cmake执行过程之前没有其他 [英] cmake execute process before anything else

问题描述

我在执行其他操作之前执行CMake时遇到问题。

I've a problem with CMake executing a process before doing anything else.

以下代码段显示了这种情况：

The following code snippet shows the situation:

if(NOT EXISTS "${CMAKE_CURRENT_BINARY_DIR}/generated")
  file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/generated")
  execute_process(
    # This tool generates library sources, which are not known before
    COMMAND "source_file_generator_command"
    # This tool iterates over the generated source tree and creates
    # a proper CMakeLists.txt in the 'generated' directory from the
    # source files found there
    COMMAND "cmake_lists_generator_command"
    WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/generated"
  )
endif()

# At this point the generated subdirectory (with the also
# generated CMakeLists.txt file) shall be included
add_subdirectory(
  "${CMAKE_CURRENT_BINARY_DIR}/generated"
  "${CMAKE_CURRENT_BINARY_DIR}/generated_build"
)
# But the 'add_subdirectory' statement fails due to non-existing
# CMakeLists.txt in the 'generated' source directory at this point

问题是，如上所述，应该添加的子目录中的CMakeLists.txt文件是由特殊程序动态生成的脚本（第一次生成时不知道生成的源）。从字面上看，我需要CMake等待，直到执行if / else块中的所有语句，然后再处理add_subdirectory语句，直到一切都完成为止（生成CMakeLists.txt）。

The problem is, as commented above, that the CMakeLists.txt file in the subdirectory which should be added is generated on the fly by a special script (the generated sources are not known before) during the first CMake run. Literally, I need CMake to wait until all the statements within the if/else block are executed and process the add_subdirectory statement not until everything is done (the CMakeLists.txt is generated). Is there an adequate solution for such a use case?

感谢您的帮助，

Felix

推荐答案

当多个 COMMAND s用于 execute_process ，它们在管道中执行。从此CMake命令的说明：

When several COMMANDs for execute_process are used, they are executed in pipe. From the description of this CMake command:

运行给定序列的一个或多个命令，每个过程的标准输出 piped 到下一个的标准输入。 / p>

Runs the given sequence of one or more commands with the standard output of each process piped to the standard input of the next.

如果要真正顺序执行命令，则需要使用调用<每个命令code> execute_process ：

If you want true sequential execution of the commands, you need to use one call to execute_process per COMMAND:

execute_process(
    COMMAND "source_file_generator_command"
    WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/generated"
)
execute_process(
    COMMAND "cmake_lists_generator_command"
    WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/generated"
)

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