Fix fstream.seekp(0, ios::cur)

[achabense]

Fixes #3572. As discovered in the issue, we need fseek for side effects even when (off,way)==(0,ios::cur).

[strega-nil-ms]

This seems reasonable to me.

[CaseyCarter]

The fix looks fine, but I'd like to see a regression test (a test that fails without the fix but succeeds with it) to validate it.

[achabense]

I have no idea how to deal with this formatting problem... horrible experience

[StephanTLavavej]

Please note that we strongly recommend configuring your editor to clang-format on save. (VSCode can do this with Microsoft's C/C++ Extension or xaver's clang-format extension, among others.) The CI system is a shared resource, so it's best to avoid putting unnecessary load on it.

[StephanTLavavej]

Thanks for fixing this bug and testing the fix! 😻 I validated and pushed minor cleanups to the test.

[CaseyCarter]

Please note that we strongly recommend configuring your editor to clang-format on save.

There's also a cmake format target that clang-formats everything, but format-on-save is both impossible to forget and (generally) faster since the cmake target literally clang-formats everything.

[CaseyCarter]

I'll push a change to run the test in C++14 mode.

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[StephanTLavavej]

Thanks again for this correctness fix! 🐞 ✅ 💯