clike: Unset _FORTIFY_SOURCE together with -O0 #14418
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If -O2, -D_FORTIFY_SOURCE=2 and -Werror are present in, e.g., the environment's CFLAGS, then configuration tests that run the compiler will fail unexpectedly due to the use of -O0 (from get_no_optimization_args()), which is not compatible with -D_FORTIFY_SOURCE=2. To overcome this potential problem, provide -U_FORTIFY_SOURCE along with -O0. Fixes: mesonbuild#14417
eli-schwartz
requested changes
Mar 27, 2025
| @@ -171,7 +171,7 @@ def get_compile_only_args(self) -> T.List[str]: | |||
| return ['-c'] | |||
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|
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| def get_no_optimization_args(self) -> T.List[str]: | |||
| return ['-O0'] | |||
| return ['-O0', '-U_FORTIFY_SOURCE'] | |||
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Won't this totally break projects that are performing checks using -D_FORTIFY_SOURCE=XX?
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They would already be broken due to Meson adding -O0. You cannot have -D_FORTIFY_SOURCE=X (where X > 0) together with -O0. The code in features.h that produces the warning looks like:
#if defined _FORTIFY_SOURCE && _FORTIFY_SOURCE > 0
# if !defined __OPTIMIZE__ || __OPTIMIZE__ <= 0
# warning _FORTIFY_SOURCE requires compiling with optimization (-O)
# elif !__GNUC_PREREQ (4, 1)
...
# endif
#endif
#ifndef __USE_FORTIFY_LEVEL
# define __USE_FORTIFY_LEVEL 0
#endif
i.e., if _FORTIFY_SOURCE is defined and has a value greater than zero and you add -O0 to the compiler switches, you will get the warning and the effective fortification level used (__USE_FORTIFY_LEVEL) will be 0.
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If -O2, -D_FORTIFY_SOURCE=2 and -Werror are present in, e.g., the environment's CFLAGS, then configuration tests that run the compiler will fail unexpectedly due to the use of -O0 (from get_no_optimization_args()), which is not compatible with -D_FORTIFY_SOURCE=2. To overcome this potential problem, provide -U_FORTIFY_SOURCE along with -O0.
Fixes: #14417