
Val(val) {}
/// Build an empty imaginary literal.
explicit ImaginaryLiteral(EmptyShell Empty)
: Expr(ImaginaryLiteralClass, Empty) { }
const Expr *getSubExpr() const { return cast(Val); }
Expr *getSubExpr() { return cast(Val); }
void setSubExpr(Expr *E) { Val = E; }
SourceLocation getBeginLoc() const LLVM_READONLY {
return Val->getBeginLoc();
}
SourceLocation getEndLoc() const LLVM_READONLY { return Val->getEndLoc(); }
static bool classof(const Stmt *T) {
return T->getStmtClass() == ImaginaryLiteralClass;
}
// Iterators
child_range children() { return child_range(&Val, &Val+1); }
const_child_range children() const {
return const_child_range(&Val, &Val + 1);
}
};
/// StringLiteral - This represents a string literal expression, e.g. "foo"
/// or L"bar" (wide strings). The actual string data can be obtained with
/// getBytes() and is NOT null-terminated. The length of the string data is
/// determined by calling getByteLength().
///
/// The C type for a string is always a ConstantArrayType. In C++, the char
/// type is const qualified, in C it is not.
///
/// Note that strings in C can be formed by concatenation of multiple string
/// literal pptokens in translation phase #6. This keeps track of the locations
/// of each of these pieces.
///
/// Strings in C can also be truncated and extended by assigning into arrays,
/// e.g. with constructs like:
/// char X[2] = "foobar";
/// In this case, getByteLength() will return 6, but the string literal will
/// have type "char[2]".
class StringLiteral final
: public Expr,
private llvm::TrailingObjects {
friend class ASTStmtReader;
friend TrailingObjects;
/// StringLiteral is followed by several trailing objects. They are in order:
///
/// * A single unsigned storing the length in characters of this string. The
/// length in bytes is this length times the width of a single character.
/// Always present and stored as a trailing objects because storing it in
/// StringLiteral would increase the size of StringLiteral by sizeof(void *)
/// due to alignment requirements. If you add some data to StringLiteral,
/// consider moving it inside StringLiteral.
///
/// * An array of getNumConcatenated() SourceLocation, one for each of the
/// token this string is made of.
///
/// * An array of getByteLength() char used to store the string data.
public:
enum StringKind { Ascii, Wide, UTF8, UTF16, UTF32 };
private:
unsigned numTrailingObjects(OverloadToken) const { return 1; }
unsigned numTrailingObjects(OverloadToken) const {
return getNumConcatenated();
}
unsigned numTrailingObjects(OverloadToken) const {
return getByteLength();
}
char *getStrDataAsChar() { return getTrailingObjects(); }
const char *getStrDataAsChar() const { return getTrailingObjects(); }
const uint16_t *getStrDataAsUInt16() const {
return reinterpret_cast(getTrailingObjects());
}
const uint32_t *getStrDataAsUInt32() const {
return reinterpret_cast(getTrailingObjects());
}
/// Build a string literal.
StringLiteral(const ASTContext &Ctx, StringRef Str, StringKind Kind,
bool Pascal, QualType Ty, const SourceLocation *Loc,
unsigned NumConcatenated);
/// Build an empty string literal.
StringLiteral(EmptyShell Empty, unsigned NumConcatenated, unsigned Length,
unsigned CharByteWidth);
/// Map a target and string kind to the appropriate character width.
static unsigned mapCharByteWidth(TargetInfo const &Target, StringKind SK);
/// Set one of the string literal token.
void setStrTokenLoc(unsigned TokNum, SourceLocation L) {
assert(TokNum < getNumConcatenated() && "Invalid tok number");
getTrailingObjects()[TokNum] = L;
}
public:
/// This is the "fully general" constructor that allows representation of
/// strings formed from multiple concatenated tokens.
static StringLiteral *Create(const ASTContext &Ctx, StringRef Str,
StringKind Kind, bool Pascal, QualType Ty,
const SourceLocation *Loc,
unsigned NumConcatenated);
/// Simple constructor for string literals made from one token.
static StringLiteral *Create(const ASTContext &Ctx, StringRef Str,
StringKind Kind, bool Pascal, QualType Ty,
SourceLocation Loc) {
return Create(Ctx, Str, Kind, Pascal, Ty, &Loc, 1);
}
/// Construct an empty string literal.
static StringLiteral *CreateEmpty(const ASTContext &Ctx,
unsigned NumConcatenated, unsigned Length,
unsigned CharByteWidth);
StringRef getString() const {
assert(getCharByteWidth() == 1 &&
"This function is used in places that assume strings use char");
return StringRef(getStrDataAsChar(), getByteLength());
}
/// Allow access to clients that need the byte representation, such as
/// ASTWriterStmt::VisitStringLiteral().
