Clang 14.x ornery about std::experimental::coroutine_traits about qcoro HOT 3 CLOSED

std::experimental isn't used if the standard library defines __cpp_lib_coroutine, thus I suspect something is fishy with clang/libc++ in Android NDK...I downloaded the Android NDK 25 (I downloaded 25.2.9519653, which is slightly newer than yours, but that shouldn't matter), and searching the NDK I can only find the <experimental/coroutine> header:

❯ cd android-ndk-r25c
❯ find . -name "coroutine"
./toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/experimental/coroutine
./sources/cxx-stl/llvm-libc++/include/experimental/coroutine

The reason why is most likely because the Android NDK ships clang 14, but the libc++ standard library is older:

❯ cat toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/__libcpp_version
11000

libc++ 11 indeed does not have the <coroutines> include header, only <experimental/coroutines>, so QCoro falls back to including that, which triggers the warning from clang.

I'll add the compile option to QCoro when building on Android....

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Btw I also checked NDK 26, which ships libc++ 17 which does have full coroutine support, so QCoro should work there out of the box without any changes.

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Your attention to detail is remarkable. Thank you!

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