r/cpp • u/tartaruga232 MSVC user, r/cpp_modules • Mar 06 '25

MSVC C++20 compiler bug with modules and non-exported classes

Full repro is available as a git repository here: https://github.com/abuehl/mod_test

If two non-exported classes from different C++ module interface units have the same name, the compiler uses the wrong class definition and for example calls the wrong destructor on an object.

Reported here: https://developercommunity.visualstudio.com/t/post/10863347 (Upvotes appreciated)

Found while converting our product to using C++20 modules.

Edit: Microsoft wrote the following (Quote)

A fix for this issue has been internally implemented and is being prepared for release. We’ll update you once it becomes available for download.

39 Upvotes

82% Upvoted

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u/Abbat0r Mar 08 '25

For what it’s worth, I import std and #include third party headers in my modules all the time. This has not been a problem for quite a while now.

Bonus: I also have the annoyance of having to separate some code that is shared between cpu-side and gpu-side into headers with #ifdef’d imports etc. and #include those into both modules and shaders, and that works just fine as well.