work environment

• System: macOS Mojave 10.14.6
• CMake: Version 3.15.0-rc4

Hello,World! Extension - The same directory, multiple source files

(1) Create a new hello directory, create files CMakeLists.txt, main.cpp, MathFunctions.h, MathFunctions.cpp

$ mkdir hello
$ cd hello
$ touch CMakeLists.txt main.cpp MathFunctions.h MathFunctions.cpp
$ ll
-rw-r--r--  1 staff  staff   124B  8 14 17:19 CMakeLists.txt
-rw-r--r--  1 staff  staff     0B  8 15 16:22 MathFunctions.cpp
-rw-r--r--  1 staff  staff     0B  8 15 16:22 MathFunctions.h
-rw-r--r--@ 1 staff  staff   145B  8 14 21:33 main.cpp

(2) Writing MathFunctions.h

int power(int base, int exponent);

(3) Writing MathFunctions.cpp

#include <stdio.h>
#include <stdlib.h>
#include "MathFunctions.h"

int power(int base, int exponent) {
    int result = base;
    int i;

    if (exponent == 0) {
        return 1;
    }

    for(i = 1; i < exponent; ++i){
        result = result * base;
    }
    return result;
}

(4) Writing main.cpp

#include <iostream>
#include "MathFunctions.h"

using namespace std;

int main(int argc, char const *argv[]) {
  /* code */
  // cout << "Hello,World!" << power(2, 3) << endl;
  printf("%s power(2,3)=%d \n", "Hello,World!", power(2, 3));
  return 0;
}

(5) Writing CMakeLists.txt

# CMake Minimum Version Number Requirements
cmake_minimum_required(VERSION 3.15.0)

# Project name
project(hello)

# Find all source files in the current directory and save the name to the SRC_LIST variable
# set(SRC_LIST main.cpp MathFunctions.h MathFunctions.cpp)
aux_source_directory(. SRC_LIST)

# Specify a build target
add_executable(hello ${SRC_LIST})

(6) Compile and run

$ mkdir build
$ cd build
$ pwd
/Users/staff/Desktop/hello/build

$ cmake ..
-- The C compiler identification is AppleClang 10.0.1.10010046
-- The CXX compiler identification is AppleClang 10.0.1.10010046
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/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: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/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: /Users/staff/Desktop/hello/build

$ make
Scanning dependencies of target hello
[ 33%] Building CXX object CMakeFiles/hello.dir/MathFunctions.cpp.o
[ 66%] Building CXX object CMakeFiles/hello.dir/main.cpp.o
[100%] Linking CXX executable hello
[100%] Built target hello

$ ./hello
Hello,World! power(2,3)=8

Hello,World! Extension - Multiple directories, multiple source files

(1) Create a new hello directory, create files CMakeLists.txt, main.cpp, math/MathFunctions.h, math/MathFunctions.cpp

$ mkdir hello
$ cd hello
$ mkdir math
$ touch CMakeLists.txt main.cpp math/MathFunctions.h math/MathFunctions.cpp
$ tree
.
├── CMakeLists.txt
├── main.cpp
└── math
    ├── MathFunctions.cpp
    └── MathFunctions.h

(2) Coding

• math/MathFunctions.h

int power(int base, int exponent);

• math/MathFunctions.cpp

#include <stdio.h>
#include <stdlib.h>
#include "MathFunctions.h"

int power(int base, int exponent) {
    int result = base;
    int i;

    if (exponent == 0) {
        return 1;
    }

    for(i = 1; i < exponent; ++i){
        result = result * base;
    }
    return result;
}

• main.cpp

#include <iostream>
// Add the math directory here
#include "math/MathFunctions.h"

using namespace std;

int main(int argc, char const *argv[]) {
  /* code */
  // cout << "Hello,World!" << power(2, 3) << endl;
  printf("%s power(2,3)=%d \n", "Hello,World!", power(2, 3));
  return 0;
}

• CMakeLists.txt

# CMake Minimum Version Number Requirements
cmake_minimum_required(VERSION 3.15.0)

# Project name
project(hello)

# Find all source files in the current directory and save the name to the SRC_LIST variable
aux_source_directory(. SRC_LIST)
# Find all source files in the math directory and save the name to the MATH_SRC_LIST variable
aux_source_directory(${PROJECT_SOURCE_DIR}/math MATH_SRC_LIST)

# Specify a build target
add_executable(hello ${SRC_LIST} ${MATH_SRC_LIST})

(3) Learn more.

Because there are more math directories, we see that in main.cpp, # include "math/MathFunctions.h" also needs to add directories.

If we don't want to add the math directory, simply # include "MathFunctions.h", as follows:

• main.cpp

#include <iostream>
// Get rid of the math directory here
#include "MathFunctions.h"

using namespace std;

int main(int argc, char const *argv[]) {
  /* code */
  // cout << "Hello,World!" << power(2, 3) << endl;
  printf("%s power(2,3)=%d \n", "Hello,World!", power(2, 3));
  return 0;
}

• CMakeLists.txt Add include_directories

# CMake Minimum Version Number Requirements
cmake_minimum_required(VERSION 3.15.0)

# Project name
project(hello)

# Find all source files in the current directory and save the name to the SRC_LIST variable
aux_source_directory(. SRC_LIST)
# Find all source files in the math directory and save the name to the MATH_SRC_LIST variable
aux_source_directory(${PROJECT_SOURCE_DIR}/math MATH_SRC_LIST)

# Add header file path
include_directories(${PROJECT_SOURCE_DIR}/math)

# Specify a build target
add_executable(hello ${SRC_LIST} ${MATH_SRC_LIST})

Relevant references:
CMake official website
CMake Multiple Source Files - Multiple Directories

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