https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109581
Bug ID: 109581
Summary: Comparing with -HUGE_VAL wrong result
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: daschuer at mixxx dot org
Target Milestone: ---
Comparing with -HUGE_VAL gives the wrong result with gcc (GCC) 13.0.1 20230401
(Red Hat 13.0.1-0).
GCC 12.2 is and clang are not effected.
This bug breaks Mixxx after compiling it on openSUSE Tumbleweed and Fedora 38
https://github.com/mixxxdj/mixxx/issues/11483
The workaround is to store -HUGE_VAL as a volatile first.
This is a minimal code that demonstrates the issue:
#include <stdio.h>
#include <math.h>
int main(int num) {
long long rawInf = 0xfff0000000000000;
volatile double inf = *(double*)(void*)&rawInf;
if (inf == -HUGE_VAL) {
puts("Success");
} else {
puts("Error");
}
return 0;
}
The following flags are used:
-g -pipe -O3 -ffast-math -funroll-loops -fomit-frame-pointer -mtune=generic
-Wall -Wextra -Wfloat-conversion -Werror=return-type
Result
GCC 12.2 and lower "Success"
GCC 13.0 "Error"
Details: https://godbolt.org/z/7bnb77hv4
