c++ - Cmake 重新生成变量变化

Question

Y 部分:

我有一个运行外部程序并创建项目特定变量的 CMake 宏。我想让 CMake 做的是在每次构建时运行此脚本，检查变量是否已更改，如果它们已更改(以防止在未更改时重建完整项目)，则重新生成 CONFIGURE_FILE header ...我'不过我不太确定该怎么做。 (Add custom target每次都会重新构建头文件，不能调用宏，同Add Custom Command)。

X部分:

所以我编写了以下脚本来提取 hg 版本信息以用于 C++ 项目:

macro (ReadProjectRevisionStatus)
exec_program(hg ${PROJECT_SOURCE_DIR} ARGS paths OUTPUT_VARIABLE ${PROJECT_NAME}_HGPATHS)
message(STATUS "${PROJECT_NAME}_HGPATHS=${${PROJECT_NAME}_HGPATHS}}")
if (NOT(${PROJECT_NAME}_HGPATHS STREQUAL ""))

string(REPLACE "\n" ";" ${PROJECT_NAME}_HGPATHS ${${PROJECT_NAME}_HGPATHS})

foreach(HGPATH ${${PROJECT_NAME}_HGPATHS})
string(SUBSTRING "${HGPATH}" 0 10 HGPATHSTART)
if (HGPATHSTART MATCHES "default = ")
string(LENGTH "${HGPATH}" HGPATHLENGTH)
math(EXPR HGSUBLEN "${HGPATHLENGTH}-10")
string(SUBSTRING "${HGPATH}" 10 ${HGSUBLEN} ${PROJECT_NAME}_HGREMOTEDIR)
endif()
endforeach()

endif()

if (NOT ${PROJECT_NAME}_HGREMOTEDIR)
message(WARNING "No remote repository set. Will use current direcoty for build number, but this value may be inaccurate.")
set(${PROJECT_NAME}_HGREMOTEDIR ${PROJECT_SOURCE_DIR})
else()
exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR} ARGS status RETURN_VALUE HGREMOTESTATUSVALUE OUTPUT_VARIABLE NUL)
if (NOT HGREMOTESTATUSVALUE EQUAL 0)
message(WARNING "Cannot connect to remote repository at ${${PROJECT_NAME}_HGREMOTEDIR}. Will use current direcoty for build number, but this value may be inaccurate.")
set(${PROJECT_NAME}_HGREMOTEDIR ${PROJECT_SOURCE_DIR})
endif()
endif()

#Identify changeset
exec_program(hg ${PROJECT_SOURCE_DIR} ARGS "id" "-i" OUTPUT_VARIABLE OUTPUT_VARIABLE ${PROJECT_NAME}_HGHASHCODE)

if (${PROJECT_NAME}_HGHASHCODE MATCHES ".*\\+")
MESSAGE(STATUS "Node is dirty. Will generate temporary version number...")
set (${PROJECT_NAME}_HGDIRTY 1)
string(LENGTH ${${PROJECT_NAME}_HGHASHCODE} HGHASHLEN)
MATH(EXPR HGHASHLEN "${HGHASHLEN}-1")
string(SUBSTRING ${${PROJECT_NAME}_HGHASHCODE} 0 ${HGHASHLEN} ${PROJECT_NAME}_HGHASHCODE)
endif()
#check if remote repository contains changeset
exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR}
ARGS "log" "-r" "${${PROJECT_NAME}_HGHASHCODE}"
RETURN_VALUE HGREMOTEHASCHANGESET
OUTPUT_VARIABLE NUL)
if (NOT HGREMOTEHASCHANGESET EQUAL 0)
message(WARNING "Remote repository ${${PROJECT_NAME}_HGREMOTEDIR} does not have changeset ${${PROJECT_NAME}_HGHASHCODE}. Will use current direcoty for build number, but this value may be inaccurate.")
set(${PROJECT_NAME}_HGREMOTEDIR ${PROJECT_SOURCE_DIR})
endif()

exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR}
ARGS "log" "-r" ${${PROJECT_NAME}_HGHASHCODE} "--template" "{latesttag}"
OUTPUT_VARIABLE ${PROJECT_NAME}_HGMAJORMINORVERSION)

