C3 Language

C3 is a programming language that builds on the syntax and semantics of the C language, with the goal of evolving it while still retaining familiarity for C programmers.

It's an evolution, not a revolution: the C-like for programmers who like C.

Precompiled binaries for the following operating systems are available:

• Windows x64 download, install instructions.
• Linux x64 download, install instructions.
• MacOS Arm64 download, install instructions.
• OpenBSD x64 download, install instructions.

To build the compiler from source instead, see the instructions for building C3 from source.

[Read the C3 Manual]

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Note

Thanks to full ABI compatibility with C, it's possible to mix C and C3 in the same project with no effort. As a demonstration, vkQuake was compiled with a small portion of the code converted to C3 and compiled with the c3c compiler. (The aging fork can be found at https://github.com/c3lang/vkQuake)

A non-curated list of user written projects and other resources can be found here.

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Design Principles

• Procedural "get things done"-type of language.
• Try to stay close to C - only change what's really necessary.
• C ABI compatibility and excellent C integration.
• Learning C3 should be easy for a C programmer.
• Data is inert.
• Avoid "big ideas" & the "more is better" fallacy.
• Introduce some higher level conveniences where the value is great.

C3 owes its inspiration to the C2 language: to iterate on top of C without trying to be a whole new language.

Example code

The following code shows generics (more examples can be found at https://c3-lang.org/language-overview/examples/).

module stack <Type>;
// Above: the parameterized type is applied to the entire module.

struct Stack
{
    usz capacity;
    usz size;
    Type* elems;
}

// The type methods offers dot syntax calls,
// so this function can either be called
// Stack.push(&my_stack, ...) or
// my_stack.push(...)
fn void Stack.push(Stack* this, Type element)
{
    if (this.capacity == this.size)
    {
        this.capacity *= 2;
        if (this.capacity < 16) this.capacity = 16;
        this.elems = realloc(this.elems, Type.sizeof * this.capacity);
    }
    this.elems[this.size++] = element;
}

fn Type Stack.pop(Stack* this)
{
    assert(this.size > 0);
    return this.elems[--this.size];
}

fn bool Stack.empty(Stack* this)
{
    return !this.size;
}

Testing it out:

import stack;

// Define our new types, the first will implicitly create
// a complete copy of the entire Stack module with "Type" set to "int"
alias IntStack = Stack {int};
// The second creates another copy with "Type" set to "double"
alias DoubleStack = Stack {double};

// If we had added "alias IntStack2 = Stack {int}"
// no additional copy would have been made (since we already
// have an parameterization of Stack {int} so it would
// be same as declaring IntStack2 an alias of IntStack

// Importing an external C function is straightforward
// here is an example of importing libc's printf:
extern fn int printf(char* format, ...);

fn void main()
{
    IntStack stack;
    // Note that C3 uses zero initialization by default
    // so the above is equivalent to IntStack stack = {};

    stack.push(1);
    // The above can also be written IntStack.push(&stack, 1);

    stack.push(2);

    // Prints pop: 2
    printf("pop: %d\n", stack.pop());
    // Prints pop: 1
    printf("pop: %d\n", stack.pop());

    DoubleStack dstack;
    dstack.push(2.3);
    dstack.push(3.141);
    dstack.push(1.1235);
    // Prints pop: 1.123500
    printf("pop: %f\n", dstack.pop());
}

In what ways does C3 differ from C?

• No mandatory header files
• New semantic macro system
• Module based name spacing
• Slices
• Operator overloading
• Compile time reflection
• Enhanced compile time execution
• Generics based on generic modules
• "Result"-based zero overhead error handling
• Defer
• Value methods
• Associated enum data
• No preprocessor
• Less undefined behaviour and added runtime checks in "safe" mode
• Limited operator overloading to enable userland dynamic arrays
• Optional pre and post conditions

Current status

The current stable version of the compiler is version 0.7.11.

The upcoming 0.8.0 release will introduce breaking changes, including the removal of deprecated functionality and a major transition from unsigned to signed sizes by default. Follow the issues here.

If you have suggestions on how to improve the language, either file an issue or discuss C3 on its dedicated Discord: https://discord.gg/qN76R87.

The compiler is currently verified to compile on Windows, MacOS, Linux, OpenBSD, NetBSD.

Support matrix

Platform	Native C3 compiler available?	Target supported	Stack trace	Threads	Sockets	Inline asm
Win32 x64	Yes	Yes + cross compilation	Yes	Yes	Yes	Yes*
Win32 Aarch64	Untested	Untested	Untested	Untested	Untested	Yes*
MacOS x64	Yes	Yes + cross compilation	Yes	Yes	Yes	Yes*
MacOS Aarch64	Yes	Yes + cross compilation	Yes	Yes	Yes	Yes*
iOS Aarch64	No	Untested	Untested	Yes	Yes	Yes*
Android Aarch64	No	Untested	Untested	Untested	Untested	Yes*
Android x64	No	Untested	Untested	Untested	Untested	Yes*
Linux x86	Yes	Yes	Yes	Yes	Yes	Yes*
Linux x64	Yes	Yes	Yes	Yes	Yes	Yes*
Linux Aarch64	Yes	Yes	Yes	Yes	Yes	Yes*
Linux Riscv32	Yes	Yes	Yes	Yes	Yes	Untested
Linux Riscv64	Yes	Yes	Yes	Yes	Yes	Untested
ELF freestanding x86	No	Untested	No	No	No	Yes*
ELF freestanding x64	No	Untested	No	No	No	Yes*
ELF freestanding Aarch64	No	Untested	No	No	No	Yes*
ELF freestanding Riscv64	No	Untested	No	No	No	Untested
ELF freestanding Riscv32	No	Untested	No	No	No	Untested
ELF freestanding Xtensa*	No	Untested	No	No	No	Untested
FreeBSD x86	Untested	Untested	No	Yes	Untested	Yes*
FreeBSD x64	Untested	Untested	No	Yes	Untested	Yes*
NetBSD x86	Untested	Untested	No	Yes	Untested	Yes*
NetBSD x64	Untested	Untested	No	Yes	Untested	Yes*
OpenBSD x86	Untested	Untested	No	Yes	Untested	Yes*
OpenBSD x64	Yes*	Yes	Yes*	Yes	Untested	Yes*
MCU x86	No	Untested	No	No	No	Yes*
Wasm32	No	Yes	No	No	No	No
Wasm64	No	Untested	No	No	No	No

* Inline asm is still a work in progress
* OpenBSD 7.8 is the only tested version
* OpenBSD has limited stacktrace, needs to be tested further
* Xtensa support is enabled by compiling with -DXTENSA_ENABLE. The espressif llvm fork is recommended for best compatibility

More platforms will be supported in the future.

What can you help with?

• If you wish to contribute with ideas, please file issues or discuss on Discord.
• Interested in contributing to the stdlib? Please get in touch on Discord.
• Compilation instructions for other Linux and Unix variants are appreciated.
• Would you like to contribute bindings to some library? It would be nice to have support for SDL3 and more. If you have created some bindings, please submit them to https://github.com/c3lang/vendor.
• Build something with C3 and show it off and give feedback. The language is still open for significant tweaks.
• Start work on the C -> C3 converter which takes C code and does a "best effort" to translate it to C3. The first version only needs to work on C headers.
• Do you have some specific area you have deep knowledge of and could help make C3 even better at doing? File or comment on issues.

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Installing

The instructions below install the latest stable release. If you wish to use the bleeding-edge nightly build instead, you can download the latest prerelease binaries here.

Windows

Precompiled binaries

1. Download the zip file: https://github.com/c3lang/c3c/releases/latest/download/c3-windows.zip (debug version here)
2. Unzip exe and standard lib.
3. Run c3c.exe.

Install script

Open a PowerShell terminal (you may need to run it as an administrator) and run the following command:

iwr -useb https://raw.githubusercontent.com/c3lang/c3c/refs/heads/master/install/install.ps1 | iex

The script will inform you once the installation is successful and add the ~/.c3 directory to your PATH, which will allow you to run the c3c command from any location.

You can choose another version with option C3_VERSION. For example, you can force the installation of the 0.7.11 version:

$env:C3_VERSION='0.7.11'; powershell -ExecutionPolicy Bypass -Command "iwr -useb https://raw.githubusercontent.com/c3lang/c3c/refs/heads/master/install/install.ps1 | iex"

(Optional) If you don't have Visual Studio 17 installed, you can run the c3c fetch windows-sdk command which will download the necessary files to compile on Windows.

