Question

我想从多个子目录中的对象创建一个单独的库，每个子目录包含自己的CMakeLists.txt和OBJECT库技巧，以使多个目标具有不同的编译选项。

以下是文件：

project_dir
|--- subdir1
|    |--- src1.c
|    |--- CMakeLists.txt
|--- subdir2
|    |--- src2.c
|    |--- CMakeLists.txt
|--- CMakeLists.txt

所有CMakeLists.txt的内容

// project_dir/CMakeLists.txt
// what to put here? to make one single library (mainLib)


// project_dir/subdir1/CMakeLists.txt
add_library(lib11 OBJECT src1.c)
set_target_properties(lib11 PROPERTIES COMPILE_FLAGS "some-flags11")

add_library(lib12 OBJECT src1.c)
set_target_properties(lib12 PROPERTIES COMPILE_FLAGS "some-flags12")
// here I would like to add lib11:objects and lib12:objects to mainLib
// how should it be done?

// project_dir/subdir2/CMakeLists.txt
// *** similar to subdir1 but with src2.c that creates lib21 and lib22
// here I would like to add lib21:objects and lib22:objects to mainLib
// how should it be done?

可以独立完成平台吗？感谢。

编辑：基于CMake: how create a single shared library from all static libraries of subprojects?，我可以将cmake文件更改为以下内容，但仍然无法解决我的问题。

// project_dir/subdir1/CMakeLists.txt
add_library(lib11 OBJECT src1.c)
set_target_properties(lib11 PROPERTIES COMPILE_FLAGS "some-flags11")

add_library(lib12 OBJECT src1.c)
set_target_properties(lib12 PROPERTIES COMPILE_FLAGS "some-flags12")

add_library(lib1 STATIC $<TARGET_OBJECTS:lib11> $<TARGET_OBJECTS:lib12>)

// Above add_library cannot be OBJECT which would fix my problem.
// how to append the lib1 (lib11 and lib12) to mainLib?

编辑：根据答案中的建议尝试链接接口库来更新我的帖子。

add_library(lib11 OBJECT test1/sub1/src1.c)
set_target_properties(lib11 PROPERTIES COMPILE_FLAGS "-DF1")

add_library(lib12 OBJECT test1/sub1/src1.c)
set_target_properties(lib12 PROPERTIES COMPILE_FLAGS "-DF2")

add_library(lib1 INTERFACE)
target_sources(lib1 INTERFACE $<TARGET_OBJECTS:lib11>)
target_sources(lib1 INTERFACE $<TARGET_OBJECTS:lib12>)

add_library(lib21 OBJECT test1/sub2/src2.c)
set_target_properties(lib21 PROPERTIES COMPILE_FLAGS "-DF1")

add_library(lib22 OBJECT test1/sub2/src2.c)
set_target_properties(lib22 PROPERTIES COMPILE_FLAGS "-DF2")

add_library(lib2 INTERFACE)
target_sources(lib2 INTERFACE $<TARGET_OBJECTS:lib21>)
target_sources(lib2 INTERFACE $<TARGET_OBJECTS:lib22>)

add_library(PARENT INTERFACE)

target_link_libraries(PARENT INTERFACE lib1)
target_link_libraries(PARENT INTERFACE lib2)

add_library(CORE OBJECT src.c)
add_library(GPARENT STATIC $<TARGET_OBJECTS:CORE>)

target_link_libraries(GPARENT INTERFACE PARENT)

Answer 1

可以将多个 OBJECT 库合并到一个 INTERFACE 库中：

# Create lib1 OBJECT library with some sources, compile flags and so.
add_library(lib1 OBJECT ...)

# Create lib2 OBJECT library with some sources, compile flags and so.
add_library(lib2 OBJECT ...)

# Create INTERFACE library..
add_library(libs INTERFACE)
# .. which combines OBJECT libraries
target_sources(libs INTERFACE $<TARGET_OBJECTS:lib1> $<TARGET_OBJECTS:lib2>)

结果库可以与标准target_include_directories一起使用：

add_library(mainLib <some-source>)
target_link_libraries(mainLib libs)

可以进一步组合 INTERFACE 库：

# Create libs_another INTERFACE library like 'libs' one
add_library(libs_another INTERFACE)
..

# Combine 'libs' and 'libs_another' together
add_library(upper_level_libs INTERFACE)
target_link_libraries(upper_level_libs INTERFACE libs libs_another)

结果库的“链”可以是任何长度。

虽然这种组合OBJECT库的方式看起来很糟糕，但CMake documentation实际上允许它：

虽然在调用target_link_libraries()命令时可能无法直接命名对象库，但可以使用 INTERFACE_SOURCES 接口库间接地“链接”它们。 target属性设置为name $<TARGET_OBJECTS:objlib>。

Answer 2

我只是使用set和PARENT_SCOPE从所有位置收集对象。

根CMakeLists.txt：

set(OBJECTS)

add_subdirectory(lib1)
add_subdirectory(lib2)

add_library(lib STATIC ${OBJECTS})

CMakeLists.txt在子目录中：

add_subdirectory(lib11)

add_library(${PROJECT_NAME} OBJECT src1.c)
list(APPEND OBJECTS $<TARGET_OBJECTS:${PROJECT_NAME}>)
set(OBJECTS ${OBJECTS} PARENT_SCOPE)

CMake将来自不同CMakeLists.txt的对象附加到一个库中

2 个答案: