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.
• Debian x64 download, install instructions.
• Ubuntu x86 download, install instructions.
• MacOS Arm64 download, install instructions.

The manual for C3 can be found at www.c3-lang.org.

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 fork can be found at https://github.com/c3lang/vkQuake)

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 generic modules (more examples can be found at https://c3-lang.org/references/docs/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"
def IntStack = Stack(<int>);
// The second creates another copy with "Type" set to "double"
def DoubleStack = Stack(<double>);

// If we had added "define 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
• 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 0.6.4.

The upcoming 0.6.x releases will focus on expanding the standard library. 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 Linux, Windows and MacOS.

Support matrix

* Inline asm is still a work in progress

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 SDL, Raylib and more.
• 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.

Installing

Installing on Windows with precompiled binaries

1. Download the zip file: https://github.com/c3lang/c3c/releases/download/latest/c3-windows.zip (debug version here)
2. Unzip exe and standard lib.
3. If you don't have Visual Studio 17 installed you can either do so, or run the msvc_build_libraries.py Python script which will download the necessary files to compile on Windows.
4. Run c3c.exe.

Installing on Debian with precompiled binaries

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

Installing on Ubuntu with precompiled binaries

1. Download tar file: https://github.com/c3lang/c3c/releases/download/latest/c3-ubuntu-20.tar.gz (debug version here)
2. Unpack executable and standard lib.
3. Run ./c3c.

Installing on MacOS with precompiled binaries

1. Make sure you have XCode with command line tools installed.
2. Download the zip file: https://github.com/c3lang/c3c/releases/download/latest/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)

Installing on 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

Building via Docker

You can build c3c using either an Ubuntu 18.04 or 20.04 container:

./build-with-docker.sh 18

Replace 18 with 20 to build through Ubuntu 20.04.

For a release build specify:

./build-with-docker.sh 20 Release

A c3c executable will be found under bin/.

Installing on OS X using Homebrew

2. Install CMake: brew install cmake
3. Install LLVM 17+: brew install llvm
4. Clone the C3C github repository: git clone https://github.com/c3lang/c3c.git
5. Enter the C3C directory cd c3c.
6. Create a build directory mkdir build
7. Change directory to the build directory cd build
8. Set up CMake build for debug: cmake ..
9. Build: cmake --build .

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.

Compiling

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 -B build -G "Visual Studio 17 2022" -A x64 -DCMAKE_BUILD_TYPE=Release
6. Build: cmake --build build --config Release
7. You should now have the c3c.exe

You should now have a c3c executable.

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

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

Compiling on Ubuntu 24.04 LTS

1. Make sure you have a C compiler that handles C11 and a C++ compiler, such as GCC or Clang. Git also needs to be installed.
2. Install LLVM 18 sudo apt-get install cmake git clang zlib1g zlib1g-dev libllvm18 llvm llvm-dev llvm-runtime liblld-dev liblld-18 libpolly-18-dev
3. Clone the C3C github repository: git clone https://github.com/c3lang/c3c.git
4. Enter the C3C directory cd c3c.
5. Create a build directory mkdir build
6. Change directory to the build directory cd build
7. Set up CMake build: cmake ..
8. Build: cmake --build .

You should now have a c3c executable.

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

Compiling on Void Linux

1. As root, ensure that all project dependencies are installed: xbps-install git cmake llvm17 llvm17-devel lld17-devel libcurl-devel ncurses-devel zlib-devel libzstd-devel libxml2-devel
2. Clone the C3C repository: git clone https://github.com/c3lang/c3c.git
   • If you only need the latest commit, you may want to make a shallow clone instead: git clone https://github.com/c3lang/c3c.git --depth=1
3. Enter the directory: cd c3c
4. Create a build directory: mkdir build
5. Enter the build directory: cd build
6. Create the CMake build cache: cmake ..
7. Build: cmake --build .

Your c3c executable should have compiled properly. You may want to test it: ./c3c compile ../resources/examples/hash.c3
For a sytem-wide installation, run the following as root: cmake --install .

Compiling on other Linux / Unix variants

1. Install CMake.
2. Install or compile LLVM and LLD libraries (version 17+ or higher)
3. Clone the C3C github repository: git clone https://github.com/c3lang/c3c.git
4. Enter the C3C directory cd c3c.
5. Create a build directory mkdir build
6. Change directory to the build directory cd build
7. Set up CMake build for debug: cmake ... At this point you may need to manually provide the link path to the LLVM CMake directories, e.g. cmake -DLLVM_DIR=/usr/local/opt/llvm/lib/cmake/llvm/ ..
8. Build: cmake --build .

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 user the compiler without it.

Licensing

The C3 compiler is licensed under LGPL 3.0, the standard library itself is MIT licensed.

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 Caleb-o and devdad for going the extra mile.