Got compile error when build Qt 6.7.2 for Android

[ytexas]

Hi everyone,

I'm trying build qt for android with the doc android-building. But got a build error may need your help

My environment is Archlinux. I used to success built a qt application for android by qt5 (years ago). And recently I'd like to trying build qt 6.7.2 for android.

I installed android sdk and ndk by sdk manager. According to the doc. I have done the host building and installed host tools by:

cd qt6.7.2-host
mkdir build
cd build
cmake .. -G Ninja -DFEATURE_developer_build=ON -DCMAKE_INSTALL_PREFIX=~/Qt/6.7.2-host
cmake --build . --parallel
cmake --install .

But got compile error when trying to build qt for andorid with following commands:

cd qt6.7.2-android
mkdir build
cd build
cmake ..  -G Ninja -DCMAKE_BUILD_TYPE=Release  \ 
  -DQT_HOST_PATH=~/Qt/6.7.2-host \
  -DCMAKE_INSTALL_PREFIX=~/Qt/6.7.2-android \
  -DCMAKE_ANDROID_ARCH_ABI=x86_64 \
  -DANDROID_SDK_ROOT=~/Android/sdk \
  -DANDROID_NDK=~/Android/Sdk/ndk/27.0.12077973

# and got compile error here
cmake --build . --parallel 

And got compile error message:

Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/__utility/declval.h:31:17: error: static assertion failed due to requirement '!__is_same(float, float)': std::declval can only be used in an unevaluated context. It's likely that your current usage is trying to extract a value from the function.
   31 |   static_assert(!__is_same(_Tp, _Tp),
      |                 ^~~~~~~~~~~~~~~~~~~~
qt6.7.2-android/qtbase/src/corelib/kernel/qjnitypes.h:130:26: note: in instantiation of function template specialization 'std::declval<float>' requested here
  130 |     return function(std::declval<Args>()...);
      |                          ^

So my question is:

• what dose this compile error means?
• is there some configuration or steps I missed?
• how to fix this compile error to build a qt 6.7.2 for andorid?

Thanks!

[mvuori]

I don't know anything about this, but as the same code has compiled for developers at Qt using an older NDK, I'd suspect its compiler, and would try downgrading the NDK.

[ytexas]

@mvuori Thanks for reply,

I have tried downgraded NDK version, from 26.x to 22.x, event the 26.1.10909125 which is the same version of NDK used in the document. All of them would got compile error (may have different error messages like missing wchar.h ).