尝试为 Android 构建 PyQt5 应用程序并收到链接错误：找不到 -lc++

Question

I try to build the demo app from pyqtdeploy and I am running into this linker error.
cannot find -lc++

Here is the command which generates the error:

/home/art/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ -D__ANDROID_API__=27 -target aarch64-none-linux-android -gcc-toolchain /home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64 -fno-limit-debug-info -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a --sysroot=/home/art/Android/Sdk/ndk-bundle/platforms/android-27/arch-arm64/ -Wl,-soname,libpyqt-demo.so -Wl,-rpath=/home/art/Qt/5.12.3/android_arm64_v8a/lib -Wl,--no-undefined -Wl,-z,noexecstack -shared -o libpyqt-demo.so pyqtdeploy_main.o pyqtdeploy_start.o pdytools_module.o _abc.o _bisectmodule.o blake2b_impl.o blake2module.o blake2s_impl.o _datetimemodule.o _hashopenssl.o _heapqmodule.o _math.o _posixsubprocess.o _randommodule.o sha3module.o _ssl.o _struct.o binascii.o mathmodule.o selectmodule.o socketmodule.o zlibmodule.o qrc_pyqtdeploy.o   -L/home/art/Sourcecode/pyqtdeploy-2.4/demo/sysroot-android-64/lib -L/home/art/Sourcecode/pyqtdeploy-2.4/demo/sysroot-android-64/lib/python3.7/site-packages/PyQt5 -lQtAndroidExtras -lQtCore -lQtGui -lQtNetwork -lQtWidgets -lcrypto -lpython3.7 -lsip -lssl -lz -L/home/art/Qt/5.12.3/android_arm64_v8a/lib -lQt5Widgets -L/opt/android/android-ndk-r18b/sources/cxx-stl/llvm-libc++/libs/arm64-v8a -lQt5Gui -lQt5Network -lQt5AndroidExtras -lQt5Core -lGLESv2  -L/home/art/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a /home/art/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++.so.27 -llog -lz -lm -ldl -lc -v
Android (5220042 based on r346389c) clang version 8.0.7 (https://android.googlesource.com/toolchain/clang b55f2d4ebfd35bf643d27dbca1bb228957008617) (https://android.googlesource.com/toolchain/llvm 3c393fe7a7e13b0fba4ac75a01aa683d7a5b11cd) (based on LLVM 8.0.7svn)
Target: aarch64-none-linux-android
Thread model: posix
InstalledDir: /home/art/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin
Found candidate GCC installation: /home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x
Selected GCC installation: /home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x
Candidate multilib: .;@m64
Selected multilib: .;@m64
 "/home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x/../../../../aarch64-linux-android/bin/ld" --sysroot=/home/art/Android/Sdk/ndk-bundle/platforms/android-27/arch-arm64/ -EL --fix-cortex-a53-843419 -z now -z relro --hash-style=both --enable-new-dtags --eh-frame-hdr -m aarch64linux -shared -o libpyqt-demo.so /home/art/Android/Sdk/ndk-bundle/platforms/android-27/arch-arm64//usr/lib/crtbegin_so.o -L/home/art/Sourcecode/pyqtdeploy-2.4/demo/sysroot-android-64/lib -L/home/art/Sourcecode/pyqtdeploy-2.4/demo/sysroot-android-64/lib/python3.7/site-packages/PyQt5 -L/home/art/Qt/5.12.3/android_arm64_v8a/lib -L/opt/android/android-ndk-r18b/sources/cxx-stl/llvm-libc++/libs/arm64-v8a -L/home/art/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a -L/home/art/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/lib64/clang/8.0.7/lib/linux/aarch64 -L/home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x -L/home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x/../../../../aarch64-linux-android/lib/../lib64 -L/home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x/../../../../aarch64-linux-android/lib -L/home/art/Android/Sdk/ndk-bundle/platforms/android-27/arch-arm64//usr/lib --exclude-libs libgcc.a --exclude-libs libatomic.a -soname libpyqt-demo.so -rpath=/home/art/Qt/5.12.3/android_arm64_v8a/lib --no-undefined -z noexecstack pyqtdeploy_main.o pyqtdeploy_start.o pdytools_module.o _abc.o _bisectmodule.o blake2b_impl.o blake2module.o blake2s_impl.o _datetimemodule.o _hashopenssl.o _heapqmodule.o _math.o _posixsubprocess.o _randommodule.o sha3module.o _ssl.o _struct.o binascii.o mathmodule.o selectmodule.o socketmodule.o zlibmodule.o qrc_pyqtdeploy.o -lQtAndroidExtras -lQtCore -lQtGui -lQtNetwork -lQtWidgets -lcrypto -lpython3.7 -lsip -lssl -lz -lQt5Widgets -lQt5Gui -lQt5Network -lQt5AndroidExtras -lQt5Core -lGLESv2 /home/art/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++.so.27 -llog -lz -lm -ldl -lc -lc++ -lm -lgcc -ldl -lc -lgcc -ldl /home/art/Android/Sdk/ndk-bundle/platforms/android-27/arch-arm64//usr/lib/crtend_so.o
/home/art/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x/../../../../aarch64-linux-android/bin/ld: cannot find -lc++
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

Has anybody got an idea how to fix this?

Answer 1

The compiler is missing this file: /home/art/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++.so.27 given as a dependency in the call. look if it is on your system. If not you can try to find it with s.th. like:

find /home/art/ -name "libc++.so.27"

Or even more generic:

find /home/art -name "libc++.so*"

to find other versions of this file. If you can't find it in the expected version, I'd guess you don't have the proper SDK. Try to clean up. (don't know what you're doing, but maybe download a version of the demo app which fits to the SDK?!)

Answer 2

Just in case other people are also running into a similar problem.
I could solve this problem using NDK 19 instead of NDK-20.