cmake：对对象库的依赖 [英] cmake: dependencies on object libraries

问题描述

假定以下目录结构：

CMakeLists.txt
libA
    contents: a.cpp 
              a.h
src
    contents: hello.cpp
              target1.cpp
              target2.cpp
include
    - contents: hello.h

我有一个静态库 A ，用于项目的主要源代码。

I have a static library A, used within the main source code of the project.

尝试1 ：

. . .
add_executable(t1 src/target1.cpp src/hello.cpp)
add_dependancies(libA)
target_include_directories(t1 PRIVATE ${PROJECT_SOURCE_DIR}/include
target_link_libraries(t1 PRIVATE /path/to/libA)
. . .

此功能适用于 t1 ，但是，如果要编译 target2.cpp ，则需要重复此过程，因此 hello.o 生成两次。

This works for t1, however, if I want to compile target2.cpp I would need to repeat this process, hence hello.o is generated twice.

尝试2 ：
我正在考虑更改此方法以生成一个 hello.cpp 的对象库，只是将对象库添加到目标中，但是，由于找不到库 A <中定义的标头，我遇到了编译问题/ em>，因为首先编译了对象库，并且尚未将头文件复制到 CMakeFiles 。

Attempt 2: I was thinking to change this approach to generate an object library for hello.cpp, and simply add the object library to the targets. Yet, I get compilation problems as it cannot find the headers defined in library A as the object library is compiled first and the heade files are not yet copied to the CMakeFiles.

. . .
add_library(libA src/hello.cpp)
add_executable(t1 src/target1.cpp $<TARGET_OBJECTS:libA>)
add_dependancies(libA)
target_include_directories(t1 PRIVATE ${PROJECT_SOURCE_DIR}/include
target_link_libraries(t1 PRIVATE /path/to/libA)
. . .

是否可以定义依赖项，因此静态库 A

Is there a way to define a dependancy, so that the static library A is compiled before?

推荐答案

在注释中，您提到了 libA ExternalProject_Add 将$ c>带入构建系统。这意味着您在同一个 CMakeLists.txt 中混合了常规项目和外部项目，因此强烈建议不要这样做。

In the comments, you've mentioned that libA is actually brought into the buildsystem using ExternalProject_Add. Which means that you're mixing "normal" and external projects in the same CMakeLists.txt, and that's highly discouraged.

使用ExternalProject的首选方法是所谓的Superbuild方法：将 all 项目视为外部项目，并使用 ExternalProject_Add 将其添加，包括您自己的项目。这样，主CMakeList就变成了超级构建—。子项目的容器和驱动程序。在此级别上，您可以根据需要在各个项目之间引入依赖关系。

The preferred way of working with ExternalProject is the so-called Superbuild approach: treat all the projects as external and add them with ExternalProject_Add, including your own project. That way, the master CMakeList becomes just the superbuild — a container and driver for subprojects. At this level, you can introduce dependencies between the individual projects as necessary.

配置并构建一次超级构建，以正确设置所有项目。然后，将其降低一级，就好像您的项目是独立的一样；所有依赖项都已经准备好了。

Configure and build the superbuild once to get all projects set up correctly. After that, go one level lower and work on your project as if it was standalone; all dependencies will have been already prepared and ready.

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