链接共享 C 库时出现 Android NDK 错误 [英] Android NDK error when linking shared C library

问题描述

I'm trying to link some C files to an NDK project that I'm working on, and set my CMakeLists.txt file up like below.

cmake_minimum_required(VERSION 3.4.1)
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c99 -Wall")


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


add_library( # Specifies the name of the library.
        main SHARED
        main.c
        communication_api.c
        cybtldr_api.c
        cybtldr_parse.c
        cybtldr_command.c
        )
target_link_libraries(main
        communication_api
        cybtldr_api
        cybtldr_parse
        cybtldr_command
        ${log-lib})

I'm getting the error on the step where it's Linking those libraries

[6/6] Linking C shared library /Users/rafa/Code/Labconco-FreezeDry-Android-Refactor/app/build/intermediates/cmake/debug/obj/x86/libmain.so

And error is pretty long

FAILED: : && /Users/rafa/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang  --target=i686-none-linux-android19 --gcc-toolchain=/Users/rafa/Library/Android/sdk/ndk-bundle/toolchains/x86-4.9/prebuilt/darwin-x86_64 --sysroot=/Users/rafa/Library/Android/sdk/ndk-bundle/sysroot -fPIC -isystem /Users/rafa/Library/Android/sdk/ndk-bundle/sysroot/usr/include/i686-linux-android -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -mstackrealign -Wa,--noexecstack -Wformat -Werror=format-security  -std=c99 -Wall -O0 -fno-limit-debug-info  -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a -nostdlib++ --sysroot /Users/rafa/Library/Android/sdk/ndk-bundle/platforms/android-19/arch-x86 -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -L/Users/rafa/Library/Android/sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/x86 -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libmain.so -o /Users/rafa/Code/Labconco-FreezeDry-Android-Refactor/app/build/intermediates/cmake/debug/obj/x86/libmain.so CMakeFiles/main.dir/main.c.o CMakeFiles/main.dir/communication_api.c.o CMakeFiles/main.dir/cybtldr_api.c.o CMakeFiles/main.dir/cybtldr_parse.c.o CMakeFiles/main.dir/cybtldr_command.c.o  -lcommunication_api -lcybtldr_api -lcybtldr_parse -lcybtldr_command -llog -latomic -lm && :

/Users/rafa/Library/Android/sdk/ndk-bundle/toolchains/x86-4.9/prebuilt/darwin-x86_64/lib/gcc/i686-linux-android/4.9.x/../../../../i686-linux-android/bin/ld: error: cannot find - 
lcommunication_api
/Users/rafa/Library/Android/sdk/ndk-bundle/toolchains/x86-4.9/prebuilt/darwin-x86_64/lib/gcc/i686-linux-android/4.9.x/../../../../i686-linux-android/bin/ld: error: cannot find -lcybtldr_api
/Users/rafa/Library/Android/sdk/ndk-bundle/toolchains/x86-4.9/prebuilt/darwin-x86_64/lib/gcc/i686-linux-android/4.9.x/../../../../i686-linux-android/bin/ld: error: cannot find -lcybtldr_parse
/Users/rafa/Library/Android/sdk/ndk-bundle/toolchains/x86-4.9/prebuilt/darwin-x86_64/lib/gcc/i686-linux-android/4.9.x/../../../../i686-linux-android/bin/ld: error: cannot find -lcybtldr_command

The gist is this

error: cannot find -lcybtldr_command
error: cannot find -lcybtldr_api
error: cannot find -lcybtldr_parse
error: cannot find -lcybtldr_command

It looks like it's happening when it's trying to link all of the files in the add_library() besides the main which is in the same directory as the other files it can't link

What am I missing?

解决方案

I think you misunderstand the cmake syntax. Below is enough for your case.

target_link_libraries(
    main
    ${log-lib})

Below are source files, NOT library names.

communication_api
cybtldr_api
cybtldr_parse
cybtldr_command

So, you cmake statements are not correct.

If you want to make less confusing, try to make below changes.

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


add_library( # Specifies the name of the library.
        my-native-lib SHARED
        main.c
        communication_api.c
        cybtldr_api.c
        cybtldr_parse.c
        cybtldr_command.c
        )
target_link_libraries(my-native-lib
        ${log-lib})

But, remember to change your Java side as well, see below example:

// Used to load the 'my-native-lib' library on application startup.
static {
    System.loadLibrary("my-native-lib");
}

I just enclose my JniExample project in case you need: https://github.com/russell-shizhen/JniExample

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