Project setup#

Resulting code: step000

In our running example, we use CMake to organize the compilation of the code. This is a very standard way of handling cross-platform builds, and we follow the idioms of modern cmake.

Requirements#

All we need is CMake and a C++ compiler, instructions are detailed below per OS.

Hint

After the installation, you can type which cmake (linux/macOS) or where cmake (Windows) to see whether your command line finds the full path to the cmake command. If not, make sure your PATH environment variable contains the directory where CMake is installed.

Linux#

If you are under an Ubuntu/Debian distribution, install the following packages:

sudo apt install cmake build-essential

Other distributions have equivalent packages, make sure you have the commands cmake, make and g++ working.

Windows#

Download and install CMake from the download page. You may use either Visual Studio or MinGW as a compiler toolkit.

MacOS#

You can install CMake using brew install cmake, and XCode to build the project.

Minimal project#

The most minimal project consists then in a main.cpp source file, and a CMakeLists.txt build file.

Let us start with the classic hello world in main.cpp:

#include <iostream>

int main (int, char**) {
    std::cout << "Hello, world!" << std::endl;
    return 0;
}

In CMakeLists.txt, we specify that we want to create a target of type executable, called “App” (this will also be the name of the executable file), and whose source code is main.cpp:

add_executable(App main.cpp)

CMake also expects at the beginning of CMakeLists.txt to know the version of CMake the file is written for (minimum supported…your version) and some information about the project:

cmake_minimum_required(VERSION 3.0...3.25)
project(
    LearnWebGPU # name of the project, which will also be the name of the visual studio solution if you use it
    VERSION 0.1.0 # any version number
    LANGUAGES CXX C # programming languages used by the project
)
{{Define app target}}
{{Recommended extras}}

Building#

We are now ready to build our minimal project. Open a terminal and go to the directory where you have the CMakeLists.txt and main.cpp files:

cd your/project/directory

Hint

From a Windows explorer window showing your project’s directory, press Ctrl+L, then type cmd and hit return. This opens a terminal in the current directory.

Let us now ask CMake to create the build files for our project. We ask it to isolate the build files from our source code by placing them in a build/ directory with the -B build option. This is very much recommended, in order to be able to easily distinguish these generated files from the ones we manually wrote (a.k.a. the source files):

cmake . -B build

This creates the build files for either make, Visual Studio or XCode depending on your system (you can use the -G options to force a particular build system, see cmake -h for more info). To finally build the program and generate the App (or App.exe) executable, you can either open the generated Visual Studio or XCode solution, or type in the terminal:

cmake --build build

Then run the resulting program:

build/App  # linux/macOS
build\Debug\App.exe  # Windows

Recommended extras#

We set up some properties of the target App by calling somewhere after add_executable the set_target_properties command.

set_target_properties(App PROPERTIES
    CXX_STANDARD 17
    CXX_EXTENSIONS OFF
    COMPILE_WARNING_AS_ERROR ON
)

The CXX_STANDARD property is set to 17 to mean that we require C++17 (this will enable us to use some syntactic tricks later on, but is not mandatory per se).

The CXX_EXTENSIONS property is set to OFF to disable compiler specific extensions (for example, on GCC this will make CMake add “-std=c++17” and not “-std=gnu++17” to the list of compilation flags).

The COMPILE_WARNING_AS_ERROR is turned on as a good practice, to make sure no warning is left ignored. Warnings are actually important, especially when learning a new language/library. To make sure we even have as many warnings as possible, we add some compile options:

if (MSVC)
    target_compile_options(App PRIVATE /W4)
else()
    target_compile_options(App PRIVATE -Wall -Wextra -pedantic)
endif()

Note

In the accompanying code, I hid these details in the target_treat_all_warnings_as_errors() function defined in utils.cmake and included at the beginning of the CMakeLists.txt.

On MacOS, CMake can generate XCode project files. However, by default, no schemes are created, and XCode itself generates a scheme for each CMake target – usually we only want a scheme for our main target. Therefore, we set the XCODE_GENERATE_SCHEME property. We will also already enable frame capture for GPU debugging.

if(XCODE)
    set_target_properties(App PROPERTIES
        XCODE_GENERATE_SCHEME ON
        XCODE_SCHEME_ENABLE_GPU_FRAME_CAPTURE_MODE "Metal")
endif()

We now have a good basic project configuration, that we’ll build upon in the next chapters. We are ready to move on to opening a window.

Resulting code: step000