Howdy,
I stumbled over this misbehavior while debugging some problem in
Wireshark. The problem has been reduced to the test case below (a
simplified snippet from the time_secs_to_str_buf() function in
Wireshark):
<<<<<
#include <stdio.h>
void foo(int v)
{
if (v < 0) {
v = -v;
}
if (v < 0) {
fprintf(stderr, "bad number\n");
return;
}
fprintf(stderr, "[%d]\n", v);
}
int main(void)
{
foo(0x80000000);
return 0;
}
<<<<<<
The problem is that with -O2, the second conditional gets optimized
away. However, such optimization results in a misbehavior for the
minimum number representable in 32 bits, 0x80000000. The option which
triggers this optimization is -ftree-vrp.
I would consider this a bug in VRP, since (judging by the description of
the -ftree-vrp option), this option is only supposed to eliminate
equivalent ranges.
Regards,
Alexey.
Best regards,
Alexey Neyman.
