[libcxx-commits] [libcxx] [libc++][AIX] Marking the tests UNSUPPORTED as the current implementation of fopen w+bx overrides ios::noreplace (PR #188425)

[David Tenty via libcxx-commits]

https://github.com/daltenty requested changes to this pull request.

I'm not convinced that marking this unsupported is the correct direction here. The underlying issue is this test expects behaviour that the specification does not mandate. 

`ios::noreplace` is mapped to as-if you called `fopen` with 'x'`. The C23 standard say for this mode:
```
If the implementation is not capable of performing the check for the existence of the file and the
creation of the file atomically, it shall fail instead of performing a non-atomic check and creation
```

So I think the test should be modified to expect that result as valid on some platforms (i.e. AIX)

https://github.com/llvm/llvm-project/pull/188425