Concurrency: silence some -Wcast-function-type-mismatch warnings
#78911
Conversation
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@swift-ci please test |
The C++ standard does not guarantee that the code and data pointers are interchangeable. Recent enhancements to clang now properly identify the improper `reinterpret_cast` between function types. Silence the warning by switching to `std::bit_cast`. Unfortunately, this is a C++20 feature and we are still on C++17. In the case that the compiler doesn't have a `bit_cast` implementation, fallback with some UB to a local definition.
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@swift-ci please test |
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Thanks for fixing this! There are many of these warnings, beyond what you fixed here, that we've so far ignored with |
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@tshortli happy to do that if you know of a good place to centralise the definition to. I'd rather do that as a follow up though. This at least pulls all the UB into a single location and we are explicit about this as this covers all of Concurrency and I suspect that we will want this across other modules. |
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I don't have a particular place in mind, I'm just making a general observation that it would be nice to not have too many duplicates of this incase someone notices that it needs to be tweaked. Practically speaking, we probably need one copy of the definition per build that does not share any headers. So one for the compiler, one for the runtime, etc. None of this is blocking, I'm happy just to have this solved in a reasonably principled way and I can look into extending this to the places where I previously suppressed warnings instead. |
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Going to merge this for now. I think that I have an idea for a shared location, but that can be done as a follow up. |
The C++ standard does not guarantee that the code and data pointers are interchangeable. Recent enhancements to clang now properly identify the improper
reinterpret_castbetween function types. Silence the warning by switching tostd::bit_cast. Unfortunately, this is a C++20 feature and we are still on C++17. In the case that the compiler doesn't have abit_castimplementation, fallback with some UB to a local definition.