Cmake tutorial (I)

CMake Official documents

Refer to the official cmake3.24 Course translation . I'm going to use cmake 3.16 To demonstrate examples .
https://cmake.org/cmake/help/v3.24/guide/tutorial/A%20Basic%20Starting%20Point.html

1、 The starting point of the foundation

Build and run a basic project （ Executable files built from source code files ）, This will be the starting point of our tutorial .

1.1、 Create project folder

Create project folder rd-project, And enter

mkdir rd-project
cd rd-project

1.2、 Create source code file

Source code file tutorial.cxx, The content of the file is the same as the code for calculating the square root of the official tutorial tutorial.cxx （ stay cmake Source code Step1 The catalog provides ）

#include <stdio.h> 
#include <stdlib.h> 
#include <math.h> 
int main(int argc, char* argv[]){
     
    if(argc<2){
     
        fprintf(stdout, "Uage: %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; 
} 

1.3、 To write CMakeLists.txt file

stay Step1 Create a CMakeLists.txt file , The most basic project only needs one three lines CMakeLists.txt file .

vi CMakeLists.txt

# cmake edition  #  see cmake edition cmake --version  Used here 3.16
cmake_minimum_required(VERSION 3.16)

#  project name 
project(Tutorial) 

#   add to app The source file 
add_executable(Tutorial tutorial.cxx) 

Be careful , This example is in the CMakeLists.txt Lower case commands are used in the file .CMake Capital letters are supported 、 Lower case and mixed case commands .

2、 Build and run

2.1、 Create a build directory

cd ..
mkdir rd_build

2.2、 Generate a local build system

Go to the build directory and run CMake To configure the project and generate a local build system

cd rd_build
cmake ../rd-project

2.3、 Actual compilation / Link items

Build the system locally to actually compile / Link items :

cmake --build .

thus , Build compilation complete .

2.4、 Try running an executable

./Tutorial 4294967296
./Tutorial 10
./Tutorial

The operation results are as follows

3、 Add the version number and configurable header file to the project

The first feature we will add is to provide a version number for our executables and projects . Although we can do this alone in the source code , But use CMakeLists.txt Provides greater flexibility .

3.1、 Use project() Command to set the project name and version number

cmake_minimum_required(VERSION 3.16)

# set the project name and version
project(Tutorial VERSION 1.0)

3.2、 Configure a header file , Pass the version number to the source code

configure_file(TutorialConfig.h.in TutorialConfig.h)

3.3、 Because the configuration file will be written to the binary tree , We must add this directory to the path list to search for included files .

target_include_directories(Tutorial PUBLIC
                           "${PROJECT_BINARY_DIR}"
                           )

3.4、 Use your favorite editor , Create in the source directory TutorialConfig.h.in, Contains the following :

// the configured options and settings for [email protected]@ The referenced variables can be accessed through CMakeLists.txt To set up  
#define Tutorial_VERSION_MAJOR @[email protected]
#define Tutorial_VERSION_MINOR @[email protected]

When CMake When configuring this header file ,@[email protected] and @[email protected] The value of will be replaced .
tutorial.cxx Contains the configuration header file TutorialConfig.h
to update tutorial.cxx Source code , Print out the name and version number of the executable .cxx The contents are as follows :

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include "TutorialConfig.h" 

int main(int argc, char *argv[]) {
    
  if (argc < 2) {
    
    // report version
    std::cout << argv[0] << " Version " << Tutorial_VERSION_MAJOR << "."
              << Tutorial_VERSION_MINOR << std::endl;
    std::cout << "Usage: " << argv[0] << " number" << std::endl;
    return 1;
  }

// double inputValue = atof(argv[1]);
  const double inputValue = std::stod(argv[1]);
  double outputValue = sqrt(inputValue);
  fprintf(stdout, "The square root of %g is %g\n", inputValue, outputValue);
  return 0;
}

4、 Appoint c++ standard

Next , Let us in tutorial.cxx Lieutenant general atof Replace with std::stod, Add some... To our project c++ 11 characteristic . meanwhile , Delete
#include .

// file tutorial.cxx

// double inputValue = atof(argv[1]);
  const double inputValue = std::stod(argv[1]);

We need to be in CMake The code explicitly declares the correct standards it should use .
stay CMake Enable access to specific c++ The simplest way to support standards is to use CMAKE_CXX_STANDARD Variable .
In this tutorial , take cmakellists .txt In the document CMAKE_CXX_STANDARD The variable is set to 11, And will CMAKE_CXX_STANDARD_REQUIRED Set to True.
You have to make sure you're in add_executable Added... Above the call CMAKE_CXX_STANDARD Statement .
Tutorial to this point , complete CMakeLists.txt The contents are as follows ：

# cmake edition  #  see cmake edition cmake --version  Used here 3.16
cmake_minimum_required(VERSION 3.16)

# specify the C++ standard
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED True)

#  project name 
# project(Tutorial) 
# set the project name and version
project(Tutorial VERSION 1.0)

#   add to app The source file 
add_executable(Tutorial tutorial.cxx) 

#  The configuration file 
configure_file(TutorialConfig.h.in TutorialConfig.h)

target_include_directories(Tutorial PUBLIC
                           "${PROJECT_BINARY_DIR}"
                           )

5、 Rebuild and test the changes

Refer to the above steps 2.2 To 2.4 refactoring , And try to run the executable , Observe changes