visual-studio - CMake - 仅当文件不存在时复制文件

Question

我想使用 cmake 将 postbuild 中的文件复制到构建目录，但前提是它们尚不存在。

我知道“add_custom_command”有一个“copy_if_different”开关，但我找不到类似“copy_if_doesnt_exist”的东西。

目前我坚持这个:

file(GLOB CONFIGURATION_DATA ${PROJECT_SOURCE_DIR}/data/configurations/*)

foreach(data ${CONFIGURATION_DATA})
    #only copy if file doesnt exists
    if(NOT EXISTS ?? how to get same path as - $<TARGET_FILE_DIR:${PROJECT_NAME_STR}>/data/configurations) )
        add_custom_command(TARGET ${PROJECT_NAME_STR} POST_BUILD 
        COMMAND ${CMAKE_COMMAND} -E copy 
        ${data}
        $<TARGET_FILE_DIR:${PROJECT_NAME_STR}>/data/configurations)
    endif()
endforeach()

我不知道如何获取目标文件路径的地方

$<TARGET_FILE_DIR:${PROJECT_NAME_STR}>/data/configurations

为了把它放到if语句中

Answer 1

对于不直接支持的情况，file(GENERATE ...)命令非常有用(因为它会评估 generator expressions )。

所以在您的情况下，我已经成功测试了以下代码示例:

cmake_minimum_required(VERSION 2.8.12)

if (POLICY CMP0070)
    cmake_policy(SET CMP0070 NEW)
endif()

project(CopyFileIfNotExists)

file(
    GENERATE 
        OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/CopyConfigurationData$<CONFIG>.cmake"
        CONTENT 
            "if (NOT EXISTS \"$<TARGET_FILE_DIR:${PROJECT_NAME}>/data/configurations\")
                execute_process(
                     COMMAND \"${CMAKE_COMMAND}\" -E copy_directory
                         \"${PROJECT_SOURCE_DIR}/data/configurations\"
                         \"$<TARGET_FILE_DIR:${PROJECT_NAME}>/data/configurations\"
                )
            endif()"
)

file(WRITE "main.cpp" "int main() { return 0; }")

add_executable(${PROJECT_NAME} "main.cpp")

add_custom_command(
    TARGET ${PROJECT_NAME} 
    POST_BUILD 
    COMMAND "${CMAKE_COMMAND}" -P "CopyConfigurationData$<CONFIG>.cmake"
    WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
)

备选

或者如果可以运行每个 CMake(重新)配置，只需添加以下内容而不是构建后步骤:

file(
    GLOB 
        CONFIGURATION_DATA 
        RELATIVE "${PROJECT_SOURCE_DIR}"
        "${PROJECT_SOURCE_DIR}/data/configurations/*"
 )

foreach(data IN LISTS CONFIGURATION_DATA)
    file(
        GENERATE 
            OUTPUT "$<TARGET_FILE_DIR:${PROJECT_NAME}>/${data}"
            INPUT  "${PROJECT_SOURCE_DIR}/${data}"
    )
endforeach()

替代方案:优化版本

利用file(COPY ...)我能想到的最短的基于脚本的版本也优化了现有的项目

"Copying preserves input file timestamps, and optimizes out a file if it exists at the destination with the same timestamp."

看起来像这样:

file(
    GENERATE 
        OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/CopyConfigurationData$<CONFIG>.cmake"
        CONTENT "file(
                    COPY \"${PROJECT_SOURCE_DIR}/data/configurations\"
                    DESTINATION \"$<TARGET_FILE_DIR:${PROJECT_NAME}>/data\"
                 )"
)