Are CMAKE_SOURCE_DIR and PROJECT_SOURCE_DIR the same in CMake?

This page contains a good summary of variables CMake already defines for us. I feel that some variables are the same. Take the example of CMAKE_SOURCE_DIR and PROJECT_SOURCE_DIR for example. They are the same, referring to the folder where the top level CMakeLists.txt is defined. So my question is: are there subtle difference between them? Thanks.

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最佳答案

这些变量之间有一个差异。CMAKE_SOURCE_DIR确实引用了定义顶级 CMakeLists.txt 的文件夹。但是，PROJECT_SOURCE_DIR引用包含最新 project()命令的 CMakeLists.txt 文件夹。

例如，假设您有一个名为 Outer的顶级项目，该项目包含一个子目录，其中有一个名为 Inner的项目。Outer的 CMakeLists.txt 有:

project(Outer)
add_subdirectory(Inner)

以及 Inner:

project(Inner)

然后在这两个 CMakeList 文件中，CMAKE_SOURCE_DIR将引用 Outer的源目录。但是，虽然 Outer的 PROJECT_SOURCE_DIR也是同样的 dir，但是 Inner的情况并非如此。Inner的 PROJECT_SOURCE_DIR是包含其 CMakeLists.txt 的子目录。

这种差异适用于所有 PROJECT_<var>和 CMAKE_<var>变量。