[Bug 58465] New: Wide string misbehavior on C++20 mode vs C++17 mode

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=58465

Bug ID: 58465
           Summary: Wide string misbehavior on C++20 mode vs C++17 mode
           Product: Wine
           Version: 10.11
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: winelib
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 78920
  --> http://bugs.winehq.org/attachment.cgi?id=78920
Simple Winelib program to demonstate the bug (wine_test.cpp) + build/run script
(wine_test.sh) + my test results (output.txt)

When I compile a Winelib application using the `--std=c++20` wineg++ flag
instead of `--std=c++17`, I experience unexpected differences in behavior when
using `std::wstring`. And in both C++ modes the behavior is incorrect.

For example, when I call the `c_str()` method on `std::wstring` and pass the
returned wide C-string to `std::wcslen`, I get different results depending on
whether the Winelib application was compiled in C++20 mode vs C++17 mode. And
in both cases, the reported string length is incorrect.

Also, the distance between the `begin()` and `end()` iterators is different
between C++ modes, and so is the return value of the `length()` method. And all
of the results are incorrect in general.

I originally noticed these `std::wstring` problems here:
https://github.com/LMMS/lmms/pull/7624#issuecomment-2923573719

I've attached a simple Winelib program that demonstrates the bug to this bug
report.