http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53986
--- Comment #5 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-05
11:35:40 UTC ---
Just to illustrate:
$ cat t.c
#include <stdio.h>
int
main (void)
{
int cases[] = { -16, -12, -9, -17 };
int i, v;
printf ("Show why cast must happen after add. T==1 iff (D.1732_8 != 0)\n");
printf ("%-12s%-12s%-12s%-12s\t T T\n",
"s_1", "(u)s_1", "s_1+16", "((u)s_1)+16");
for (i = 0; i < 4; i++)
{
int v = cases[i];
unsigned int uv = (unsigned) v;
printf ("%-12d%-12u%-12d%-12u\t%2d%2d\n",
v, uv, v+16, uv+16,
(v+16) > 7, (uv+16) > 7);
}
return 0;
}
$ gcc t.c
$ ./a.out
Show why cast must happen after add. T==1 iff (D.1732_8 != 0)
s_1 (u)s_1 s_1+16 ((u)s_1)+16 T T
-16 4294967280 0 0 0 0
-12 4294967284 4 4 0 0
-9 4294967287 7 7 0 0
-17 4294967279 -1 4294967295 0 1
$
