多个CMakeLists [英] Multiple CMakeLists

问题描述

假设我的目录结构如下：

Suppose I have a directory structure as follows:

/main.cpp
/CMakeLists.txt
/foo/foo.cpp
/foo/CMakeLists.txt

其中我的 /CMakeLists.txt 文件包含以下内容：

where my /CMakeLists.txt file contains the following:

project(Test)
add_subdirectory("foo")
add_executable(Test main.cpp foo/foo.cpp)
target_link_libraries(Test ${OpenNI_LIB})

和我的 /foo/CMakeLists.txt 文件包含以下内容：

and my /foo/CMakeLists.txt file contains the following:

find_library(OpenNI REQUIRED)

当我在第一个 CMakeLists.txt 中使用行 add_subdirectory（ foo）时，实际上会发生什么？是否在 foo 中搜索第二个 CMakeLists.txt 文件，并将内容添加到第一个文件中？定义第二个文件的任何变量在第一个文件中可用吗？特别是在此示例中，假设变量 $ {OpenNI_LIB} 在第二个变量中定义，则该变量会在第一个变量中被识别吗？

When I use the line add_subdirectory("foo") in the first CMakeLists.txt, what actually happens? Does it search for a second CMakeLists.txt file in foo, and add the contents to the first? Will any variables defined the second file be available in the first? And specifically in this example, will the variable ${OpenNI_LIB} be recognised in the first, given that it is defined in the second?

谢谢。

推荐答案

它是否搜索第二个CMakeLists.txt文件在foo

Does it search for a second CMakeLists.txt file in foo

是的，确实如此

并将内容添加到第一个吗？

and add the contents to the first?

不是。它执行许多配置操作，例如查找库等，并生成单独的Makefile和/或其他构建时工件。

No it doesn't. It performs a number of configuring actions such as finding libraries etc and a generates separate Makefile and/or other build-time artifacts.

在此示例中，假设变量$ {OpenNI_LIB}是在第二个变量中定义的，那么它会在第一个变量中被识别吗？

And specifically in this example, will the variable ${OpenNI_LIB} be recognised in the first, given that it is defined in the second?

否，除非这样的构造

find_library(OpenNI REQUIRED) # this sets variables for OpenNI
                              # in the context of foo/CMakeLists.txt
set(OpenNI_LIB ${OpenNI_LIB} PARENT_SCOPE) # this copies ${OpenNI_LIB}
                              # into the context of /CMakeLists.txt

用于 foo / CMakeLists.txt

在子目录的CMakeLists.txt中定义的默认变量也将在子目录的子目录中定义，也就是说，如果 foo / 依次包含 bar / 和自己的 CMakeL ists.txt ，然后在 bar / 的 CMakeLists.txt $ {OpenNI_LIB}

By default variables defined in a subdirectory's CMakeLists.txt are also defined in the subdirectory's subdirectories, that is if foo/ in turn contained bar/ with its own CMakeLists.txt, then within bar/'s CMakeLists.txt ${OpenNI_LIB} would be set.

PS 消息（状态某些带有$ {VAR}的消息）在 CMakeLists.txt 的可疑位置是您的朋友。只需查看cmake输出即可。

P.S. message(STATUS "Some message with ${VAR}") in doubtful places of CMakeLists.txt is your friend. Just look into cmake output.

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