[Bug ipa/108871] attribute nonnull does not spot nullptr O2 and above when function inlined

[jg at jguk dot org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108871

--- Comment #8 from Jonny Grant <jg at jguk dot org> ---
Another test case.

https://godbolt.org/z/qss7jj51x


I noticed when not using -fanalyzer gcc still warns about __builtin_puts being
passed NULL. However gcc doesn't warn about my own function with attribute
nullptr.  Maybe I'm missing something.


With puts() it gives a nice warning

In function 'void f2(const char*)',
    inlined from 'void f1(const char*)' at <source>:22:7,
    inlined from 'int main()' at <source>:28:7:
<source>:11:19: warning: argument 1 null where non-null expected [-Wnonnull]
   11 |     __builtin_puts(str);
      |     ~~~~~~~~~~~~~~^~~~~


// -std=c++23 -O1 -Wnonnull -Wall

// Test case that shows a difference in behavour,
// __builtin_puts generates a warning but not f1()
// Note, not using -fanalyzer

// Change this to 1 to see nonnull warning
#define USE_PUTS 0

void f2(const char * str)
{
#if USE_PUTS
    __builtin_puts(str);
#else
    char a = *str;
    __builtin_printf("%c", a);
#endif
}

void f1(const char * const str) __attribute__ ((nonnull));
void f1(const char * const str)
{

    f2(str);
}

int main()
{
    const char * a = nullptr;
    f1(a);
}