https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112486
Bug ID: 112486
Summary: GCC: 14: hangs with always_inline
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: 141242068 at smail dot nju.edu.cn
Target Milestone: ---
Compiler Explorer: https://gcc.godbolt.org/z/3n34j7fPT
When try to compile this program with `gcc-14 -O2`:
```
unsigned long flg = 0;
int n_1 = {0};
__attribute__((always_inline))
long sub(unsigned long n) {
int a, b;
if (n_1 >= 2) {
if (n_1 % 2 == 0) {
a = sub(n_1 / 2);
{ return (a & 2 >> sub(n_1 / 2 - 1)) * a; };
} else {
a = sub(n_1 / 2 + 1);
b = sub(n_1 / 2);
return (sub(n_1 / 2)) * a + b * b;
}
} else
return (long)n_1;
}
int main(void) {
if (sub(30) != 832040L) flg |= 0x100L;
if (flg) abort();
exit(0);
}
```
GCC 14 hangs with a lot of output, according to the output, it seems GCC tries
to recursively expand all invocation to `sub`.
The partial output pasted from compiler explorer:
```
In function 'sub',
inlined from 'sub' at <source>:13:11,
inlined from 'sub' at <source>:12:11,
inlined from 'sub' at <source>:13:11,
inlined from 'sub' at <source>:10:26,
inlined from 'sub' at <source>:10:26,
inlined from 'sub' at <source>:10:26,
inlined from 'sub' at <source>:10:26,
inlined from 'sub' at <source>:9:11,
inlined from 'sub' at <source>:9:11,
inlined from 'sub' at <source>:12:11,
inlined from 'sub' at <source>:12:11,
inlined from 'main' at <source>:21:7:
<source>:5:6: error: inlining failed in call to 'always_inline' 'sub':
recursive inlining
5 | long sub(unsigned long n) {
| ^~~
<source>:10:26: note: called from here
10 | { return (a & 2 >> sub(n_1 / 2 - 1)) * a; };
| ^~~~~~~~~~~~~~~~
<source>:5:6: error: inlining failed in call to 'always_inline' 'sub':
recursive inlining
5 | long sub(unsigned long n) {
| ^~~
<source>:9:11: note: called from here
9 | a = sub(n_1 / 2);
| ^~~~~~~~~~~~
<source>:5:6: error: inlining failed in call to 'always_inline' 'sub':
recursive inlining
5 | long sub(unsigned long n) {
| ^~~
<source>:13:11: note: called from here
13 | b = sub(n_1 / 2);
| ^~~~~~~~~~~~
<source>:5:6: error: inlining failed in call to 'always_inline' 'sub':
recursive inlining
5 | long sub(unsigned long n) {
| ^~~
<source>:12:11: note: called from here
12 | a = sub(n_1 / 2 + 1);
| ^~~~~~~~~~~~~~~~
In function 'sub',
inlined from 'sub' at <source>:13:11,
inlined from 'sub' at <source>:13:11,
inlined from 'sub' at <source>:10:26,
inlined from 'sub'
[Truncated]
Compiler returned: 143
```