MESSAGE(STATUS "${PROJECT_NAME}_HGMAJORMINORVERSION=${${PROJECT_NAME}_HGMAJORMINORVERSION}")

exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR} 
ARGS "log" "-r" ${${PROJECT_NAME}_HGHASHCODE} "--template" "{latesttagdistance}"
 OUTPUT_VARIABLE ${PROJECT_NAME}_HGBUILDNUMBER)

if (${PROJECT_NAME}_HGDIRTY)
MATH(EXPR ${PROJECT_NAME}_HGBUILDNUMBER "${${PROJECT_NAME}_HGBUILDNUMBER}+1")
set(${PROJECT_NAME}_HGHASHCODE "${${PROJECT_NAME}_HGHASHCODE}+")
endif()

MESSAGE(STATUS "Version=${${PROJECT_NAME}_HGMAJORMINORVERSION}.${${PROJECT_NAME}_HGBUILDNUMBER}.${${PROJECT_NAME}_HGHASHCODE}")
endmacro()

我现在这样调用它。

ReadProjectRevisionStatus()
CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/main.h.in ${CMAKE_CURRENT_BINARY_DIR}/main.h)

main.h.in 在哪里:

#ifndef MAIN_H
#define MAIN_H
#include <string>

const std::string ${PROJECT_NAME}_HGMAJORMINORVERSION = "${${PROJECT_NAME}_HGMAJORMINORVERSION}";
const std::string ${PROJECT_NAME}_HGBUILDNUMBER = "${${PROJECT_NAME}_HGBUILDNUMBER}";
const std::string ${PROJECT_NAME}_HGHASHCODE = "${${PROJECT_NAME}_HGHASHCODE}";

const std::string ${PROJECT_NAME}_HG_SHORT_VERSION = 
    ${PROJECT_NAME}_HGMAJORMINORVERSION+"."+
    ${PROJECT_NAME}_HGBUILDNUMBER;

const std::string ${PROJECT_NAME}_HG_VERSION = 
    ${PROJECT_NAME}_HG_SHORT_VERSION + "." +
    ${PROJECT_NAME}_HGHASHCODE;

#endif

我想做的是在每个构建命令上运行这个宏(我可以使用 ADD_CUSTOM_TARGET 然后设置变量而不是从项目中读取它们)，但我只想重新生成 main.h 如果变量有更改(以防止不必要的重新编译)。

编辑:工作解决方案

做了一个HGVersion.CMake

cmake_minimum_required (VERSION 2.8)

macro (ReadProjectRevisionStatus)
message(STATUS PROJECT_SOURCE_DIR=${PROJECT_SOURCE_DIR})

exec_program(hg ${PROJECT_SOURCE_DIR} ARGS paths OUTPUT_VARIABLE ${PROJECT_NAME}_HGPATHS)
message(STATUS "${PROJECT_NAME}_HGPATHS=${${PROJECT_NAME}_HGPATHS}}")
if (NOT(${PROJECT_NAME}_HGPATHS STREQUAL ""))

string(REPLACE "\n" ";" ${PROJECT_NAME}_HGPATHS ${${PROJECT_NAME}_HGPATHS})

foreach(HGPATH ${${PROJECT_NAME}_HGPATHS})
string(SUBSTRING "${HGPATH}" 0 10 HGPATHSTART)
if (HGPATHSTART MATCHES "default = ")
string(LENGTH "${HGPATH}" HGPATHLENGTH)
math(EXPR HGSUBLEN "${HGPATHLENGTH}-10")
string(SUBSTRING "${HGPATH}" 10 ${HGSUBLEN} ${PROJECT_NAME}_HGREMOTEDIR)
endif()
endforeach()

endif()

if (NOT ${PROJECT_NAME}_HGREMOTEDIR)
message(WARNING "No remote repository set. Will use current direcoty for build number, but this value may be inaccurate.")
set(${PROJECT_NAME}_HGREMOTEDIR ${PROJECT_SOURCE_DIR})
else()
exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR} ARGS status RETURN_VALUE HGREMOTESTATUSVALUE OUTPUT_VARIABLE NUL)
if (NOT HGREMOTESTATUSVALUE EQUAL 0)
message(WARNING "Cannot connect to remote repository at ${${PROJECT_NAME}_HGREMOTEDIR}. Will use current direcoty for build number, but this value may be inaccurate.")
set(${PROJECT_NAME}_HGREMOTEDIR ${PROJECT_SOURCE_DIR})
endif()
endif()

