[Bug c/94196] Multiple issues with attributes

[nate at thatsmathematics dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94196

Nate Eldredge <nate at thatsmathematics dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nate at thatsmathematics dot 
com

--- Comment #2 from Nate Eldredge <nate at thatsmathematics dot com> ---
Another case is that the pure attribute is not respected on a function pointer,
though the related const attribute is.

For example:

#include <stdio.h>

int __attribute__((pure,noipa)) my_pure_func(int x) {
    printf("pure func called with %d\n", x);
    return x;
}

int __attribute__((const,noipa)) my_const_func(int x) {
    printf("const func called with %d\n", x);
    return x;
}

int __attribute__((pure)) (*pure_ptr)(int) = my_pure_func;
int __attribute__((const)) (*const_ptr)(int) = my_const_func;

int a,b,c,d;

void foo(void) {
    a = pure_ptr(1) + pure_ptr(1);
    b = my_pure_func(2) + my_pure_func(2);
    c = const_ptr(3) + const_ptr(3);
    d = my_const_func(4) + my_const_func(4);
}

int main(void) {
    foo();
    return 0;
}


gives a warning:

pure.c:13:1: warning: ‘pure’ attribute ignored [-Wattributes]
   13 | int __attribute__((pure)) (*pure_ptr)(int) = my_pure_func;
      | ^~~

and indeed `my_pure_func(1)` is called twice.  The others are handled correctly
and only called once.