Question

I'm working on reducing build time for my project. In my top level CMakeLists.txt I add several external projects, e.g. googletest:

ExternalProject_Add(googletest
   PREFIX "${CMAKE_CURRENT_BINARY_DIR}/googletest"
   GIT_REPOSITORY https://github.com/google/googletest.git
   INSTALL_DIR "${CMAKE_BINARY_DIR}"
   CMAKE_ARGS "-DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}"
   )

When I recompile the project, googletest also recompiles or at least it takes about 15 second for being processed. I can avoid that by adding UPDATE_COMMAND "". Then goolgetest will not be recompiled and building is about 15s faster.

Ideally googletest would update, if e.g. the local clone wasn't updated for a day. That way I would not need to comment the UPDATE_COMMAND ""-line out for getting the latest version.

Is there a way to accomplish this automatically?

Answer 1

可以将当前日期存储在缓存变量中，并且只有在自上次cmake配置运行后更改日期时才更新googletest。

在cmake mailing list archive上找到了以下脚本中使用的“TODAY”宏。

macro (TODAY RESULT)
  if (WIN32)
    execute_process(COMMAND "date" "/T" OUTPUT_VARIABLE ${RESULT})
    string(REGEX REPLACE "(..)/(..)/..(..).*" "\\3\\2\\1"
      ${RESULT} ${${RESULT}})
  elseif(UNIX)
    execute_process(COMMAND "date" "+%d/%m/%Y" OUTPUT_VARIABLE ${RESULT})
    string(REGEX REPLACE "(..)/(..)/..(..).*" "\\3\\2\\1"
      ${RESULT} ${${RESULT}})
  else (WIN32)
    message(SEND_ERROR "date not implemented")
    set(${RESULT} 000000)
  endif (WIN32)
endmacro (TODAY)

TODAY(CURRENT_DATE)
message("Current date is: ${CURRENT_DATE}")

if(${PREVIOUS_CURRENT_DATE} AND ${PREVIOUS_CURRENT_DATE} STREQUAL ${CURRENT_DATE})
  message("Sorry. Googletest already updated today.")
else()
  message("Ok. It's first time today!")
  set(PREVIOUS_CURRENT_DATE ${CURRENT_DATE} CACHE INTERNAL "Current date")
  ExternalProject_Add(googletest
    PREFIX "${CMAKE_CURRENT_BINARY_DIR}/googletest"
    GIT_REPOSITORY https://github.com/google/googletest.git
    INSTALL_DIR "${CMAKE_BINARY_DIR}"
    CMAKE_ARGS "-DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}"
    )
endif()

如果更改了构建目录或删除了CMakeCache.txt，则缓存日期将丢失 - 在cmake配置/构建之后将更新googletest。

另请注意，仅在cmake配置步骤期间比较日期。因此，除非明确执行cmake配置或修改CMakeLists.txt，否则将跳过日期比较。

Answer 2

开箱即用，这是不可能的。也许您可以使用UPDATE_DISCONNECTED提出解决方法。

可能最好为CMake提交功能请求（并在此处共享）。我认为你的用例是有效的。

Instruct CMake's ExternalProject_Add to update only once a day?

2 个答案: