使用 CMake 从二进制文件编译和添加目标文件

Question

我正在用 C++ 编写一个 Excel 文件生成器。

我拥有工作所需的一切，但我仍然依赖于一个外部的空 .xlsx 文件，我根据需要解压缩、迭代并添加数据以创建最终文件。

我想通过将 .xlsx 文件转换为可执行文件的 .rodata 部分中的二进制 blob 来消除这种依赖关系，方法是先将其转换为像这样的目标文件：

$ ld -r -b binary -o template.o template.xlsx
$ objcopy --rename-section .data=.rodata,alloc,load,readonly,data,contents template.o template.o

我从博文 http://www.burtonini.com/blog/computers/ld-blobs-2007-07-13-15-50 中获得了这些信息。

第二步是将其链接到二进制文件中，我可以使用ld。

如何使用 CMake 自动执行这两个步骤？

目前我不知道如何在第一步运行特定命令，例如上面的ld，第二步我尝试将files/template.o 添加到我的target_link_libraries，但ld 只是说：

/usr/bin/ld: cannot find -lfiles/template.o

我在 CMakeLists.txt 中添加了以下自定义命令：

add_custom_command(OUTPUT files/template.o
      COMMAND ld -r -b binary -o files/template.o files/template.xlsx
      COMMAND objcopy --rename-section .data=.rodata,alloc,load,readonly,data,contents files/template.o files/template.o)

并将 files/template.o 添加到 add_executable 调用中。

不幸的是，CMake 是这样说的：

ld: 无法打开输出文件 files/template.o: 没有这样的文件或目录

据我了解，add_custom_command 中的 OUTPUT 命令允许我们告诉 CMake COMMAND 命令正在创建什么文件。所以我现在有点困惑。

我更新了 CMakeLists.txt 文件并添加了一个目标，以确保构建模板文件：

add_custom_target(run ALL
    DEPENDS template.o)

还有一个依赖项，以确保它在 excelbuilder 目标之前构建：

add_dependencies(excelbuilder run)

我还更新了自定义命令，如下所示：

add_custom_command(OUTPUT template.o
      COMMAND ld -r -b binary -o template.o ${CMAKE_CURRENT_SOURCE_DIR}/files/template.xlsx
      COMMAND objcopy --rename-section .data=.rodata,alloc,load,readonly,data,contents template.o template.o)

