Fix heap-use-after-free for _HAS_EXCEPTIONS=0

[wolframw]

Fixes #5276.

[wolframw]

@microsoft-github-policy-service agree

[A. Jiang (frederick-vs-ja)]

Can we delete (= delete;) the ctors from string when _HAS_EXCEPTIONS = 0? Stephan T. Lavavej (@StephanTLavavej) wolframw

[Stephan T. Lavavej (StephanTLavavej)]

We do have some precedent of outright =deleteing Standard APIs when compiler options make them literally unimplementable (e.g. dynamic_pointer_cast is deleted under /GR-).

In this case, because the option is ancient and the affected constructors (e.g. system_error) are old, I think that's a bit risky. Yes, we're dropping the string information on the floor, but we're preserving the type information in the string literal being stored. That seems like a "best effort" thing to do, and is strictly less problematic for users than the status quo.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks for fixing this surprisingly long-standing correctness bug! 😻 I pushed some test changes, and double-checked that the product code changes are complete.

Note for the future: we recommend against force-pushing after code review has begun, because GitHub makes it harder to see what's changed.

We merge PRs simultaneously to GitHub and our MSVC-internal repo in a semi-manual process, batched up to save time. Your PR will be part of the next batch, possibly this week but more likely next week depending on how busy I am. I'll post comments here as I prepare your PR for merging!

[wolframw]

Stephan T. Lavavej (@StephanTLavavej) Thanks for giving it the finishing touch!

[Stephan T. Lavavej (StephanTLavavej)]

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

[Stephan T. Lavavej (StephanTLavavej)]

Thanks for fixing this bug and congratulations on your first microsoft/STL commit! 💚 😻 🎉