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【NO.276】CMake基础 第14节 在文件中进行变量替换.md

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【NO.276】CMake基础 第14节 在文件中进行变量替换

1.介绍

在调用cmake期间，可以创建使用CMakeLists.txt和cmake缓存中的变量的文件。在cmake生成期间，文件被复制到新位置，并替换所有cmake变量。

本教程中的文件如下：

$ tree
.
├── CMakeLists.txt
├── main.cpp
├── path.h.in
├── ver.h.in

  • [CMakeLists.txt] - 包含要运行的CMake命令

    cmake_minimum_required(VERSION 3.5)

# Set the project name
project (cf_example)

# set a project version
set (cf_example_VERSION_MAJOR 0)
set (cf_example_VERSION_MINOR 2)
set (cf_example_VERSION_PATCH 1)
set (cf_example_VERSION "${cf_example_VERSION_MAJOR}.${cf_example_VERSION_MINOR}.${cf_example_VERSION_PATCH}")

# Call configure files on ver.h.in to set the version.
# Uses the standard ${VARIABLE} syntax in the file
configure_file(ver.h.in ${PROJECT_BINARY_DIR}/ver.h)

# configure the path.h.in file.
# This file can only use the @VARIABLE@ syntax in the file
configure_file(path.h.in ${PROJECT_BINARY_DIR}/path.h @ONLY)

# Add an executable
add_executable(cf_example
    main.cpp
)

# include the directory with the new files
target_include_directories( cf_example
    PUBLIC
        ${CMAKE_BINARY_DIR}
)

  • [main.cpp] - 具有main的源文件

    #include <iostream>
#include "ver.h"
#include "path.h"

int main(int argc, char *argv[])
{
    std::cout << "Hello Version " << ver << "!" << std::endl;
    std::cout << "Path is " << path << std::endl;
   return 0;
}

  • [path.h.in] - 包含构建目录路径的文件

    #ifndef __PATH_H__
#define __PATH_H__

// version variable that will be substituted by cmake
// This shows an example using the @ variable type
const char* path = "@CMAKE_SOURCE_DIR@";

#endif

  • [ver.h.in] - 包含项目版本的文件

    #ifndef __VER_H__
#define __VER_H__

// version variable that will be substituted by cmake
// This shows an example using the $ variable type
const char* ver = "${cf_example_VERSION}";

#endif

2.概念

2.1 配置文件

要在文件中进行变量替换，可以使用CMake中的configure_file()函数。此函数的核心参数是源文件和目标文件。

configure_file(ver.h.in ${PROJECT_BINARY_DIR}/ver.h)

configure_file(path.h.in ${PROJECT_BINARY_DIR}/path.h @ONLY)

上面的第一个示例允许使用像CMake变量一样的${}语法或ver.h.in文件中的@@定义变量。生成后，新文件ver.h将在PROJECT_BINARY_DIR中可用。

const char* ver = "${cf_example_VERSION}";

第二个示例只允许在path.h.in文件中使用@@语法定义变量。生成后，将在PROJECT_BINARY_DIR中提供新文件path.h。

const char* path = "@CMAKE_SOURCE_DIR@";

3.构建示例

$ mkdir build

$ cd build/

$ cmake ..
-- The C compiler identification is GNU 4.8.4
-- The CXX compiler identification is GNU 4.8.4
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/matrim/workspace/cmake-examples/03-code-generation/configure-files/build

$ ls
CMakeCache.txt  CMakeFiles  cmake_install.cmake  Makefile  path.h  ver.h

$ cat path.h
#ifndef __PATH_H__
#define __PATH_H__

// version variable that will be substituted by cmake
// This shows an example using the @ variable type
const char* path = "/home/matrim/workspace/cmake-examples/03-code-generation/configure-files";

#endif

$ cat ver.h
#ifndef __VER_H__
#define __VER_H__

// version variable that will be substituted by cmake
// This shows an example using the $ variable type
const char* ver = "0.2.1";

#endif

$ make
Scanning dependencies of target cf_example
[100%] Building CXX object CMakeFiles/cf_example.dir/main.cpp.o
Linking CXX executable cf_example
[100%] Built target cf_example

$ ./cf_example
Hello Version 0.2.1!
Path is /home/matrim/workspace/cmake-examples/03-code-generation/configure-files

原文作者：橘崽崽啊

原文链接：https://www.cnblogs.com/juzaizai/p/15069698.html