Compiling Android project with C++20 and Qt 6.5.8

hamer

Hi,

I have a Qt project which uses c++20 features ("numers", "source_location", etc.) which I want to compile with Qt 6.5.8 for Android but this always fails (using NDK 25.x). The same project works fine with Qt 6.8.1 for Android or Qt 6.5.8 for iOS/Windows.

Is Qt 6.5.8 for Android not compatible with C++20?

Regards,

jsulm

@hamer said in Compiling Android project with C++20 and Qt 6.5.8:

Is Qt 6.5.8 for Android not compatible with C++20?

I don't think so.
What errors do you get?

hamer

It fails with

Fatal error: 'numbers' file not found #include <numbers>

hamer

When I set ANDROID_NDK to "28.0.12916984" then I get errors like these:

In file included from C:/Android/ndk/28.0.12916984/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/include/c++/v1/optional:180:
In file included from C:/Android/ndk/28.0.12916984/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/include/c++/v1/__assert:13:
In file included from C:/Android/ndk/28.0.12916984/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/include/c++/v1/__assertion_handler:14:
C:/Android/ndk/28.0.12916984/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/include/c++/v1/__verbose_abort:20:1: error: expected expression
C:/Android/ndk/28.0.12916984/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/include/c++/v1/__config:866:32: note: expanded from macro '_LIBCPP_BEGIN_NAMESPACE_STD'
                               inline namespace _LIBCPP_ABI_NAMESPACE {
                               ^

But it seems as if NDK 25 and 28 are mixed (although I have set ANDROID_NDK and CMAKE_TOOLCHAIN_FILE to NDK 28).

jsulm

@hamer said in Compiling Android project with C++20 and Qt 6.5.8:

<numbers>

This requires C++20 - did you enable C++20?

hamer

Yes. The project with its C++20 features works on others systems, as well as Qt 6.8.1 for Android but fails with 6.5.x. I cannot use Qt 6.8.1 because there is has a bug which has been fixed in Qt 6.8.2.

jsulm

@hamer But did you verify that C++20 is enabled when you build with 6.5.x? You should enabled it explicitly.

hamer

How can I verify it? My CMakeLists.txt has these lines:

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

jsulm

@hamer said in Compiling Android project with C++20 and Qt 6.5.8:

How can I verify it?

By looking at the build log to see what parameter were passed to the compiler.

hamer

The logs show c++20:

C:/QtCommercial/6.5.8/android_arm64_v8a/include -isystem C:/QtCommercial/6.5.8/android_arm64_v8a/include/QtCore -isystem C:/QtCommercial/6.5.8/android_arm64_v8a/mkspecs/android-clang -isystem C:/QtCommercial/6.5.8/android_arm64_v8a/include/QtGui -isystem C:/QtCommercial/6.5.8/android_arm64_v8a/include/QtNetwork -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fexceptions -frtti -stdlib=libc++ -O3 -DNDEBUG -std=c++20 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -fno-rtti -Wall -Wshadow -Wextra -Wno-error=tautological-constant-compare -pthread

jsulm

@hamer Where is this numbers header included?