https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125973
Bug ID: 125973
Summary: Inconsistent handling of static compound literals
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: luigighiron at gmail dot com
Target Milestone: ---
GCC produces a surprising result with the following program:
#include<stdio.h>
int main(){
for(unsigned u=0;u<5;++u){
static bool b={};
static int i={};
printf("%i %i %i %i\n",--(static bool){},--b,--(static int){},--i);
}
}
The result is:
1 1 -1 -1
1 0 -2 -2
1 1 -3 -3
1 0 -4 -4
1 1 -5 -5
It appears that (static bool){} gets reinitialized each loop iteration, but
(static int){} does not. This difference is surely not intended, and not
reinitializing appears to be the correct result:
> Otherwise, if the storage duration is automatic, the initializer is evaluated
> at each evaluation of the compound literal; if the storage duration is static
> or thread the initializer is (as if) evaluated once prior to program startup.
Section 6.5.3.6 "Compound literals" Paragraph 7 ISO/IEC 9899:2024
Enumerated types compatible with bool appear to have the same issue, and
putting the object inside of a structure type appears to remove the issue.
Also, PR18814 looks to be invalid given this wording. The initializers of
compound literals which designate objects with automatic storage duration get
evaluated each time, just as with ordinary declarations and those cause
reinitialization to happen.
