https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108871
--- Comment #4 from Jonny Grant <jg at jguk dot org> --- (In reply to Andrew Pinski from comment #3) > *** Bug 108893 has been marked as a duplicate of this bug. *** Hello Andrew May I check, I thought attribute access read_only was different from attribute nonnull? https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html "Note that the access attribute merely specifies how an object referenced by the pointer argument can be accessed; it does not imply that an access will happen. Also, the access attribute does not imply the attribute nonnull; it may be appropriate to add both attributes at the declaration of a function that unconditionally manipulates a buffer via a pointer argument. See the nonnull attribute for more information and caveats." Seems to be stating, nonnull is not the same as access read_only. Or am I missing something? I had understood __attribute__((access(read_only, 1))); would be enough on a -O3 -Wall build to generate a warning that a nullptr had been passed (even if it was not actually dereferenced) Here is an example that actually does derefernence, and runtime SEGV, but it the access read_only itself doesn't give any build warning. Just an example, I'm only hoping to get build warnings when optimizer sees that nullptr got through g++ -std=c++23 -O3 -Wall https://godbolt.org/z/KbzcjEjYj void f(const char * const str) __attribute__((access(read_only,1))); void f(const char * const str) { if(*str == 'a') { __builtin_puts("a1"); } else { __builtin_puts("a2"); } } int main() { const char * a = nullptr; f(a); }
