Overriding a default option(…) value in CMake from a parent CMakeLists.txt

子 CMakeLists.txt

option(BUILD_FOR_ANDROID "Build For Android" OFF)

if(SYSTEM.Android AND NOT BUILD_FOR_ANDROID)
    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${NATIVE_LIBRARY_OUTPUT}/${ANDROID_ABI})
endif()

父 CMakeLists.txt

set(BUILD_FOR_ANDROID ON)
add_subdirectory(${CHILD_ROOT_DIR}/ ${CMAKE_CURRENT_SOURCE_DIR}/build)

执行如下命令的时候：

/Users/xxxx/Library/Android/sdk/cmake/3.6.4111459/bin/cmake --trace-expand \
-H/Users/xxxx/Source/example/demo/android/app \
-B/Users/xxxx/Source/example/demo/android/app/.externalNativeBuild/cmake/debug/arm64-v8a \
-DANDROID_ABI=arm64-v8a \
-DANDROID_PLATFORM=android-21 \
-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=/Users/xxxx/Source/example/demo/android/app/build/intermediates/cmake/debug/obj/arm64-v8a \
-DCMAKE_BUILD_TYPE=Debug \
-DANDROID_NDK=/Users/xxxx/Library/Android/android-ndk-r16b \
-DCMAKE_TOOLCHAIN_FILE=/Users/xxxx/Library/Android/android-ndk-r16b/build/cmake/android.toolchain.cmake \
-DCMAKE_MAKE_PROGRAM=/Users/xxxx/Library/Android/sdk/cmake/3.6.4111459/bin/ninja \
-G"Android Gradle - Ninja" \
-DANDROID_ARM_NEON=TRUE \
-DANDROID_TOOLCHAIN=gcc \
-DANDROID_PLATFORM=android-21 \
-DANDROID_STL=gnustl_shared

会观察到生成的配置文件中 BUILD_FOR_ANDROID 不一定能生效。

需要如下配置才行：
父 CMakeLists.txt

set(BUILD_FOR_ANDROID ON CACHE BOOL "" FORCE)
add_subdirectory(${CHILD_ROOT_DIR}/ ${CMAKE_CURRENT_SOURCE_DIR}/build)

参考链接

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• Overriding a default option(…) value in CMake from a parent CMakeLists.txt'
• Override option in CMake subproject