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

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• 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.

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rS FreeBSD src repository - subversion

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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
42	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
42	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
42	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
42	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
42	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
42	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.