c++ - CMake:带有 PRE_BUILD 的 add_custom_command 不起作用

Question

在下面的 CMakeLists.txt 文件中，虽然我设置了一个带有 PRE_BUILD 选项的 add_custom_command 命令，但自定义命令并不总是在生成主要可执行文件之前执行:

cmake_minimum_required(VERSION 2.8)
project(VersioningTest)

set(MAJOR 1)
set(MINOR 0)
set(PATCH 0)

set(PRODUCT App-${MAJOR}-${MINOR}-${PATCH})

ADD_EXECUTABLE(${PRODUCT}
                main.cpp
                Engine.cpp)

add_custom_command(TARGET ${PRODUCT} PRE_BUILD
                COMMAND ${CMAKE_COMMAND}
                -DMAJOR=${MAJOR}
                -DMINOR=${MINOR}
                -DPATCH=${PATCH}
                -P ${CMAKE_SOURCE_DIR}/SetVersion.cmake
                WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
                COMMENT "setting version...")

所以我决定用 add_custom_target 和 add_dependencies 替换 add_custom_command:

add_custom_target(SetVersion
                COMMAND ${CMAKE_COMMAND}
                -DMAJOR=${MAJOR}
                -DMINOR=${MINOR}
                -DPATCH=${PATCH}
                -P ${CMAKE_SOURCE_DIR}/SetVersion.cmake
                WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
                COMMENT "setting version...")

add_dependencies(${PRODUCT} SetVersion)

它奏效了。现在 SetVersion.cmake 文件每次都在生成主可执行文件之前执行。我的 CMake 文件中的 add_custom_command 有什么问题？

SetVersion.cmake文件内容:

EXECUTE_PROCESS(
    COMMAND svn info ${CMAKE_SOURCE_DIR}
    COMMAND grep Revision
    OUTPUT_VARIABLE REVISION
    OUTPUT_STRIP_TRAILING_WHITESPACE
)

EXECUTE_PROCESS(
     COMMAND svn diff ${CMAKE_SOURCE_DIR}
     OUTPUT_VARIABLE SVNDIFF
     OUTPUT_STRIP_TRAILING_WHITESPACE
 )

if(SVNDIFF STREQUAL "")
    set(LOCALCHANGES 0)
    message("No local changes detected")
else(SVNDIFF STREQUAL "")
    set(LOCALCHANGES 1)
    message("Local changes detected!")
endif(SVNDIFF STREQUAL "")

configure_file(${CMAKE_SOURCE_DIR}/version.h.in ${CMAKE_SOURCE_DIR}/version.h)
message("Version set") # For testing only

以及version.h.in的内容:

#define MAJOR_VERSION "${MAJOR}"
#define MINOR_VERSION "${MINOR}"
#define PATCH_VERSION "${PATCH}"
#define REVISION "${REVISION}"
#define LOCALCHANGES "${LOCALCHANGES}"

Answer 1

这取决于您使用的 CMake 生成器。这是来自 add_custom_command 的相关部分文档:

Note that the PRE_BUILD option is only supported on Visual Studio 7 or later.
For all other generators PRE_BUILD will be treated as PRE_LINK.

在 OS X 下 PRE_BUILD 似乎也适用于 Xcode，但没有正确记录。