[Bug c/38341] Wrong warning comparison of promoted ~unsigned with unsigned

[michael dot malone at tait dot co dot nz]

------- Comment #8 from michael dot malone at tait dot co dot nz  2009-02-24 
00:40 -------
#ifdef UINT
  #include <stdint.h>
  #define TYPE uint16_t
#else
  #define TYPE unsigned short int
#endif

#define VALUE 0xFF

int main(void);

int main() {
   TYPE variable_a = ~VALUE;
   TYPE variable_b = VALUE;
   TYPE result;

   #ifdef ASSIGN
   TYPE tmp = ~variable_a;
   result = (variable_b == tmp);
   #else
   result = (variable_b == (TYPE) ~variable_a);
   #endif

   return 0;
}

Further to John's input, here is a sample program which shows up why this bug
is interesting.  When one uses a typedef'd type, the promoted comparison
warning is displayed.  When one does not, it isn't!

This is not the case for gcc-4.2.3 -both variants compile without warnings.

The compile commands I used were:
gcc gcc_bug.c -W -Wall -o bug
and
gcc gcc_bug.c -W -Wall -DUINT -o bug


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38341