#Identify changeset
exec_program(hg ${PROJECT_SOURCE_DIR} ARGS "id" "-i" OUTPUT_VARIABLE OUTPUT_VARIABLE ${PROJECT_NAME}_HGHASHCODE)

if (${PROJECT_NAME}_HGHASHCODE MATCHES ".*\\+")
MESSAGE(STATUS "Node is dirty. Will generate temporary version number...")
set (${PROJECT_NAME}_HGDIRTY 1)
string(LENGTH ${${PROJECT_NAME}_HGHASHCODE} HGHASHLEN)
MATH(EXPR HGHASHLEN "${HGHASHLEN}-1")
string(SUBSTRING ${${PROJECT_NAME}_HGHASHCODE} 0 ${HGHASHLEN} ${PROJECT_NAME}_HGHASHCODE)
endif()
#check if remote repository contains changeset
exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR}
ARGS "log" "-r" "${${PROJECT_NAME}_HGHASHCODE}"
RETURN_VALUE HGREMOTEHASCHANGESET
OUTPUT_VARIABLE NUL)
if (NOT HGREMOTEHASCHANGESET EQUAL 0)
message(WARNING "Remote repository ${${PROJECT_NAME}_HGREMOTEDIR} does not have changeset ${${PROJECT_NAME}_HGHASHCODE}. Will use current direcoty for build number, but this value may be inaccurate.")
set(${PROJECT_NAME}_HGREMOTEDIR ${PROJECT_SOURCE_DIR})
endif()

exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR}
ARGS "log" "-r" ${${PROJECT_NAME}_HGHASHCODE} "--template" "{latesttag}"
OUTPUT_VARIABLE ${PROJECT_NAME}_HGMAJORMINORVERSION)

MESSAGE(STATUS "${PROJECT_NAME}_HGMAJORMINORVERSION=${${PROJECT_NAME}_HGMAJORMINORVERSION}")

exec_program(hg ${${PROJECT_NAME}_HGREMOTEDIR} 
ARGS "log" "-r" ${${PROJECT_NAME}_HGHASHCODE} "--template" "{latesttagdistance}"
 OUTPUT_VARIABLE ${PROJECT_NAME}_HGBUILDNUMBER)

if (${PROJECT_NAME}_HGDIRTY)
MATH(EXPR ${PROJECT_NAME}_HGBUILDNUMBER "${${PROJECT_NAME}_HGBUILDNUMBER}+1")
set(${PROJECT_NAME}_HGHASHCODE "${${PROJECT_NAME}_HGHASHCODE}+")
endif()

MESSAGE(STATUS "Version=${${PROJECT_NAME}_HGMAJORMINORVERSION}.${${PROJECT_NAME}_HGBUILDNUMBER}.${${PROJECT_NAME}_HGHASHCODE}")
endmacro()
message(STATUS "GETTING HG VERSION")
ReadProjectRevisionStatus()
CONFIGURE_FILE(${PROJECT_SOURCE_DIR}/main.h.in ${PROJECT_BINARY_DIR}/main.h)

在主 cmake 文件中

add_custom_target(
${PROJECT_NAME}_hg_version_target
 DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/main.h.in
 COMMAND ${CMAKE_COMMAND}
 ARGS -DPROJECT_SOURCE_DIR=${PROJECT_SOURCE_DIR}
 -DPROJECT_NAME=${PROJECT_NAME}
 -DPROJECT_BINARY_DIR=${PROJECT_BINARY_DIR}
 -P "${CMAKE_CURRENT_SOURCE_DIR}/HGVersion.CMake")

和

添加依赖项(${PROJECT_NAME} ${PROJECT_NAME}_hg_version_target)

有效但看起来...真的很乱。有人有更好的东西吗？

Answer 1

如果构建过程中的某些东西决定了要生成的文件的内容，则不能使用 configure_file 生成该文件，因为 configure_file 在配置阶段运行，而不是在构建时运行。这是 CMake 的设计选择。

在您的情况下，正如您已经发现的那样，您确实必须在构建过程中使用 add_custom_command 和 add_custom_target 来生成该文件。

对于您提出的解决方案，可能有机会稍微简化一下。在生成 C/C++ 头文件时，CMake 内部解析器应该能够自动发现哪些常用源代码文件依赖于 main.h。因此，使用 add_custom_command 提供自定义命令就足够了，它声明将生成的 main.h 文件作为其 OUTPUT。一旦 CMake 尝试构建一个 C/C++ 文件依赖于它的目标，CMake 应该会自动调用此命令。所以您可能不需要自定义目标和手动声明的依赖项。