如何在CMake中将对脚本的依赖项添加到目标？ [英] How do I add a dependency on a script to a target in CMake?

问题描述

程序链接后，我需要对其进行一些后处理。我添加了 add_custom_command（TARGET ... ，效果很好。但是，此额外的自定义命令运行了一个脚本（未生成；已检入代码库），并且如果该脚本发生更改，我希望该目标被认为已过时，以便可以正确地重建它。

add_dependencies 规则似乎仅在顶级元素之间起作用，而这不是（只是一个脚本），并且<$ c $的这种形式没有 DEPENDS 元素c>我可以使用的add_custom_command 。

我该怎么做？

解决方案

不幸的是，这有点令人费解，但是您可以使用 add_custom_target 以通过脚本处理模式调用CMake -P 。

您需要使用 add_custom_target ，因为即使所有内容都是最新的，它也会一直执行。

我们已经做出了此决定，需要具有自定义目标执行命令，这些命令将检查您的后处理脚本文件的新版本（让我们将其称为 my_script，并假设它位于您的根目录中），如果更改了，则会导致从属目标退出日期。

这将包括：

1. 比较 my_script的先前副本表示源树中当前的 my_script。如果当前的 my_script不同，或者不存在副本（即这是CMake的第一次运行），则...


2. 将 my_script从源树复制到构建树，然后...


3. 触摸从属目标的源文件，使其过时。 li>
   

CMake脚本中所需的所有命令可以使用 execute_process 调用 cmake -E 。

因此CMake脚本（称为 copy_script .cmake）类似于：

  execute_process（COMMAND $ {CMAKE_COMMAND} -E compare_files 
 $ {OriginalScript } $ {CopiedScript} RESULT_VARIABLE结果）
 if（结果）
 execute_process（COMMAND $ {CMAKE_COMMAND} -E复制
 $ {OriginalScript} $ {CopiedScript}）
 execute_process（COMMAND $ {CMAKE_COMMAND} -E touch_nocreate $ {FileToTouch}）
 endif（）
  

CMake脚本需要通过 -D args 调用 -P 之前，因此，调用CMakeLists.txt的内容如下：

  set（FileToTouch $ {CMAKE_SOURCE_DIR} /src/main.cpp）
 
 add_custom_target（CopyScript ALL $ {CMAKE_COMMAND} 
 -DOriginalScript = $ {CMAKE_SOURCE_DIR} / my_script 
 -DCopiedScript = $ {CMAKE_BINARY_DIR} / my_script 
 -DFileToTouch = $ { FileToTouch} 
 -P $ {CMAKE_SOURCE_DIR} /copy_script.cmake）
 
 add_executable（MyExe $ {FileToTouch}）
  

这将导致可执行文件的完全重建，因为它认为源文件已被修改。如果只需要强制重新链接，则可能会有更好的方法来实现。 / p>

After my program is linked I need to perform some post-processing on it. I added a add_custom_command(TARGET ... and that worked fine. However, this extra custom command runs a script (that is not generated; it's checked into the codebase), and I want the target to be considered out of date if that script changes so it will be rebuilt properly.

The add_dependencies rule seems to only work between top-level elements, which this is not (it's just a script), and there's no DEPENDS element in this form of the add_custom_command that I can use.

How do I do this?

解决方案

It's unfortunately a bit convoluted, but you can use add_custom_target to invoke CMake in script-processing mode via -P.

You need to use add_custom_target here since it will always execute, even if everything's up to date.

Having made this decision, we need to have the custom target execute commands which will check for a new version of your post-processing script file (let's call this "my_script" and assume it's in your root dir), and if it's changed cause your dependent target to go out of date.

This would comprise:

1. Compare a previous copy of "my_script" to the current "my_script" in the source tree. If the current "my_script" is different, or if the copy doesn't exist (i.e. this is the first run of CMake) then...
2. Copy "my_script" from the source tree to the build tree, and...
3. Touch a source file of the dependent target so that it goes out of date.

All of the commands required inside the CMake script can be achieved using execute_process to invoke cmake -E.

So the CMake script (called e.g. "copy_script.cmake") would be something like:

execute_process(COMMAND ${CMAKE_COMMAND} -E compare_files
                    ${OriginalScript} ${CopiedScript} RESULT_VARIABLE Result)
if(Result)
  execute_process(COMMAND ${CMAKE_COMMAND} -E copy
                      ${OriginalScript} ${CopiedScript})
  execute_process(COMMAND ${CMAKE_COMMAND} -E touch_nocreate ${FileToTouch})
endif()

The CMake script needs to have required variables passed in via the -D args before calling -P, so the calling CMakeLists.txt would have something like:

set(FileToTouch ${CMAKE_SOURCE_DIR}/src/main.cpp)

add_custom_target(CopyScript ALL ${CMAKE_COMMAND}
                      -DOriginalScript=${CMAKE_SOURCE_DIR}/my_script
                      -DCopiedScript=${CMAKE_BINARY_DIR}/my_script
                      -DFileToTouch=${FileToTouch}
                      -P ${CMAKE_SOURCE_DIR}/copy_script.cmake)

add_executable(MyExe ${FileToTouch})

This will cause a full rebuild of the executable, since it thinks a source file has been modified. If you only require to force relinking there may be a better way to achieve this.

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