CMake实战

2019-03-13 本文已影响17人 konishi5202

本文不介绍cmake命令使用方法，也不讲CMakeLists.txt的语法，有需要的读者可以看我另外相关的文章即可（此为实战篇）。

本文核心讲解添加版本支持、添加编译库支持、添加编译选项支持、添加库版本信息、添加多文件支持、添加安装路劲支持、添加测试验证支持、添加依赖函数与头文件与库文件支持、添加三方库依赖搜索支持、添加生成中间文件支持、添加生成发行版本安装包支持等功能。

本文共分14章，为了便于学习，内容组织如下：

前面1~7章为基本常用方法，可满足大部分项目需求；
接下来三（8~10）章节非常简单，用于支持依赖的检测，便于学习人员歇口气；
后面的11~14章为高级功能，可以查询未知依赖、生成中间依赖文件，还可以制作标准的安装包。

废话少说，直接上主菜（复杂的解释也略过了）。有需要的，可以联系我获取每章节的实例。

一、基本工程

最简单的工程是编译一个源文件，并生成一个可执行文件。CMakeLists.txt仅仅只需要3行：


cmake_minimum_required(VERSION 2.8)

project(Tutorial)

add_executable(Tutorial tutorial.cxx)

对应的tutorial.cxx源码用于计算输入数据的平方根：


// A simple program that computes the suqare root of a number

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

int main(int argc, char *argv[])

{

if (argc < 2)

{

fprintf(stdout, "Usage: %s number\n", argv[0]);

return 1;

}

double inputValue = atof(argv[1]);

double outputValue = sqrt(inputValue);

fprintf(stdout, "The square root of %g is %g\n", inputValue, outputValue);

return 0;

}

将tutorial.cxx与CMakeLists.txt放在同一目录，创建build目录，并编译、运行，结果如下：


$ mkdir build

$ ls

build  CMakeLists.txt  tutorial.cxx

$ cd build/

$ cmake ..

-- The C compiler identification is GNU 4.8.5

-- The CXX compiler identification is GNU 4.8.5

-- 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

-- Detecting C compile features

-- Detecting C compile features - 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

-- Detecting CXX compile features

-- Detecting CXX compile features - done

-- Configuring done

-- Generating done

-- Build files have been written to: /work/study/Studied_Module/Module/cmake/basic_point/build

$ make

Scanning dependencies of target Tutorial

[ 50%] Building CXX object CMakeFiles/Tutorial.dir/tutorial.cxx.o

[100%] Linking CXX executable Tutorial

[100%] Built target Tutorial

$ ./Tutorial

Usage: ./Tutorial number

$ ./Tutorial 9

The square root of 9 is 3

二、添加配置头文件

有时候我们需要为我们的代码添加版本信息，或者其他相关的配置信息。我们当然可以通过直接添加配置的头文件来实现，不过通过CMakeLists.txt来实现会更加的灵活。下面是基于前面例子实现添加版本信息的CMakeLists.txt：


cmake_minimum_required(VERSION 2.8)

project(Tutorial)

# The version number

set (Tutorial_VERSION_MAJOR 1)

set (Tutorial_VERSION_MINOR 0)

# configure a header file to pass some of the CMake settings

# to the source code

configure_file (

"${PROJECT_SOURCE_DIR}/TutorialConfig.h.in"

"${PROJECT_BINARY_DIR}/TutorialConfig.h"

)

# add the binary tree to the search path for include files

# so that we will find TutorialConfig.h

include_directories("${PROJECT_BINARY_DIR}")

# add the executable

add_executable(Tutorial tutorial.cxx)

上面指定TutorialConfig.h由TutorialConfig.h.in文件生成。TutorialConfig.h.in的内容如下：


// the configured options and settings for Tutorial

#define Tutorial_VERSION_MAJOR @Tutorial_VERSION_MAJOR@

#define Tutorial_VERSION_MINOR @Tutorial_VERSION_MINOR@

当CMake配置这个头文件时，@Tutorial_VERSION_MAJOR@和@Tutorial_VERSION_MINOR@的值将被CMakeLists.txt文件中的值替换（注意两边的名字要一致）。

接下来我们修改tutorial.cxx源码，看是如何使用CMakeLists.txt定义的版本的：


// A simple program that computes the suqare root of a number

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include "TutorialConfig.h"

int main(int argc, char *argv[])

