c++ - Cmake 外部库.a

Question

我这里有一个外部库:

${PROJECT_SOURCE_DIR}/thirdparty/yaml-cpp/

它是由 Makefile 制作的:thirdparty/Makefile。我正在像这样执行该 makefile:

add_custom_target(
   yaml-cpp
   COMMAND make
   WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/thirdparty
)

然后我尝试链接构​​建到 thirdparty/yaml-cpp/build/libyaml-cpp.a 的库。 这是不起作用的部分:

target_link_libraries(load_balancer_node ${CMAKE_SOURCE_DIR}/thirdparty/yaml-cpp/build/libyaml-cpp.a)

我得到错误:

  Target "yaml-cpp" of type UTILITY may not be linked into another target.
  One may link only to STATIC or SHARED libraries, or to executables with the
  ENABLE_EXPORTS property set.

我如何执行该 makefile 并链接 .a 文件？

Answer 1

因此，cmake 无法确定此处的依赖关系是有道理的:它必须解析 makefile 并找到输出。你必须告诉它输出某人。据我所知，最好的方法是使用 custom_command 而不是自定义目标:

add_custom_command(
    OUTPUT ${CMAKE_SOURCE_DIR}/thirdparty/yaml-cpp/build/libyaml-cpp.a
    COMMAND make
    WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/thirdparty)
 add_custom_target(
   yaml-cpp
   DEPENDS ${CMAKE_SOURCE_DIR}/thirdparty/yaml-cpp/build/libyaml-cpp.a)
 ...
 add_dependencies(load_balancer_node yaml-cpp)
 target_link_libraries(load_balancer_node ${CMAKE_SOURCE_DIR}/thirdparty/yaml-cpp/build/libyaml-cpp.a)

虽然我遇到了链接器问题(愚蠢的 Windows 机器)，但是 cmake 在尝试链接之前工作并创建了库。