https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71598
Bug ID: 71598
Summary: Wrong optimization with aliasing enums
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ch3root at openwall dot com
Target Milestone: ---
Source code:
----------------------------------------------------------------------
extern void abort (void);
enum e1 { c1 };
enum e2 { c2 };
__attribute__((noinline,noclone))
int f(enum e1 *p, enum e2 *q)
{
*p = 1;
*q = 2;
return *p;
}
int main()
{
unsigned x;
if (f(&x, &x) != 2)
abort();
}
----------------------------------------------------------------------
Results:
----------------------------------------------------------------------
$ gcc -std=c11 -pedantic -Wall -Wextra -O3 test.c && ./a.out
Aborted
----------------------------------------------------------------------
gcc version: gcc (GCC) 7.0.0 20160616 (experimental)
In gcc such enums are compatible with unsigned int. Hence they could alias. But
gcc seem to (wrongly) assume that *p and *q cannot refer to the same object.