{

if (argc < 2)

{

fprintf(stdout, "%s Version %d.%d\n", argv[0],

Tutorial_VERSION_MAJOR, Tutorial_VERSION_MINOR);

fprintf(stdout, "Usage: %s number\n", argv[0]);

return 1;

}

double inputValue = atof(argv[1]);

double outputValue = sqrt(inputValue);

fprintf(stdout, "The square root of %g is %g\n", inputValue, outputValue);

return 0;

}

建立build目录，再次编译结果如下：


$ mkdir build

$ ls

build  CMakeLists.txt  TutorialConfig.h.in  tutorial.cxx

$ cd build/

$ cmake ..

-- The C compiler identification is GNU 4.8.5

-- The CXX compiler identification is GNU 4.8.5

-- 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

-- Detecting C compile features

-- Detecting C compile features - 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

-- Detecting CXX compile features

-- Detecting CXX compile features - done

-- Configuring done

-- Generating done

-- Build files have been written to: /work/study/Studied_Module/Module/cmake/basic_version/build

$ make

Scanning dependencies of target Tutorial

[ 50%] Building CXX object CMakeFiles/Tutorial.dir/tutorial.cxx.o

[100%] Linking CXX executable Tutorial

[100%] Built target Tutorial

$ ./Tutorial

./Tutorial Version 1.0

Usage: ./Tutorial number

$ ./Tutorial 16

The square root of 16 is 4

总结：添加配置头文件的流程如下：

在CMakeLists.txt中通过set命令设置自己命名的变量；
添加配置文件说明：


configure_file (

"${PROJECT_SOURCE_DIR}/TutorialConfig.h.in"

"${PROJECT_BINARY_DIR}/TutorialConfig.h"

)

创建配置文件*.h.in，并使用@variable@来访问第一步在CMakeLists.txt通过set定义的变量，使用C/C++的标准#define来定义；
在C/C++源码中通过include包含编译生成的配置头文件；
在C/C++源码中直接使用#define宏定义的名称。

三、添加一个库

继续基于前面的实例，我们将计算平方根的方法提取出来，做成一个mysqrt.cxx源文件库放在MathFunctions目录，我们提供的算法名称为mysqrt()。源码如下：


$ cd MathFunctions/

$ cat mysqrt.h

#ifndef MYSQRT_H__

#define MYSQRT_H__

double mysqrt(double x);

#endif

$ cat mysqrt.cxx

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

double mysqrt(double x)

{

double g = x;

while(fabs(g*g - x) > 0.000001)

{

g = (g+x/g)/2;

}

return g;

}

在MathFunctions目录中添加子CMakeLists.txt，编译生成库文件：


$ cat CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

project(MathFunctions)

add_library(MathFunctions SHARED mysqrt.cxx)

接下来修改顶层CMakeLists.txt，添加子目录MathFunctions的编译支持，添加头文件依赖路径，并添加依赖的库说明：


include_directories("${PROJECT_SOURCE_DIR}/MathFunctions")

add_library(MathFuncions)

# add the executable

add_executable(Tutorial tutorial.cxx)

add_link_libraries(Tutorial MathFunctions)

最后，修改tutorial.cxx源码，添加代码调用我们自己的mysqrt()函数（这里同时调用，还可以验证我们的算法是否正确）：


    double inputValue = atof(argv[1]);

double outputValue = sqrt(inputValue);

fprintf(stdout, "The square root of %g is %g\n", inputValue, outputValue);

outputValue = mysqrt(inputValue);

fprintf(stdout, "The square root of %g is %g\n", inputValue, outputValue);

四、添加编译选项

继续接着前面的实例，我们添加了自己的mysqrt()函数，但是我们并不一定都是使用自己的mysqrt()函数，当系统提供了sqrt()时，我们肯定希望调用系统标准的函数。也就是说，我们需要根据系统情况，动态选择调用方法。

我们当然可以通过在头文件中添加编译选项来实现，不过通过CMakeLists.txt来实现将更加灵活有趣。

首先，我们定义一个编译宏USE_MYMATH（在顶层CMakeLists.txt）：


# should we use our own math functions ?

option(USE_MYMATH

    "Use tutorial provided math implementation" ON)

这将告诉CMake默认打开USE_MYMATH，当然也可以通过ccmake或者编译选项来重新配置。接下来我们在顶层CMakeLists.txt同时添加依赖库的说明：


