# Linker error when building arm84-v8

**URL:** <https://forum.opencv.org/t/linker-error-when-building-arm84-v8/2252>\
**Category:** Android/Java\
**Created:** [March 19, 2021, 9:02am UTC](https://forum.opencv.org/t/linker-error-when-building-arm84-v8/2252 "2021-03-19T09:02:40Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![phillies](https://avatars.discourse-cdn.com/v4/letter/p/d9b06d/32.png) [@phillies](https://forum.opencv.org/u/phillies)\
**Post date:** [March 19, 2021, 9:02am UTC](https://forum.opencv.org/t/linker-error-when-building-arm84-v8/2252/1 "2021-03-19T09:02:40Z")

</div>

I have the same unsolved issue as Fabio in the old forum:  
[https://answers.opencv.org/question/229811/opencv4android-build-error-with-arm64-v8a/](https://answers.opencv.org/question/229811/opencv4android-build-error-with-arm64-v8a/)

I built opencv 4.5.1 which works fine for armeabi-v7a but throws a linker error for arm64-v8

```
[1241/1467] Linking CXX executable bin/opencv_waldboost_detector
FAILED: bin/opencv_waldboost_detector 
: && /opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ --target=aarch64-none-linux-android21 --gcc-toolchain=/opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64 --sysroot=/opt/android-ndk-r21e/toolchains/llvm/prebuilt/linux-x86_64/sysroot -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Winconsistent-missing-override -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Qunused-arguments -fvisibility=hidden -fvisibility-inlines-hidden -O2 -DNDEBUG -DNDEBUG -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libgcc_real.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments -Wl,--gc-sections -Wl,--as-needed modules/xobjdetect/tools/waldboost_detector/CMakeFiles/opencv_waldboost_detector.dir/waldboost_detector.cpp.o -o bin/opencv_waldboost_detector lib/arm64-v8a/libopencv_core.a lib/arm64-v8a/libopencv_imgproc.a lib/arm64-v8a/libopencv_imgcodecs.a lib/arm64-v8a/libopencv_videoio.a lib/arm64-v8a/libopencv_highgui.a lib/arm64-v8a/libopencv_xobjdetect.a lib/arm64-v8a/libopencv_videoio.a -landroid -llog -lmediandk lib/arm64-v8a/libopencv_imgcodecs.a 3rdparty/lib/arm64-v8a/liblibjpeg-turbo.a 3rdparty/lib/arm64-v8a/liblibwebp.a 3rdparty/lib/arm64-v8a/liblibpng.a 3rdparty/lib/arm64-v8a/liblibtiff.a 3rdparty/lib/arm64-v8a/liblibopenjp2.a 3rdparty/lib/arm64-v8a/libIlmImf.a lib/arm64-v8a/libopencv_objdetect.a lib/arm64-v8a/libopencv_calib3d.a lib/arm64-v8a/libopencv_features2d.a lib/arm64-v8a/libopencv_imgproc.a lib/arm64-v8a/libopencv_flann.a lib/arm64-v8a/libopencv_core.a 3rdparty/lib/arm64-v8a/libzlib.a 3rdparty/lib/arm64-v8a/libcpufeatures.a 3rdparty/lib/arm64-v8a/libittnotify.a -ldl -lm -llog 3rdparty/lib/arm64-v8a/libtegra_hal.a 3rdparty/lib/arm64-v8a/libquirc.a -latomic -lm && :
lib/arm64-v8a/libopencv_core.a: error adding symbols: Archive has no index; run ranlib to add one
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

```

system:  
ubuntu 20.10  
openJDK 13  
opencv 4.5.1 w/ contrib  
ndk 21e  
android sdk 30

Any ideas?

---

<div class="post-metadata">

**Author:** ![phillies](https://avatars.discourse-cdn.com/v4/letter/p/d9b06d/32.png) [@phillies](https://forum.opencv.org/u/phillies)\
**Post date:** [March 23, 2021, 11:29am UTC](https://forum.opencv.org/t/linker-error-when-building-arm84-v8/2252/2 "2021-03-23T11:29:05Z")

</div>

cmake seems to cache too much and thus building two different ABIs without deleting CMakeCache.txt between the runs will cause this problem.

This is my working build command:

```auto
rm CMakeCache.txt
cmake \
    -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
    -DANDROID_ABI=arm64-v8a \
    -DANDROID_NATIVE_API_LEVEL=26 \
    -GNinja \
    -DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \
    -DCMAKE_BUILD_TYPE:STRING=Release \
    -DBUILD_TESTS=FALSE -DBUILD_PERF_TESTS=FALSE \
    -DBUILD_ANDROID_EXAMPLES=FALSE \
    -DCMAKE_CONFIGURATION_TYPES:STRING=Release \
    -DBUILD_opencv_highgui:BOOL=OFF \
    -DBUILD_opencv_js_bindings_generator:BOOL=OFF \
    -DBUILD_opencv_objc_bindings_generator:BOOL=OFF \
    -DINSTALL_CREATE_DISTRIB=ON \
    -DBUILD_DOCS:BOOL=OFF -DBUILD_EXAMPLES:BOOL=ON -DWITH_IPP=OFF -DWITH_MSMF=OFF \
../opencv

ninja

```