https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103887
Bug ID: 103887
Summary: -fsanitize=shift affects constness of an expression
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: m...@mk-sys.cz
Target Milestone: ---
This simplified testcase
---------------------------------------------------------------------------
#include <stdint.h>
#define ASSERT_ON_COMPILE_SELECTOR_SIZE(e) \
_Static_assert(((__builtin_constant_p(e) && ((e) >> 16) == 0)) || \
(sizeof(e) <= 2), "problem")
int f(uint16_t tr)
{
ASSERT_ON_COMPILE_SELECTOR_SIZE(tr);
return 0;
}
---------------------------------------------------------------------------
builds cleanly with "-O2" but fails with "-O2 -fsanitize=shift":
---------------------------------------------------------------------------
mike@lion:/tmp/gcc> gcc-11 -Wall -Wextra -O2 -c foo.c
mike@lion:/tmp/gcc> gcc-11 -Wall -Wextra -O2 -fsanitize=shift -c foo.c
foo.c: In function ‘f’:
foo.c:4:72: error: expression in static assertion is not constant
4 | _Static_assert(((__builtin_constant_p(e) && ((e) >> 16) == 0))
|| \
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
5 | (sizeof(e) <= 2), "problem")
| ~~~~~~~~~~~~~~~~
foo.c:9:9: note: in expansion of macro ‘ASSERT_ON_COMPILE_SELECTOR_SIZE’
9 | ASSERT_ON_COMPILE_SELECTOR_SIZE(tr);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---------------------------------------------------------------------------
I was able to reproduce the same with various gcc version from gcc7 to gcc12.
