https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79482
Bug ID: 79482
Summary: _Static_assert(__builtin_constant_p(x)):
Product: gcc
Version: 6.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: mocramis at gmail dot com
Target Milestone: ---
Compiling the wollowing code with gcc -O1 main.c:
===== main.c =====
int main(int argc, char *argv[]) {
int x = 0;
_Static_assert(__builtin_constant_p(x) ? 1 : 2, "error");
return 0;
}
===================
fails with the error :
error: expression in static assertion is not constant
With optimizations disabled (O0), it compiles fine.
Also, if we replace the '?' operator by __builtin_choose_expr, the compiler
seems to behave as expected :
===== main.c =====
int main(int argc, char *argv[]) {
int x = 0;
_Static_assert(__builtin_choose_expr(__builtin_constant_p(x), 1, 2),
"error");
return 0;
}
===================
This compiles fine with any level of optimisation (while __builtin_choose_expr
should expect the same 'constness' as _Static assert).
Clang 3.9 compiles both versions without errors (with O3).
Tested with gcc 6.3.1.
