Android NDK.Build command failed. Undefined reference. clang++: error: linker command failed with exit code 1

Issue

I am getting this error when I try to make separate libraries, with add_library(mycpp-lib ...) and add_library(native-lib ...). When I build using single add_library(), I do not get the error.

Note: Both libraries (libmycpp-lib.so and libnative-lib.so) are generated successfully.

This is the error I am getting:

Build command failed.
Error while executing process /Users/vk/Library/Android/sdk/cmake/3.10.2.4988404/bin/ninja with arguments {-C /Users/vk/Development/MyNativeApp1/app/.cxx/cmake/debug/arm64-v8a mycpp-lib native-lib}
ninja: Entering directory `/Users/vk/Development/MyNativeApp1/app/.cxx/cmake/debug/arm64-v8a'
[1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o
[2/2] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/arm64-v8a/libnative-lib.so
FAILED: ../../../../build/intermediates/cmake/debug/obj/arm64-v8a/libnative-lib.so 
: && /Users/vk/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++ --target=aarch64-none-linux-android21 --gcc-toolchain=/Users/vk/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64 --sysroot=/Users/vk/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/sysroot -fPIC -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -fno-addrsig -Wa,--noexecstack -Wformat -Werror=format-security   -O0 -fno-limit-debug-info  -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Qunused-arguments -Wl,-z,noexecstack -shared -Wl,-soname,libnative-lib.so -o ../../../../build/intermediates/cmake/debug/obj/arm64-v8a/libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o  -llog -latomic -lm && :
CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o: In function `Java_vikas_example_com_mynativeapp1_MainActivity_stringFromJNI':
/Users/vk/Development/MyNativeApp1/app/.cxx/cmake/debug/arm64-v8a/../../../../src/main/cpp/native-lib.cpp:14: undefined reference to `addtwo(int, int)'
/Users/vk/Development/MyNativeApp1/app/.cxx/cmake/debug/arm64-v8a/../../../../src/main/cpp/native-lib.cpp:16: undefined reference to `array_pointer(int*, int)'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

Here is my CMakeLists.txt:

cmake_minimum_required(VERSION 3.4.1)
set(CMAKE_VERBOSE_MAKEFILE on)

aux_source_directory(src/main/cpp/cpp_basic/airthmatic CPP_SRC)
aux_source_directory(src/main/cpp/cpp_basic CPP_BASIC_SRC)

include_directories(src/main/cpp/cpp_basic/airthmatic)
include_directories(src/main/cpp/cpp_basic)

add_library( # Sets the name of the library.
        native-lib

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        src/main/cpp/native-lib.cpp
        )

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)

add_library(mycpp-lib

            SHARED

        ${CPP_SRC}
        ${CPP_BASIC_SRC})


target_link_libraries( # Specifies the target library.
        native-lib


        ${mycpp-lib}

        ${log-lib}

        )

Solution

The mycpp-lib target name is not a variable defined with the set() command, so expanding it with ${mycpp-lib} yields an empty string. When using target_link_libraries(), you can simply put the target name (without ${}) when linking previously-defined targets:

target_link_libraries( # Specifies the target library.
        native-lib
        mycpp-lib
        ${log-lib}
        )

Note, for log-lib you do need the ${} to expand the cached variable defined by the find_library() call.

Answered By - Kevin