http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55040
Bug #: 55040
Summary: dereferencing type-punned pointer
Classification: Unclassified
Product: gcc
Version: 4.7.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: [email protected]
ReportedBy: [email protected]
Compiling
root@home:~ # cat strict-aliasing.c
#include <stdio.h>
#include <string.h>
int main() {
char x[10];
float y = 1.28;
float *z = (float*)x;
memcpy(x, &y, sizeof(float));
printf("%f\n", *(float*)x);
printf("%f\n", *z);
return 0;
}
with gcc -O2 -Wall strict-aliasing.c -o strict-aliasing
prints:
strict-aliasing.c: In function ‘main’:
strict-aliasing.c:9:3: warning: dereferencing type-punned pointer will break
strict-aliasing rules [-Wstrict-aliasing]
which is a warning for the first printf, but not for the second printf.
According to my understanding, there is no difference between the first and
second printf, so there shall be even number of warnings.
