C99 7.18.4.1 (as revised by ISO/IEC 9899:1999/Cor.1:2001) says that
UINT8_C and UINT16_C return values corresponding to uint_least8_t and
uint_least16_t.  They therefore must promote the same way.  But glibc
appends 'U', which causes UINT8_C and UINT16_C to promote to 'unsigned
int', not 'int'.  Here is a test program illustrating the bug: it
strictly conforms to the C99 but GCC + glibc reject it.  I'll attach
the obvious patch.

#include <stdint.h>
char test1[(-1 < UINT8_C (0)) == (-1 < (uint_least8_t) 0) ? 1 : -1];
char test2[(-1 < UINT16_C (0)) == (-1 < (uint_least16_t) 0) ? 1 : -1];

------- Additional Comment #1 From Paul Eggert 2006-06-24 06:36 -------

Created an attachment (id=1121)
UINT8_C and UINT16_C should not append U

------- Additional Comment #2 From Ulrich Drepper 2006-08-12 21:23 -------

The specificaiton is broken one way or another so I don't really care.  The
patch is in cvs.