https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108935
Bug ID: 108935
Summary: Incorrect warning for infinite recursion
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: zach-gcc at cs dot stanford.edu
Target Milestone: ---
The following code does not have infinite recursion:
```
typedef struct {
unsigned idx;
int vals[512];
} foo_t;
int ended(foo_t* f) {
return f->idx >= 512;
}
unsigned foo(foo_t* f) {
if (ended(f)) {
return f->idx;
}
do {
f->idx++;
} while(!ended(f) && !f->vals[f->idx]);
return foo(f);
}
```
but -fanalyzer reports infinite recursion (called with `gcc -fanalyzer -c
test.c`). The function always makes progress towards f->idx reaching 512, which
is the termination condition. It is bounded to at most 512 recursive calls. I
can even add `f->idx += 1000` and the warning is still reported.
I've also noticed the following example causes a similar warning, but only when
`foo` is also invoked.
```
typedef struct {
unsigned done;
} foo_t;
unsigned foo(foo_t* f) {
if (f->done) {
return f->done;
}
f->done = 1;
return foo(f);
}
int main() {
foo_t f = (foo_t){
.done = 0,
};
// must be called to cause warning
foo(&f);
}
```
Tested on version GCC 13 20230203 (commit hash a37a0cb303d). Thanks.