# add the MathFunctions library ?

#

if (USE_MYMATH)

    include_directories("${PROJECT_SOURCE_DIR}/MathFunctions")

    add_subdirectory(MathFunctions)

    set(EXTRA_LIBS ${EXTRA_LIBS} MathFunctions)

#endif(USE_MYMATH)

# add the executable

add_executable(Tutorial tutorial.cxx)

target_link_libraries(Tutorial ${EXTRA_LIBS})

注意：上面添加的USE_MYMATH选项的option命令，必须在configure_file命令之前，否则其默认ON的配置将会无效。

接下来，修改tutorial.cxx源代码，添加条件编译代码：


// A simple program that computes the suqare root of a number

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include "TutorialConfig.h"

#ifdef USE_MYMATH

#include "mysqrt.h"

#endif

int main(int argc, char *argv[])

{

if (argc < 2)

{

fprintf(stdout, "%s Version %d.%d\n", argv[0],

Tutorial_VERSION_MAJOR, Tutorial_VERSION_MINOR);

fprintf(stdout, "Usage: %s number\n", argv[0]);

return 1;

}

double inputValue = atof(argv[1]);

#ifdef USE_MYMATH

double outputValue = mysqrt(inputValue);

fprintf(stdout, "The square root of %g is %g(use tutorial mysqrt())\n", inputValue, outputValue);

#else

double outputValue = sqrt(inputValue);

fprintf(stdout, "The square root of %g is %g(use system sqrt())\n", inputValue, outputValue);

#endif

return 0;

}

最后，在TutorialConfig.h.in中添加支持，以便在CMake命令行传入不同的编译选项时生成不同的TutorialConfig.h文件：


#cmakedefine USE_MYMATH

创建build目录，并编译验证结果如下：

使用mysqrt()：


$ mkdir build

$ ls

build  CMakeLists.txt  MathFunctions  TutorialConfig.h.in  tutorial.cxx

$ cd build/

[study@konishi build]$ cmake -DUSE_MYMATH=True ..

-- The C compiler identification is GNU 4.8.5

-- The CXX compiler identification is GNU 4.8.5

-- 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

-- Detecting C compile features

-- Detecting C compile features - 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

-- Detecting CXX compile features

-- Detecting CXX compile features - done

-- Configuring done

-- Generating done

-- Build files have been written to: /work/study/Studied_Module/Module/cmake/04_basic_options/build

$ make

Scanning dependencies of target MathFunctions

[ 25%] Building CXX object MathFunctions/CMakeFiles/MathFunctions.dir/mysqrt.cxx.o

[ 50%] Linking CXX shared library libMathFunctions.so

[ 50%] Built target MathFunctions

Scanning dependencies of target Tutorial

[ 75%] Building CXX object CMakeFiles/Tutorial.dir/tutorial.cxx.o

[100%] Linking CXX executable Tutorial

[100%] Built target Tutorial

$ ./Tutorial

./Tutorial Version 1.0

Usage: ./Tutorial number

$ ./Tutorial  12

The square root of 12 is 3.4641(use tutorial mysqrt())

使用系统的sqrt()：


$ mkdir build

$ ls

build  CMakeLists.txt  MathFunctions  TutorialConfig.h.in  tutorial.cxx

$ cd build/

$ cmake -DUSE_MYMATH=False ..

-- The C compiler identification is GNU 4.8.5

-- The CXX compiler identification is GNU 4.8.5

-- 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

-- Detecting C compile features

-- Detecting C compile features - 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

-- Detecting CXX compile features

-- Detecting CXX compile features - done

-- Configuring done

-- Generating done

-- Build files have been written to: /work/study/Studied_Module/Module/cmake/04_basic_options/build

$ make

Scanning dependencies of target Tutorial

[ 50%] Building CXX object CMakeFiles/Tutorial.dir/tutorial.cxx.o

[100%] Linking CXX executable Tutorial

[100%] Built target Tutorial

[study@konishi build]$ ./Tutorial

./Tutorial Version 1.0

Usage: ./Tutorial number

$ ./Tutorial 13

The square root of 13 is 3.60555(use system sqrt())

总结：添加配置选项的流程如下：

CMake实战

一、基本工程

二、添加配置头文件

三、添加一个库

四、添加编译选项

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