当我运行这个时，输出如下（make VERBOSE=1）

$ make VERBOSE=1
/usr/bin/cmake -H/home/ravloony/projects/excelparser -B/home/ravloony/projects/excelparser/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/ravloony/projects/excelparser/build/CMakeFiles /home/ravloony/projects/excelparser/build/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/ravloony/projects/excelparser/build'
make -f src/lib/minizip/CMakeFiles/minizip_1-1.dir/build.make src/lib/minizip/CMakeFiles/minizip_1-1.dir/depend
make[2]: Entering directory `/home/ravloony/projects/excelparser/build'
cd /home/ravloony/projects/excelparser/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/ravloony/projects/excelparser /home/ravloony/projects/excelparser/src/lib/minizip /home/ravloony/projects/excelparser/build /home/ravloony/projects/excelparser/build/src/lib/minizip /home/ravloony/projects/excelparser/build/src/lib/minizip/CMakeFiles/minizip_1-1.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/home/ravloony/projects/excelparser/build'
make -f src/lib/minizip/CMakeFiles/minizip_1-1.dir/build.make src/lib/minizip/CMakeFiles/minizip_1-1.dir/build
make[2]: Entering directory `/home/ravloony/projects/excelparser/build'
make[2]: Nothing to be done for `src/lib/minizip/CMakeFiles/minizip_1-1.dir/build'.
make[2]: Leaving directory `/home/ravloony/projects/excelparser/build'
/usr/bin/cmake -E cmake_progress_report /home/ravloony/projects/excelparser/build/CMakeFiles  17 18 19 20 21
[ 22%] Built target minizip_1-1
make -f CMakeFiles/run.dir/build.make CMakeFiles/run.dir/depend
make[2]: Entering directory `/home/ravloony/projects/excelparser/build'
cd /home/ravloony/projects/excelparser/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/ravloony/projects/excelparser /home/ravloony/projects/excelparser /home/ravloony/projects/excelparser/build /home/ravloony/projects/excelparser/build /home/ravloony/projects/excelparser/build/CMakeFiles/run.dir/DependInfo.cmake --color=
Dependee "/home/ravloony/projects/excelparser/build/CMakeFiles/run.dir/DependInfo.cmake" is newer than depender "/home/ravloony/projects/excelparser/build/CMakeFiles/run.dir/depend.internal".
Dependee "/home/ravloony/projects/excelparser/build/CMakeFiles/CMakeDirectoryInformation.cmake" is newer than depender "/home/ravloony/projects/excelparser/build/CMakeFiles/run.dir/depend.internal".
Scanning dependencies of target run
make[2]: Leaving directory `/home/ravloony/projects/excelparser/build'
make -f CMakeFiles/run.dir/build.make CMakeFiles/run.dir/build
make[2]: Entering directory `/home/ravloony/projects/excelparser/build'
/usr/bin/cmake -E cmake_progress_report /home/ravloony/projects/excelparser/build/CMakeFiles 22
[ 27%] Generating template.o
ld -r -b binary -o template.o /home/ravloony/projects/excelparser/files/template.xlsx
objcopy --rename-section .data=.rodata,alloc,load,readonly,data,contents template.o template.o
make[2]: Leaving directory `/home/ravloony/projects/excelparser/build'
/usr/bin/cmake -E cmake_progress_report /home/ravloony/projects/excelparser/build/CMakeFiles  22
[ 27%] Built target run
make -f CMakeFiles/excelbuilder.dir/build.make CMakeFiles/excelbuilder.dir/depend
make[2]: Entering directory `/home/ravloony/projects/excelparser/build'
cd /home/ravloony/projects/excelparser/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/ravloony/projects/excelparser /home/ravloony/projects/excelparser /home/ravloony/projects/excelparser/build /home/ravloony/projects/excelparser/build /home/ravloony/projects/excelparser/build/CMakeFiles/excelbuilder.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/home/ravloony/projects/excelparser/build'
make -f CMakeFiles/excelbuilder.dir/build.make CMakeFiles/excelbuilder.dir/build
make[2]: Entering directory `/home/ravloony/projects/excelparser/build'
Linking CXX executable excelbuilder
/usr/bin/cmake -E cmake_link_script CMakeFiles/excelbuilder.dir/link.txt --verbose=1
/usr/bin/c++   -std=c++0x  -g -ftest-coverage -fprofile-arcs -fpermissive    CMakeFiles/excelbuilder.dir/src/common/exception.cpp.o CMakeFiles/excelbuilder.dir/src/excelbuilder/retriever.cpp.o CMakeFiles/excelbuilder.dir/src/excelbuilder/xlsx.cpp.o CMakeFiles/excelbuilder.dir/src/common/config.cpp.o CMakeFiles/excelbuilder.dir/src/excelbuilder/main.cpp.o  -o excelbuilder -rdynamic src/lib/minizip/libminizip_1-1.so -ltinyxml2 -lmysqlcppconn -lboost_regex-mt -ltemplate.o -lz -Wl,-rpath,/home/ravloony/projects/excelparser/build/src/lib/minizip
/usr/bin/ld: cannot find -ltemplate.o
collect2: error: ld returned 1 exit status
make[2]: *** [excelbuilder] Error 1
make[2]: Leaving directory `/home/ravloony/projects/excelparser/build'
make[1]: *** [CMakeFiles/excelbuilder.dir/all] Error 2
make[1]: Leaving directory `/home/ravloony/projects/excelparser/build'
make: *** [all] Error 2

但是文件 template.o 已经正确生成并且在文件夹中。 ld 似乎在期待一个系统库。

Answer 1

最后，我就是这样做的。

add_custom_command(OUTPUT template.o
      COMMAND cd ${CMAKE_CURRENT_SOURCE_DIR}/files && ld -r -b binary -o ${CMAKE_CURRENT_BINARY_DIR}/template.o template.xlsx
      COMMAND objcopy --rename-section .data=.rodata,alloc,load,readonly,data,contents ${CMAKE_CURRENT_BINARY_DIR}/template.o ${CMAKE_CURRENT_BINARY_DIR}/template.o)

cd 命令之所以存在，是因为ld 将自动声明的变量的名称设置为取决于传递给输入文件的完整路径的名称。因此，如果输入文件是/home/user/project/files/template.xlsx，则变量将类似于_binary_home_user_project_files_template_xlsx_start。不适合便携编译。

add_library(template
        STATIC
        template.o)

告诉链接器将目标文件编译成二进制文件。这还会添加一个名为template 的目标。

然后

SET_SOURCE_FILES_PROPERTIES(
  template.o
  PROPERTIES
  EXTERNAL_OBJECT true
  GENERATED true
  )

告诉 CMake 不要编译在构建时生成的文件。

SET_TARGET_PROPERTIES(
  template
  PROPERTIES
  LINKER_LANGUAGE C 
  )

否则我们会收到一条错误消息，因为 CMake 无法从“.o”后缀中找出我们需要的 C 链接器。

然后在我的target_link_libraries 步骤中，我只是添加了template 作为目标。

target_link_libraries (excelbuilder
            ${MINIZIP_LIB_NAME}
            ${TINYXML_LIBRARIES}
            ${MYSQLCONNECTORCPP_LIBRARY}
            ${Boost_LIBRARIES}
            template
            )

Answer 2

要将目标文件链接到可执行文件，请将其添加到 add_executable() 的源文件列表中，而不是尝试将其添加到 target_link_libraries()。

首先要生成目标文件，请参阅add_custom_command()。在这种情况下，您将需要使用其指定 OUTPUT 参数的形式。