| Issue |
74240
|
| Summary |
Wrong code at -O2/3 since `clang-14.0.0`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
jun-wei-zeng
|
Compiler explorer: https://godbolt.org/z/97Yv6dEa7
I compiled the following code with `clang-15.0.0 and above version` at `-O2/3`, and the program output `nothing` and return `48`. And when I compiled with `clang-14.0.0` at `-O2/3`, and the program output `1` and return `0`.
So, this bug exists in `clang-14.0.0 and above version`.
If the code is compiled correctly, the execution should output `nothing` and return `0`.
```c
$ cat test.c
int printf(const char*, ...);
union a {
int d, b[4];
};
int main() {
union a c = {0};
int d = 0;
for (; d < 4; ++d)
if (c.b[d])
printf("1\n");
}
$
$ clang-16.0.0 -O1 test.c; ./a.out
$ echo $?
0
$
$ clang-16.0.0 -O2 test.c; ./a.out
$ echo $?
48
$
$ clang-16.0.0 -O3 test.c; ./a.out
$ echo $?
48
$
$ clang-14.0.0 -O2 test.c; ./a.out
1
$ echo $?
0
$
$ clang-16.0.0 --version
clang version 16.0.0
Target: x86_64-unknown-linux-gnu
Thread model: posix
$
$ clang-14.0.0 --version
clang version 14.0.0
Target: x86_64-unknown-linux-gnu
Thread model: posix
```
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