CMake在构建主目录之前从子目录构建并安装共享库 [英] CMake build and install shared library from subdirectory before building main directory

问题描述

这是我的源代码结构：

cd my_git_repo/
    CMakeLists.txt
    src/
        main.cpp
        mylibrary/
            a.hpp
            b.hpp
            a.cpp
            b.cpp
            CMakeLists.txt

根 CMakeLists.txt ：

cmake_minimum_required(VERSION 3.9)
project(myexe CXX)
add_subdirectory(src/mylibrary)

find_library(mylib NAMES mylibrary.so PATHS "./src/mylibrary/mylibrary.so")
add_executable(myexe src/main.cpp)
target_link_libraries(myexe ${mylib})

mylibrary / CMakeLists.txt 非常简单。它构建一个共享库并安装它们。
理想情况下，应在构建 myexe 之前构建并安装目标，并安装目标。但这不会发生。在构建 mylibrary 之后是 myexe 。安装将在稍后进行。因此， find_library 失败。 pkg_check_modules（）适用于其他共享库，但由于相同的原因而在此处失败。

mylibrary/CMakeLists.txt is very simple. It builds a shared library and installs them. Ideally, mylibrary target should be built and installed before myexe is built. But this doesn't happen. mylibrary is built followed by myexe. Installation happens later. Because of this, find_library fails. pkg_check_modules() works for other shared libraries but fails here because of the same reason.

感谢您的帮助。

编辑：
这个问题与重复的问题有所不同，因为发布到该问题的答案似乎是在静态链接库 target_link_libraries（game引擎）。我想动态链接 .so 库。

This question differs from the duplicate because the answers posted to that question seem to be statically linking the library target_link_libraries(game engine). I want to dynamically link the .so library.

推荐答案

在CMake中，是先构建模块，然后将它们链接在一起。

The idea in CMake is to build modules and then link them together.

您尚未共享 CMakeLists.txt 用于我的库，因此我们无法确定它在做什么。但是，假设它是这样的：

You haven't shared the CMakeLists.txt for my library, so we cannot tell what it is doing. However, assuming that it is something like:

ADD_LIBRARY(mylibrary
  file1.cpp
  file2.cpp
)

由于您指定要 mylibrary 始终链接为共享链接，您还需要通过将 BUILD_SHARED_LIBS 设置为 ON 或通过在SHARED > add_library ：

Since you specified that you want mylibrary to always be linked as shared, you need to tell CMake that as well by either setting BUILD_SHARED_LIBS TO ON or by specifying SHARED in add_library:

ADD_LIBRARY(mylibrary SHARED
  file1.cpp
  file2.cpp
)

这是您的图书馆模块。我们现在将使其保持简单，而不必担心在此处打包库归档文件和安装。

This is your library module. We will keep it simple for now and not worry about packing the library archive and installation here.

现在，回到您的主 CMakeLists.txt 以及如何使 myexe 使用它。由于您已经有 add_subdirectory（src / mylibrary），因此CMake知道 mylibrary 。因此，只需使用模块名称链接即可。既然已经定义了模块，就无需 find_library 。

Now, back to your main CMakeLists.txt and how to make myexe consume it. Since you have already add_subdirectory(src/mylibrary), CMake knows about mylibrary. So simply link it using the module name. There is no need to find_library as you have already defined the module.

add_executable(myexe src/main.cpp)
target_link_libraries(myexe mylibrary)

但是请注意，这是一个非常基本的示例，向您解释CMake是如何工作的。如果您没有构建该库，并且已经安装了该库，则可以调用 find_library 。现代CMake稍微复杂一些，并使用生成器表达式，因此在进行更复杂的项目时，请务必仔细阅读。

Do note, however, this is a very basic example to explain to you how CMake is designed to work. If you aren't building the library, and it is already installed, you would call find_library. Modern CMake is a bit more sophisticated and uses generator expressions, so be sure to read up on that as you progress to more complex projects.

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