Lab 2 - C++, CMake & IDE

Responsible: Ing. Adam Ligocki, Ph.D.

If you are not familiar with Linux CLI commands, please follow the Linux chapter.

CLI Compilation (30 min)

This exercise will show you how to write and compile the most basic c++ project in Linux OS.

In your home directory create a project folder and enter it.

Write a simple program into the main.cpp file.

#include <iostream>

#define A 5

int sum(int a, int b) {
    return a + b;
}

int main() {
    std::cout << "My Cool CLI Compiled Program" << std::endl;
    int b = 10;
    std::cout << "Sum result: " << sum(A, b) << std::endl;
    return 0;
}

Save file and compile it using the gcc call (GCC a C/C++ compiler). 

g++ -o my_cool_program main.cpp

And run binary

./my_cool_program

There are other alternatives, like CLang, LLVM, and many others

Challenge 1

  • In your project folder, create and include folder
  • in the include folder create and lib.hpp file and write some function into it
  • use the function from lib.hpp in the main.cpp
  • compile and run program (tip: use -I <folder> argument for gcc to specify folder with header files)

Challenge 2

  • in the projet folder create the lib.cpp

  • move the function implementation from lib.hpp to lib.cpp; keep function declaration in lib.hpp

  • compile and run program (tip: you have to compile both main.cpp and lib.cpp)

  • helper: gcc -o <output_binary> <source_1.cpp source_2.cpp ...> -I <folder_with_headers>

  • Discuss the difference between preprocessing code, compiling code and linking objects.

  • Delete project folder

CMake Project (30 min)

Before reading following text, please get familiar with CMake.

Now let's create a similar project, but using CMake.

  • Determine your current location in the file system.
  • Switch to your home directory.
  • Create a new project folder.
  • Inside this folder, create several subdirectories so that the structure looks like this (use the tree command to verify):
/MyProject
 |--build
 |--include
 | \--MyProject
 \--src
  • Using any text editor (like nano or vim) to create the following files: main.cpp, lib.cpp, lib.hpp, and CMakeLists.txt in your home directory.
  • Move (do not copy) the main.cpp adn lib.cpp files into the src subdirectory.
  • Move the lib.hpp file into the include/MyProject subdirectory.
  • Move the CMakeLists.txt file into the root of the project folder.

Now your project should look like this:

/MyProject
 |--build
 |--CMakeLists.txt
 |--include
 | \--MyProject
 |   \--lib.hpp
 \--src
   |--lib.cpp
   \--main.cpp
  • Using text editor fill the main.cpp, lib.cpp and lib.hpp files with required code.
  • Using the text editor fill the CMakeLists.txt
cmake_minimum_required(VERSION 3.10)
project(MyProject)
set(CMAKE_CXX_STANDARD 17)
include_directories(include/)
add_executable(my_program src/main.cpp src/lib.cpp)

Now try co compile project. In the project folder follows:

cd my_project_dir  # go to your project directoyr
mkdir build  # create build folder
cd build   # enter the build folder
cmake ..   # call cmake and search for CMakeLists.txt in the folder above
make    # build program
./<binary_name>   # run program

Optional: try to compile program manualy.

g++ <source1 source2 source3 ...> -I <include_directory> -o <output_binary>
  • Delete project folder

CLion IDE (30 min)

Create a same project using the CLion IDE.

To learn how to control CLion, please take a look on tutorial or official doc.

Unit Tests, GTest (30 min)

The unit tests are an effective way of developing software. It is called test-oriented-development. First we define the required functionality, than we write a tests that covers requirements and finally we implement the algorithms. When the tests are passing, it means we fulfilled requirements.

In the same time, if we work on large scale projects where many people cooperates and many changes are done, the unit tests allows us to trace the potential bugs that might be introduced with changes. It is called Continuous Integration (CI).

There are many frameworks that helps implement testing. In this course we are going to use the GTest by Google as it is one of the most common tool in this field.

GTest Installation

If there is no GTest installed on the system follow these instructions.

# install necessary packages 
sudo apt update
sudo apt install cmake build-essential libgtest-dev

# compile gtest
cd /usr/src/gtest
sudo cmake .
sudo make

# install libs into system
sudo cp lib/*.a /usr/lib

Take a look if the libraries are in the system

ls /usr/lib | grep gtest

# you shoul see:
# libgtest.a
# libgtest_main.a

Adding Unit Test to Project

In your project directory add the test folder.

/MyProject
 |--include
 |--src
 \--test

Add the add_subdirectory(test) line at the end of CMakeLists.txt file.

Create CMakeLists.txt file in the test folder.

cmake_minimum_required(VERSION 3.10)

find_package(GTest REQUIRED)
enable_testing()

add_executable(my_test my_test.cpp)
target_link_libraries(my_test GTest::GTest GTest::Main)
gtest_discover_tests(my_test)

Create my_test.cpp file.

#include <gtest/gtest.h>

float add(float a, float b) {
    return a + b;
}

TEST(test, test_should_pass) {
    EXPECT_EQ(add(5.0f, 10.0), 15.0);
    EXPECT_NE(add(5.0f, 10.0), 0.0);
}

TEST(test, test_should_fail) {
    EXPECT_EQ(add(10.0f, 10.0), 20.0);
}

int main(int argc, char** argv) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

In the bottom of the CLion open console and run

mkdir build && cd build
cmake ..
make
cd test
ctest

You should see the test evaluation.

You can also evaluate tests in directly in the CLion by reloading the CMake and the test will be available as an executable on the top of the window.

CLion Ctest

C++ Trainig (2h)

Take a look on basic c++ tutorial and more advanced multithreading tutorial.