https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92326
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|REOPENED |RESOLVED
--- Comment #10 from Martin Sebor <msebor at gcc dot gnu.org> ---
This bug isn't about whether or not a warning is issued but about the format of
the flexible array member printed by it: it should be 'int[]' but was 'int[0]'.
(That's why Jeff and I have been wondering what you meant.)
The warning in the test case in comment #9 is justified: the flexible array has
no elements because struct a is defined but doesn't initialize it with any
(there would be no warning if the struct were only declared but not defined).
Hopefully this test case will explain it:
$ cat pr92326.c && gcc -O2 -S -Wall pr92326.c
struct A a; // a.flexible has no elements
int c, d;
struct A {
int scalar;
int flexible[];
};
void g() {
a.flexible[c] = d; // out-of-bounds regardless of c
}
struct A a2 = { 1, { 0 } }; // b.flexible has 1 element
void g2 (void) {
a2.flexible[c] = d; // out-of-bounds only if c != 0 (probably should warn)
}
extern struct A a3; // b.flexible might have one or more elements
void g3 (void) {
a3.flexible[c] = d; // unknown if it's in-bounds or out-of-bounds
}
pr92326.c: In function ‘g’:
pr92326.c:11:13: warning: array subscript <unknown> is outside array bounds of
‘int[]’ [-Warray-bounds]
11 | a.flexible[c] = d; // out-of-bounds regardless of c
| ~~~~~~~~~~^~~
pr92326.c:7:7: note: while referencing ‘flexible’
7 | int flexible[];
| ^~~~~~~~
pr92326.c:1:10: note: defined here ‘a’
1 | struct A a; // a.flexible has no elements
| ^
