linuxkpi: Add overflow.h
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Authored by manu on May 26 2020, 10:57 AM.

Details

Reviewers

• hselasky
emaste

Commits

rS363791: MFC r361549:
rS363789: MFC r361549:
rS361549: linuxkpi: Add overflow.h

Summary

Only add check_add_overflow and check_mul_overflow as those are the only
two needed function by DRM v5.3.
Since both gcc and clang have builtin to do this check, use them directly.

Diff Detail

Repository

rS FreeBSD src repository - subversion

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

manu created this revision.May 26 2020, 10:57 AM

Herald added a subscriber: imp. · View Herald TranscriptMay 26 2020, 10:57 AM

manu requested review of this revision.May 26 2020, 10:57 AM

Should there be an ifdef for LINT builds?

In D25015#550743, @hselasky wrote:

Should there be an ifdef for LINT builds?

What do you mean ?

Have a look at: sys/cdefs.h

--HPS

You might want to ifdef the use of __builting for compilers not supporting it like done in sys/cdefs.h --- OK ?

Only add the macros if the compiler have the builtin.
Old compiler aren't supported.

• hselasky added inline comments.May 27 2020, 8:35 AM

sys/compat/linuxkpi/common/include/linux/overflow.h
41 ↗	(On Diff #72305)	Should there be an #else case here?

manu added inline comments.May 27 2020, 8:40 AM

sys/compat/linuxkpi/common/include/linux/overflow.h
41 ↗	(On Diff #72305)	As said in the comment old compilers aren't supported. Do you think it's really necessary to support compilers that don't have this builtin ? I'll check when they appeared on each one.

• hselasky added inline comments.May 27 2020, 8:45 AM

sys/compat/linuxkpi/common/include/linux/overflow.h
41 ↗	(On Diff #72305)	It might not be an old compiler but a code checker. Make sure there is an else case there. Thank you!

manu added inline comments.May 27 2020, 8:50 AM

sys/compat/linuxkpi/common/include/linux/overflow.h
41 ↗	(On Diff #72305)	And just #define check_mul_overflow(a, b, c) (0) ? Or #error ? What do you prefer ?

• hselasky added inline comments.May 27 2020, 9:13 AM

sys/compat/linuxkpi/common/include/linux/overflow.h
41 ↗	(On Diff #72305)	I think we need to use #error "Missing support for check_mul_overflow()."

Add #error if the compiler doesn't have the required builtin.

manu added inline comments.May 27 2020, 9:19 AM

sys/compat/linuxkpi/common/include/linux/overflow.h
41 ↗	(On Diff #72305)	I've added some error but logging the missing builtin name so the users compiling stuff doesn't have to look up this file to see what the problem is.