Scoop

c3c is included in the 'Main' bucket.

scoop install c3

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Linux

Precompiled binaries

1. Download tar file: https://github.com/c3lang/c3c/releases/latest/download/c3-linux-static.tar.gz (debug version here)
2. Unpack executable and standard lib.
3. Run ./c3c.

Install script

Open a terminal and run the following command:

curl -fsSL https://raw.githubusercontent.com/c3lang/c3c/refs/heads/master/install/install.sh | bash

The C3 compiler will be installed, and the script will also update your ~/.bashrc to include ~/.c3 in your PATH, allowing you to invoke the c3c command from anywhere. You might need to restart your terminal or source your shell for the changes to take effect.

You can choose another version with option C3_VERSION. For example, you can force the installation of the 0.7.11 version:

curl -fsSL https://raw.githubusercontent.com/c3lang/c3c/refs/heads/master/install/install.sh | C3_VERSION=0.7.11 bash

Arch Linux

Arch includes c3c in the official 'extra' repo. It can be easily installed the usual way:

sudo pacman -S c3c
# or paru -S c3c
# or yay -S c3c
# or aura -A c3c

There is also an AUR package for the c3c compiler : c3c-git.

You can use your AUR package manager:

paru -S c3c-git
# or yay -S c3c-git
# or aura -A c3c-git

Or clone it manually:

git clone https://aur.archlinux.org/c3c-git.git
cd c3c-git
makepkg -si

Fedora

C3 is available as a community maintained COPR package for Fedora.
To install via dnf:

sudo dnf copr enable sisyphus1813/c3
sudo dnf install c3

NixOS / Nix

You can access c3c via flake.nix, which will contain the latest commit of the compiler. To add c3c to your flake.nix, do the following:

flake.nix example

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs?ref=nixpkgs-unstable";
    flake-utils.url = "github:numtide/flake-utils";
    c3c.url = "github:c3lang/c3c";
    # Those are desired if you don't want to copy extra nixpkgs
    c3c.inputs = {
      nixpkgs.follows = "nixpkgs";
      flake-utils.follows = "flake-utils";
    };
  };

  outputs = { self, ... } @ inputs: inputs.flake-utils.lib.eachDefaultSystem (system:
    let
      pkgs = import inputs.nixpkgs { inherit system; };
      c3c = inputs.c3c.packages.${system}.c3c;
    in
    {
      devShells.default = pkgs.mkShell {
        buildInputs = [
          pkgs.c3c
        ];
      };
    }
  );
}

Gentoo

c3c is available in the Gentoo GURU overlay.

Enable and sync the GURU repository (if not already done):

sudo eselect repository enable guru
sudo emaint sync -r guru

Install c3c with:

sudo emerge -av dev-lang/c3c

• The compiler binary is installed to /usr/bin/c3c.
• The standard library is installed to /usr/lib/c3.

For Gentoo-specific issues, please use the Gentoo Bugzilla (Product: GURU).

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MacOS

Precompiled binaries

1. Make sure you have XCode with command line tools installed.
2. Download the zip file: https://github.com/c3lang/c3c/releases/latest/download/c3-macos.zip (debug version here)
3. Unzip executable and standard lib.
4. Run ./c3c.

(*Note that there is a known issue with debug symbol generation on MacOS 13, see issue #1086)

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OpenBSD

Precompiled binaries

1. Download tar file: https://github.com/c3lang/c3c/releases/latest/download/c3-openbsd.tar.gz (debug version here)
2. Unpack executable and standard lib.
3. Run ./c3c.

(*Note that this is specifically for OpenBSD 7.8, running it on any other version is prone to ABI breaks)

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Docker

You can build c3c using an Ubuntu container. By default, the script will build through Ubuntu 22.04. You can specify the version by passing the UBUNTU_VERSION environment variable.

UBUNTU_VERSION=20.04 ./build-with-docker.sh

See the build-with-docker.sh script for more information on other configurable environment variables.

Getting started with a "hello world"

Create a main.c3 file with:

module hello_world;
import std::io;

fn void main()
{
   io::printn("Hello, world!");
}

Make sure you have the standard libraries at either ../lib/std/ or /lib/std/.

Then run

c3c compile main.c3

The generated binary will by default be named after the module that contains the main function. In our case that is hello_world, so the resulting binary will be called hello_world or hello_world.exedepending on platform.

Building C3 from Source

Compiling on MacOS

1. Install Homebrew
2. Install CMake: brew install cmake
3. Clone the C3C github repository: git clone https://github.com/c3lang/c3c.git
4. Enter the C3C directory cd c3c.
5. Set up CMake build: cmake -B build -S . -DC3_FETCH_LLVM=ON
6. Build: cmake --build build
7. Change directory to the build directory cd build

Compiling on Windows

1. Make sure you have Visual Studio 17 2022 installed or alternatively install the "Buildtools for Visual Studio" (https://aka.ms/vs/17/release/vs_BuildTools.exe) and then select "Desktop development with C++"
2. Install CMake
3. Clone the C3C github repository: git clone https://github.com/c3lang/c3c.git
4. Enter the C3C directory: cd c3c.
5. Set up the CMake build: cmake --preset windows-vs-2022-release
6. Build: cmake --build --preset windows-vs-2022-release

You should now have a c3c executable in build\Release.

You can try it out by running some sample code: c3c.exe compile ../../resources/examples/hash.c3

Building c3c using Visual Studio Code is also supported when using the CMake Tools extension. Simply select the Windows x64 Visual Studio 17 2022 configure preset and build.

Note that if you run into linking issues when building, make sure that you are using the latest version of VS17.

Note

Debug Build: To avoid LLVM library conflicts, configure and build using the debug preset instead:

cmake --preset windows-vs-2022-debug
cmake --build --preset windows-vs-2022-debug

(Your executable will be located in build-debug\Debug)

Compiling on Linux

1. Install required build dependencies using your distribution's package manager:

   • Ubuntu / Debian: sudo apt-get install cmake git clang libcurl4-openssl-dev
   • Fedora: sudo dnf install cmake clang git libcurl-devel
   • Arch Linux: sudo pacman -S curl clang cmake git
   • Void Linux: sudo xbps-install git cmake clang libcurl-devel
   • Other distributions: Install CMake, Git, a C compiler (like Clang), and libcurl development headers.

2. Clone the C3C repository and enter the directory:

   git clone https://github.com/c3lang/c3c.git
   cd c3c

   (If you only need the latest commit, add --depth=1 to the clone command)

3. Create the CMake build cache:

   cmake -B build -S . -DC3_FETCH_LLVM=ON -DCMAKE_BUILD_TYPE=Release

4. Build the compiler:

   cmake --build build

5. You should now have a c3c executable in the build directory. You can test it by compiling an example:

   ./build/c3c compile resources/examples/hash.c3

   (Optional) To install the compiler globally: sudo cmake --install build

Compiling on NixOS

1. Enter nix shell, by typing nix develop in root directory
2. Configure cmake via cmake . -Bbuild $=C3_CMAKE_FLAGS. Note: passing C3_CMAKE_FLAGS is needed to generate compile_commands.json and find missing libs.
3. Build it cmake --build build
4. Test it out: ./build/c3c -V
5. If you use clangd lsp server for your editor, it is recommended to make a symbolic link to compile_command.json in the root: ln -s ./build/compile_commands.json compile_commands.json

A note on compiling for Linux/Unix/MacOS: to be able to fetch vendor libraries libcurl is needed. The CMake script should detect it if it is available. Note that this functionality is non-essential and it is perfectly fine to use the compiler without it.

Licensing

Unless specified otherwise, the code in this repository is MIT licensed. The exception is the compiler source code (the source code under src), which is licensed under LGPL 3.0.

This means you are free to use all parts of standard library, tests, benchmarks, grammar, examples and so on under the MIT license, including using those libraries and tests if you build your own C3 compiler.

Editor plugins

Editor plugins can be found at https://github.com/c3lang/editor-plugins.

Contributing unit tests

1. Write the test, either adding to existing test files in /test/unit/ or add a new file. (If testing the standard library, put it in the /test/unit/stdlib/ subdirectory).
2. Make sure that the test functions have the @test attribute.
3. Run tests and see that they pass. (Recommended settings: c3c compile-test -O0 test/unit.
   • in this example test/unit/ is the relative path to the test directory, so adjust as required)
4. Make a pull request for the new tests.

Thank yous

A huge THANK YOU goes out to all contributors and sponsors.

A special thank you to sponsors Zack Puhl and konimarti for going the extra mile.

And honorable mention goes to past sponsors: Ygor Pontelo, Simone Raimondi, Jan Válek, Pierre Curto, Caleb-o and devdad

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