Cmake tutorial step1 (basic starting point)

CMake Official documents

Refer to the official cmake3.24 Course translation
https://cmake.org/cmake/help/v3.24/guide/tutorial/index.html
https://gitlab.kitware.com/cmake/cmake/-/tree/master/Help/guide/tutorial
step1
https://cmake.org/cmake/help/v3.24/guide/tutorial/A%20Basic%20Starting%20Point.html
My warehouse :
https://github.com/FRBoiling/cmake-tutorial.git

Basic starting point

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

Create project folder

Create project folder Step1, And enter

mkdir Step1
cd Step1

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 ）

vi tutorial.cxx

vi tutorial.cxx

// A simple program that computes the square root of a number
#include <cmath>
#include <cstdlib>
#include <iostream>
#include <string>

int main(int argc, char* argv[])
{
    
  if (argc < 2) {
    
    std::cout << "Usage: " << argv[0] << " number" << std::endl;
    return 1;
  }

  // convert input to double
  const double inputValue = atof(argv[1]);

  // calculate square root
  const double outputValue = sqrt(inputValue);
  std::cout << "The square root of " << inputValue << " is " << outputValue
            << std::endl;
  return 0;
}

To write CMakeLists.txt file

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

vi CMakeLists.txt

cmake_minimum_required(VERSION 3.10)

# set the project name
project(Tutorial)

# add the executable
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 .
Be careful , Only system instructions are case insensitive , But variables and strings are case sensitive

Build and run

2.1、 Create a build directory

cd ..
mkdir Step1_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 Step1_build
cmake ../Step1

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

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 3.10)

# # set the project name
# project(Tutorial)
# 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 .

# add the binary tree to the search path for include files so that we will find TutorialConfig.h
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 :

// A simple program that computes the square root of a number
#include <cmath>
#include <cstdlib>
#include <iostream>
#include <string>
#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;
  }

  // convert input to double
  // const double inputValue = atof(argv[1]);
  const double inputValue = std::stod(argv[1]);
  // calculate square root
  const double outputValue = sqrt(inputValue);
  std::cout << "The square root of " << inputValue << " is " << outputValue
            << std::endl;
  return 0;
}

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_minimum_required(VERSION 3.10)

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

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

# configure a header file to pass some of the CMake settings to the source code
configure_file(TutorialConfig.h.in TutorialConfig.h)

# add the executable
add_executable(Tutorial tutorial.cxx)

# add the binary tree to the search path for include files so that we will find TutorialConfig.h
target_include_directories(Tutorial PUBLIC
                           "${PROJECT_BINARY_DIR}"
                           )

Rebuild and test the changes

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