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[Concurrency] Use reinterpret_cast for function_cast when ptrauth is on. #81380

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May 9, 2025
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[Concurrency] Use reinterpret_cast for function_cast when ptrauth is on. #81380

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8 changes: 8 additions & 0 deletions include/swift/Basic/Casting.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,9 +41,17 @@ Destination function_cast(Source source) {
static_assert(std::is_trivially_copyable_v<Destination>,
"The destination type must be trivially constructible");

#if __has_feature(ptrauth_calls)
// Use reinterpret_cast here so we perform any necessary auth-and-sign.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcast-function-type-mismatch"
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I don't think that we should be silencing away this warning. This is technically UB, and the compiler is pointing that out.

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I don’t see any use in leaving it. The cast is necessary for correct behavior when ptrauth_calls is on, so we’d just have a warning we can’t address.

return reinterpret_cast<Destination>(source);
#pragma clang diagnostic pop
#else
Destination destination;
memcpy(&destination, &source, sizeof(source));
return destination;
#endif
}

}
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