在 cmake 中设置共享库和静态库之间的链接

Question

在阅读了一些关于静态库和共享库的文章后，我想我知道其中的区别，但我仍然无法找到解决我的用例的方法。我有以下项目结构

Project
├── A
│   ├── A.cpp
│   ├── A.h
│   └── CMakeLists.txt
├── B
│   ├── CMakeLists.txt
│   └── B.cpp
├── CMakeLists.txt

在文件夹A 我有：

//content of A.h
#include <opencv2/opencv.hpp>
cv::Mat A_load_image(std::string file_path);

//content of A.cpp
#include "A.h"
cv::Mat A_load_image(std::string file_path) {
    return cv::imread(file_path);
}

// content of CMakelists.txt in A
set(TARGET A)
add_library( ${TARGET} STATIC A.cpp )
target_include_directories(${TARGET} PUBLIC
        ${CMAKE_CURRENT_SOURCE_DIR}
        /path/to/opencv/include/folder )
link_directories( /path/to/opencv/lib/folder)
target_link_libraries( ${TARGET} PUBLIC libopencv_core.a )

然后在我的文件夹B 我有：

//content of B.cpp
#include "A.h"

cv::Mat B_load_image() {
    return A_load_image("img.bmp");
}

// content of CMakelists.txt in B
set(TARGET B)

add_library(A STATIC IMPORTED)
set_target_properties(A PROPERTIES IMPORTED_LOCATION /PATH/TO/libA.a)

add_library(${TARGET} SHARED B.cpp)
target_include_directories(${TARGET} PUBLIC
        ${CMAKE_CURRENT_SOURCE_DIR}/../A
        /path/to/opencv/include/folder )
 
target_link_libraries(${TARGET} PUBLIC A libopencv_core.a)

当然我在项目根目录中有 CMakelists.txt 文件：

cmake_minimum_required(VERSION 3.4.1)
add_subdirectory(B)
add_subdirectory(A)

我对这个项目有以下疑问。

1. 如何告诉 cmake 先编译 B，这样当我为 A 导入 B 时，如果有任何变化，它已经更新了
2. 上述设置不起作用，因为我在链接 B 时出错：“找不到 -lopencv_core”，我已经使用 PUBLIC 链接 A，我还尝试将 link_directories( /path/to/opencv/lib/folder) 添加到 B 的 CMakelists.txt 中，但仍然无法正常工作。 我相信“找不到-lopencv_core”失败了，因为它正在寻找动态库，例如libopencv_core.so而不是静态库。但是为什么会这样以及我如何强制链接到静态库？

Answer 1

尝试对象库：

cmake_minimum_required(VERSION 3.11)
add_subdirectory(A)
add_subdirectory(B)

# A/CMakeLists.txt
find_package(OpenCV REQUIRED)
add_library(A OBJECT A.cpp)
target_include_directories(A PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
target_link_libraries(A PUBLIC ${OpenCV_LIBS})

# B/CMakeLists.txt
add_library(B SHARED B.cpp)
target_include_directories(B PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
target_link_libraries(B PUBLIC A)
# also try
target_link_options(B PRIVATE "-Wl,--whole-archive")
# or maybe
target_link_options(B PRIVATE "-Wl,--export-all-symbols")
# or maybe also
target_sources(B $<TARGET_OBJECTS:A>)