CMake 错误:“add_subdirectory 未给出二进制目录"

问题描述

我正在尝试将 Google Test 集成到更大项目的子项目中，但找不到令我满意的解决方案.

I am trying to integrate Google Test into the subproject of bigger project and I cannot find the solution that would be satisfying for me.

我有两个限制:

• Google Test 的源代码已经存在于项目结构中(因此不能使用 URL 从 git 存储库下载它)
• Google Test 的源代码不是我的子项目的子目录(并且永远不会)

所以当我尝试做这样的事情时:

So when I tried to do something like this:

add_subdirectory( ${GOOGLETEST_PROJECT_LOCATION})

我收到了:

CMake Error at unit_tests/CMakeLists.txt:10 (add_subdirectory):
  add_subdirectory not given a binary directory but the given source
  directory "${GOOGLETEST_PROJECT_LOCATION}" is not a subdirectory of
  "${UNIT_TEST_DIRECTORY}".  When
  specifying an out-of-tree source a binary directory must be explicitly
  specified.

另一方面，ExternalProject_Add 可能是一个解决方案，但当我根本不想下载源代码并使用项目中特定位置的源代码时，我不知道该如何使用它.

On the other hand maybe ExternalProject_Add could be a solution but I do not know how shall I use it when I do not want to download sources at all and use sources from specific location in the project.

项目结构看起来更像这样:

Project structure looks more or like like this:

3rdparty 
    |--googletest 
...
subproject
   |--module1
      |--file1.cpp
      |--CMakeLists.txt
   |--module2
      |--file2.cpp
      |--CMakeLists.txt
   |--include
      |--module1
          |--file1.h
      |--module2
          |--file2.h
   |--unit_test
       |--module1
           |--file1test.cpp
       |--module2
           |--file2test.cpp
       |--CMakeLists.txt
   |--CMakeLists.txt
CMakeLists.txt

推荐答案

错误信息很明确 - 您还应该为 googletest 指定构建目录.

The error message is clear - you should also specify build directory for googletest.

# This will build googletest under build/ subdirectory in the project's build tree
add_subdirectory( ${GOOGLETEST_PROJECT_LOCATION} build)

当您将 relative 路径(作为 source 目录)提供给 add_subdirectory 调用时，CMake 会自动为 使用相同的相对路径>build 目录.

When you give relative path (as a source directory) to add_subdirectory call, CMake automatically uses the same relative path for the build directory.

但是在绝对源路径的情况下(当这个路径不在你的源代码树中时)，CMake无法猜测build目录，你需要提供它明确:

But in case of absolute source path (and when this path isn't in your source tree), CMake cannot guess build directory, and you need to provide it explicitly:

另见文档，了解add_subdirectory 命令.

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