Compiler Explorer

Compiler Explorer is an interactive compiler. The left-hand pane shows editable C, C++, Rust, Go, D, Haskell, Swift, Pascal (and some more!) code. The right, the assembly output of having compiled the code with a given compiler and settings. Multiple compilers are supported, and the UI layout is configurable (thanks to GoldenLayout). There is also an ispc compiler ? for a C variant with extensions for SPMD.

Try out at godbolt.org.

You can support this project on Patreon.

Compiler Explorer follows a Code of Conduct which aims to foster an open and welcoming environment.

Compiler Explorer was started in 2012 to serve my needs at my previous employer to show how C++ constructs translated to assembly code. It started out as a tmux session with vi running in one pane and watch gcc -S foo.cc -o - running in the other.

Since then, it has become a public website serving around 2,000,000 compilations per week.

Using Compiler Explorer

FAQ

There is now a FAQ section in the repository wiki. If your question is not present, please contact us as described below so we can help you. If you find that the FAQ is lacking some important point, please free to contribute to it and/or ask us to clarify it.

Videos

There are a number of videos that showcase some of the features of Compiler Explorer:

• presentation for CppCon 2019 about the project
• older 2 part series of videos which go into a bit more detail into the more obscure features.
• playlist: Compiler Explorer: A collection of videos discussing Compiler Explorer; using it, installing it, what it's for, etc.

Developing

Compiler Explorer is written in Node.js.

Assuming you have a compatible version of node installed, simply running make ought to get you up and running with an Explorer running on port 10240 on your local machine: http://localhost:10240/. Currently Compiler Explorer requires the latest LTS node version (v12) installed, either on the path or at NODE_DIR (an environment variable or make parameter).

Running with make EXTRA_ARGS='--language LANG' will allow you to load LANG exclusively, where LANG is one for the language ids/aliases defined in lib/languages.js. The Makefile will automatically install all the third party libraries needed to run; using npm to install server-side and client side components.

For development, we suggest using make dev to enable some useful features, such as automatic reloading on file changes and shorter startup times.

You can also use npm run dev to run if make dev doesn't work on your machine.

Some languages need extra tools to demangle them, e.g. rust, d, or haskell. Such tools are kept separately in the tools repo.

The config system leaves a lot to be desired. This is something we want to improve.

A Road map is available which gives a little insight into the future plans for Compiler Explorer.

Running a local instance

If you want to point it at your own GCC or similar binaries, either edit the etc/config/LANG.defaults.properties or else make a new one with the name LANG.local.properties, substituting LANG as needed. *.local.properties files have the highest priority when loading properties.

When running in a corporate setting the URL shortening service can be replaced by an internal one if the default storage driver isn't appropriate for your environment. To do this, add a new module in lib/shortener/myservice.js and set the urlShortenService variable in configuration. This module should export a single function, see the tinyurl module for an example.

RESTful API

There's a simple restful API that can be used to do compiles to asm and to list compilers.

You can find the API documentation here.

Contact us

We run a Compiler Explorer Discord, which is a place to discuss using or developing Compiler Explorer. We also have a presence on the cpplang slack channel #compiler_explorer and we have a public mailing list.

There's a development channel on the discord, and also a development mailing list.

Feel free to raise an issue on github or email Matt directly for more help.

Credits

Compiler Explorer is maintained by the awesome people listed in the AUTHORS file.

We would like to thank the contributors listed in the CONTRIBUTORS file, who have helped shape Compiler Explorer.

We would also like to specially thank these people for their contributions to Compiler Explorer:

• Gabriel Devillers (while working for Kalray)
• Johan Engelen
• Joshua Sheard
• Marc Poulhiès
• Andrew Pardoe

A number of amazing sponsors, both individuals and companies, have helped fund and promote Compiler Explorer. We would also like to thank JetBrains for their support and for donating licenses to their excellent products to develop Compiler Explorer.