https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113514
Bug ID: 113514
Summary: Wrong __builtin_dynamic_object_size when using a set
local variable
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: isanbard at gmail dot com
Target Milestone: ---
There appears to be an issue with __builtin_dynamic_object_size() when using a
local variable. The following code should output 40 for each __bdos call:
$ cat test.c
#include <stdio.h>
struct s {
int a, b, c, d;
int foo;
#define IDX 2
int blue;
char bar[IDX][40];
int baz;
int qux;
};
int main(int argc, char **argv) {
struct s f;
#define report(x) fprintf(stderr, #x ": %zu\n", x)
report(__builtin_dynamic_object_size(f.bar[1], 1));
report(__builtin_dynamic_object_size(f.bar[1], 3));
report(__builtin_dynamic_object_size(f.bar[argc], 1));
report(__builtin_dynamic_object_size(f.bar[argc], 3));
argc = 1;
report(__builtin_dynamic_object_size(f.bar[argc], 1));
report(__builtin_dynamic_object_size(f.bar[argc], 3));
return 0;
}
However, the last two print 48:
$ gcc -O2 test.c && a.out
__builtin_dynamic_object_size(f.bar[1], 1): 40
__builtin_dynamic_object_size(f.bar[1], 3): 40
__builtin_dynamic_object_size(f.bar[argc], 1): 40
__builtin_dynamic_object_size(f.bar[argc], 3): 40
__builtin_dynamic_object_size(f.bar[argc], 1): 48
__builtin_dynamic_object_size(f.bar[argc], 3): 48
