如何在安装时完全忽略BUILD_INTERFACE关联的依赖库？

我通过$<BUILD_INTERFACE:>表达式链接私有库，这些库不会出现在导出目标中，但它们自身链接的库会被包含进来，执行install规则时这些依赖库也会被自动安装。我无权修改这些依赖库的代码，请问怎么阻止它们被安装？

测试示例 #

TestingExports/CMakeLists.txt #

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(TestinExports CXX)

add_subdirectory(ThatThing)

file(WRITE main.cc "int main() { }")
add_executable(${PROJECT_NAME} main.cc)
target_link_libraries(${PROJECT_NAME} PRIVATE $<BUILD_INTERFACE:ThatThing>)

install(TARGETS ${PROJECT_NAME} EXPORT ${PROJECT_NAME}Config)
install(EXPORT ${PROJECT_NAME}Config DESTINATION lib/cmake)

ThatThing/CMakeLists.txt #

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(ThatThing CXX)

add_subdirectory(ThoseLibraries)

file(WRITE that_thing.cc "void Function() { }")
add_library(${PROJECT_NAME} STATIC that_thing.cc)
target_link_libraries(${PROJECT_NAME} PRIVATE ThoseLibraries)

ThatThing/ThoseLibraries/CMakeLists.txt #

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(ThoseLibraries CXX)

file(WRITE those_libraries.cc "void AnotherFunction() { }")
add_library(${PROJECT_NAME} STATIC those_libraries.cc)

install(TARGETS ${PROJECT_NAME} EXPORT ${PROJECT_NAME}Config)
install(EXPORT ${PROJECT_NAME}Config DESTINATION lib/cmake)

构建安装后的现象 #

执行以下命令后，ThoseLibraries会被自动安装：

$ cmake -B build -DCMAKE_INSTALL_PREFIX=$PWD/install
$ cmake --build build
$ cmake --install build
-- Install configuration: ""
-- Installing: /tmp/export_set/install/lib/libThoseLibraries.a
-- Installing: /tmp/export_set/install/lib/cmake/ThoseLibrariesConfig.cmake
-- Installing: /tmp/export_set/install/lib/cmake/ThoseLibrariesConfig-noconfig.cmake
-- Installing: /tmp/export_set/install/bin/TestinExports
-- Installing: /tmp/export_set/install/lib/cmake/TestinExportsConfig.cmake
-- Installing: /tmp/export_set/install/lib/cmake/TestinExportsConfig-noconfig.cmake

已尝试的无效方案 #

• 使用EXCLUDE_FROM_ALL完全无效：不想将目标从ALL目标中移除，同时需要保留IDE所需的完整项目信息。
• 重写install()宏的方案失效：该方法会导致CMake忽略所有安装规则，无法保留自身项目的私有安装逻辑，示例代码如下：

macro(install)
endmacro()

add_subdirectory(ThatThing)

macro(install)
  _install(${ARGV})
endmacro(install)

可行解决方案 #

通过临时禁用CMake的安装规则，跳过依赖库的install指令，同时保留自身项目的安装逻辑。具体修改主项目的CMakeLists.txt如下：

cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
project(TestinExports CXX)

# 保存当前安装规则状态，临时禁用所有install规则
set(ORIGINAL_SKIP_INSTALL_RULES ${CMAKE_SKIP_INSTALL_RULES})
set(CMAKE_SKIP_INSTALL_RULES ON)

# 添加依赖子目录，此时子目录中的install规则会被忽略
add_subdirectory(ThatThing)

# 恢复原始安装规则状态，确保主项目的install规则正常执行
set(CMAKE_SKIP_INSTALL_RULES ${ORIGINAL_SKIP_INSTALL_RULES})

file(WRITE main.cc "int main() { }")
add_executable(${PROJECT_NAME} main.cc)
target_link_libraries(${PROJECT_NAME} PRIVATE $<BUILD_INTERFACE:ThatThing>)

install(TARGETS ${PROJECT_NAME} EXPORT ${PROJECT_NAME}Config)
install(EXPORT ${PROJECT_NAME}Config DESTINATION lib/cmake)

原理说明 #

• CMAKE_SKIP_INSTALL_RULES是CMake内置变量，当设为ON时，所有后续的install指令都会被跳过。
• 在添加依赖子目录前临时开启该变量，就能忽略依赖库中的所有安装逻辑；添加完成后恢复变量状态，主项目的安装规则不受影响。
• 该方案无需修改依赖库的代码，也不会移除ALL目标中的依赖库构建任务，能保留IDE的完整项目信息。

内容的提问来源于stack exchange，提问作者Ghasem Ramezani