Cmake series tutorial 2 HelloWorld

This article takes Windows System  Visual Studio  Based on the development environment , demonstration CMake structure HelloWorld course .

HelloWorld.cpp

New folder HelloWorld, newly build C++ Source code file HelloWorld.cpp, Write the code as follows ：HelloWorld.cpp

#include <stdio.h>
int main(int argc, char *argv[])
{
 printf("Hello World!\n");
 return 0;
}

CMakeLists.txt

With the HelloWorld.cpp Create a new folder CMake Script files CMakeLists.txt, Write the code as follows ：CMakeLists.txt

#  project name 
project(HelloWorld)
#  Output message at build time 
message(STATUS "This is HelloWorld project.")
#  Declare variables , Contains the source code files that need to be included in the current project 
set(SRC_FILES HelloWorld.cpp)
#  Build executable programs , You need to specify the source file of the executable program 
add_executable(HelloWorld ${SRC_FILES})

CMakeLists.txt  File is  CMake  Project organization script , There can only be one file per folder , The file name cannot be changed ,CMake  When building, it will find the... In the specified directory by default  CMakeLists.txt  File build .

Command specification

project（ Optional ）

Specify the current CMake Project name , This name is not Visual Studio The name of the project , This name does not affect the source code project name . If you use  Visual Studio  structure ,project  The name is the solution （*.sln） name . 
This parameter can be operated in some very convenient ways in complex projects , Later articles will explain in detail . 
If you're just building an ordinary simple project , This sentence can be omitted .

message（ Optional ）

message seeing the name of a thing one thinks of its function , It is the output message used by the project at ordinary times , stay CMake When building the project, output the message content specified by the parameter . 
CMake Didn't like IDE Same debugging method , When building a complex project, you need to judge whether the current construction project meets the expected parameter settings by outputting messages , Or output debugging information , Check that the configuration is correct .

The function prototype  

message([<mode>] "message to display" ...)

Common parameters

• FATAL_ERROR Fatal error , Terminate build . When this parameter is specified, the message is output , Description encountered an unhandled error , Stop building , Tell the developer where the error occurred .
• WARNING Warning . Output warning message , Continue building .
• STATUS state . One of the common types , Output status information .
• (none) or NOTICE news . One of the common types , The output message .

set（ Optional ）

Declare variables , Replace a set of values with a variable .

The function prototype  

set(<variable> <value>... [PARENT_SCOPE])

Usage method  
CMake Use by convention  ${}  How to reference variables , Such as declaring variables in code  SRC_FILES  Record the source file of the current project , Use when building executables  ${SRC_FILES}  How to reference variables . 
have access to message(STATUS “${SRC_FILES}”) View the content defined in the variable .

add_executable（ Mandatory ）

Add an executable program according to the specified source code ,CMake The source code project will be built according to the current instructions , Parameters 1 <name>  It's the name of the project , Is the key parameter of project construction , In complex projects, you need to modify the compilation options , Specify the link library , Set build events through  <name>  Association .

The function prototype  

add_executable(<name> [WIN32] [MACOSX_BUNDLE] [EXCLUDE_FROM_ALL] [source1] [source2 ...])

As noted above   Optional   The order is to make CMake The script is readable 、 Extensibility 、 Maintainability , But it's not necessary . 
If in a simple example code , You can put the above  CMakeLists.txt  Script reduction  add_executable(HelloWorld HelloWorld.cpp) , Can achieve the same effect , But this method is not recommended .

Official documents

This article only introduces the basic meaning and common methods of commands from a practical point of view , If you want to fully understand other uses of commands , Please see the CMake Official documents of .

• Local documents .CMake The installation directory \doc\cmake\html\index.html
• Online document .CMake Document center （https://cmake.org/cmake/help/v3.15/）

structure （Windows）

structure Visual Studio engineering

Create a folder for storing project files  build, The current file structure is as follows ：

│ CMakeLists.txt

│ HelloWorld.cpp

│

└─build

Use the command line prompt  cmd  Switch to  build  Catalog , perform  cmake .., The output build information is as follows ：

D:\cmake\HelloWorld\build>cmake ..

-- Building for: Visual Studio 14 2015

-- Selecting Windows SDK version to target Windows 10.0.17134.

-- The C compiler identification is MSVC 19.0.24210.0

-- The CXX compiler identification is MSVC 19.0.24210.0

-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/cl.exe

-- Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/cl.exe -- 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: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/cl.exe

-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/cl.exe -- works

-- Detecting CXX compiler ABI info

-- Detecting CXX compiler ABI info - done

-- Detecting CXX compile features

-- Detecting CXX compile features - done

-- This is HelloWorld project.

-- Configuring done

-- Generating done

-- Build files have been written to: D:/cmake/HelloWorld/build

From the output information, you can see the following information ：

• Compiler Version ：Building for: Visual Studio 14 2015, When no compiler version is specified ,CMake Automatically select an available compiler from the current environment to build ,Windows Development environment deployment  Visual Studio  The default choice is , When there are multiple versions of  Visual Studio  The latest version is selected by default . remarks ： Because this article builds the environment installation  Visual Studio 2015, The actual build is based on the current development environment  Visual Studio  The version shall prevail .
• message  Command output message  This is HelloWorld project.
• Storage directory of engineering documents ：D:/cmake/HelloWorld/build

In build command  ..  Indicates that the path of the specified source code is the upper level directory , It's also  CMakeLists.txt  File directory .

After building , stay  build  Directory generation  Visual Studio 2015  project ,

Specify parameters to build

Specify the build directory

When you need to specify the source code or build the build directory , have access to  -S  Specify the source directory ,-B  Specify the project build directory . 
CMake Examples of command line tool parameters ：cmake [options] -S <path-to-source> -B <path-to-build>

Specifies the compiler build

When a build environment deploys multiple development environments ,cmake Components can be through  -G"generator-name"  Specify compiler . 
for example ：

• structure NMake engineering  cmake -G"NMake Makefiles" ..
• structure VS2012 engineering ,cmake -G"Visual Studio 11 2012" ..

This article only lists two common construction parameters ,CMake Support build parameters. For details, use the command line prompt （CMD） Input  cmake --help  View details .

compile

This article USES the  Visual Studio  development environment , Therefore, using VS open HelloWorld.sln, Compile the source code to generate executable files .

Run the compiled program , Execution results ：

Hello World!

 Please press any key to continue . . .