StringRef getBytes() const {
// FIXME: StringRef may not be the right type to use as a result for this.
return StringRef(getStrDataAsChar(), getByteLength());
}
void outputString(raw_ostream &OS) const;
uint32_t getCodeUnit(size_t i) const {
assert(i < getLength() && "out of bounds access");
switch (getCharByteWidth()) {
case 1:
return static_cast(getStrDataAsChar()[i]);
case 2:
return getStrDataAsUInt16()[i];
case 4:
return getStrDataAsUInt32()[i];
}
llvm_unreachable("Unsupported character width!");
}
unsigned getByteLength() const { return getCharByteWidth() * getLength(); }
unsigned getLength() const { return *getTrailingObjects(); }
unsigned getCharByteWidth() const { return StringLiteralBits.CharByteWidth; }
StringKind getKind() const {
return static_cast(StringLiteralBits.Kind);
}
bool isAscii() const { return getKind() == Ascii; }
bool isWide() const { return getKind() == Wide; }
bool isUTF8() const { return getKind() == UTF8; }
bool isUTF16() const { return getKind() == UTF16; }
bool isUTF32() const { return getKind() == UTF32; }
bool isPascal() const { return StringLiteralBits.IsPascal; }
bool containsNonAscii() const {
for (auto c : getString())
if (!isASCII(c))
return true;
return false;
}
bool containsNonAsciiOrNull() const {
for (auto c : getString())
if (!isASCII(c) || !c)
return true;
return false;
}
/// getNumConcatenated - Get the number of string literal tokens that were
/// concatenated in translation phase #6 to form this string literal.
unsigned getNumConcatenated() const {
return StringLiteralBits.NumConcatenated;
}
/// Get one of the string literal token.
SourceLocation getStrTokenLoc(unsigned TokNum) const {
assert(TokNum < getNumConcatenated() && "Invalid tok number");
return getTrailingObjects()[TokNum];
}
/// getLocationOfByte - Return a source location that points to the specified
/// byte of this string literal.
///
/// Strings are amazingly complex. They can be formed from multiple tokens
/// and can have escape sequences in them in addition to the usual trigraph
/// and escaped newline business. This routine handles this complexity.
///
SourceLocation
getLocationOfByte(unsigned ByteNo, const SourceManager &SM,
const LangOptions &Features, const TargetInfo &Target,
unsigned *StartToken = nullptr,
unsigned *StartTokenByteOffset = nullptr) const;
typedef const SourceLocation *tokloc_iterator;
tokloc_iterator tokloc_begin() const {
return getTrailingObjects();
}
tokloc_iterator tokloc_end() const {
return getTrailingObjects() + getNumConcatenated();
}
SourceLocation getBeginLoc() const LLVM_READONLY { return *tokloc_begin(); }
SourceLocation getEndLoc() const LLVM_READONLY { return *(tokloc_end() - 1); }
static bool classof(const Stmt *T) {
return T->getStmtClass() == StringLiteralClass;
}
// Iterators
child_range children() {
return child_range(child_iterator(), child_iterator());
}
const_child_range children() const {
return const_child_range(const_child_iterator(), const_child_iterator());
}
};
/// [C99 6.4.2.2] - A predefined identifier such as __func__.
class PredefinedExpr final
: public Expr,
private llvm::TrailingObjects {
friend class ASTStmtReader;
friend TrailingObjects;
// PredefinedExpr is optionally followed by a single trailing
// "Stmt *" for the predefined identifier. It is present if and only if
// hasFunctionName() is true and is always a "StringLiteral *".
public:
enum IdentKind {
Func,
Function,
LFunction, // Same as Function, but as wide string.
FuncDName,
FuncSig,
LFuncSig, // Same as FuncSig, but as as wide string
PrettyFunction,
/// The same as PrettyFunction, except that the
/// 'virtual' keyword is omitted for virtual member functions.
PrettyFunctionNoVirtual
};
private:
PredefinedExpr(SourceLocation L, QualType FNTy, IdentKind IK,
StringLiteral *SL);
explicit PredefinedExpr(EmptyShell Empty, bool HasFunctionName);
/// True if this PredefinedExpr has storage for a function name.
bool hasFunctionName() const { return PredefinedExprBits.HasFunctionName; }
void setFunctionName(StringLiteral *SL) {
assert(hasFunctionName() &&
"This PredefinedExpr has no storage for a function name!");
*getTrailingObjects() = SL;
}
public:
/// Create a PredefinedExpr.
static PredefinedExpr *Create(const ASTContext &Ctx, SourceLocation L,
QualType FNTy, IdentKind IK, StringLiteral *SL);
/// Create an empty PredefinedExpr.
static PredefinedExpr *CreateEmpty(const ASTContext &Ctx,
bool HasFunctionName);
IdentKind getIdentKind() const {
return static_cast