This document explains how to add a new library to Compiler Explorer (“CE” from here on), first for a local instance, and then how to submit PRs to get it into the main CE site.
Library configurations are part of the compiler's properties, which is done through the etc/config/c++.*.properties files (for C++, other languages follow the obvious pattern). The various named configuration files are used in different contexts: for example etc/config/c++.local.properties take priority over etc/config/c++.defaults.properties. The local version is ignored by git, so you can make your own personalised changes there. The live site uses the etc/config/c++.amazon.properties file.
Within the file, configuration is a set of key and value pairs, separated by an =. Whitespace is not trimmed. Lines starting with # are considered comments and not parsed. The list of libraries is set by the libs key and is a list of library identifiers, separated by colons. The identifier itself is not important, but must be unique to that library.
An example configuration:
libs=kvasir:boost:rangesv3
This says there are three libraries with identifiers kvasir, boost and rangesv3. CE will look for the key named libs.ID.versions, libs.ID.name and the optionals libs.ID.url & libs.ID.description. The ID is the identifier (The one we just set) of the library being looked up. The name key expects the human readable name of the library (Note that you can use spaces here!) The versions key expects another list, akin to the libs key itself. This time, you have to define the available versions for each library. The url key expects an unescaped url, where users can go to learn more about the library (This is usually the project‘s homepage, or in its absence, the GitHub repo) The description key should be use as an extremely short description of the library. Usually used to spell the library’s full name in cases where the name key is an acronym.
For example:
libs.kvasir.name=Kvasir::mpl libs.kvasir.versions=trunk libs.kvasir.url=https://github.com/kvasir-io/Kvasir libs.boost.name=Boost libs.boost.versions=164:165 libs.boost.url=http://www.boost.org/ libs.rangesv3.name=range-v3 libs.rangesv3.description=Range library for C++11/14/17 libs.rangesv3.versions=trunk:030 libs.rangesv3.url=https://github.com/ericniebler/range-v3
Now, for each declared version, CE will look for a version key, an human readable string representing the corresponding version, and path, a list consisting of the paths to add to the inclusion path of the library.
This would leave us with: (Empty lines added for clarity. Please refrain from using them if you plan to PR us :D)
libs.kvasir.name=Kvasir::mpl libs.kvasir.versions=trunk libs.kvasir.url=https://github.com/kvasir-io/Kvasir libs.kvasir.versions.trunk.version=trunk # Note how there are 2 paths defined for Kvasir in our case (Example usage!) libs.kvasir.versions.trunk.path=/opt/compiler-explorer/libs/kvasir/mpl/trunk/src/kvasir:/opt/compiler-explorer/libs/kvasir/mpl/trunk/src libs.boost.name=Boost libs.boost.versions=164:165 libs.boost.url=http://www.boost.org/ libs.boost.versions.164.version=1.64 libs.boost.versions.165.version=1.65 libs.boost.versions.164.path=/opt/compiler-explorer/libs/boost_1_64_0 libs.boost.versions.165.path=/opt/compiler-explorer/libs/boost_1_65_0 libs.rangesv3.name=range-v3 libs.rangesv3.versions=trunk:030 libs.rangesv3.url=https://github.com/ericniebler/range-v3 libs.rangesv3.versions.trunk.version=trunk libs.rangesv3.versions.030.version=0.3.0 libs.rangesv3.versions.trunk.path=/opt/compiler-explorer/libs/rangesv3/trunk/include libs.rangesv3.versions.030.path=/opt/compiler-explorer/libs/rangesv3/0.3.0/include
The defaultLibs key specifies an array of libs/versions which will be enabled by default when the user visits the site. The expected format is:
defaultLibs=libKeyA.version:libKeyB.version:libKeyC.version
Where libKey is the key of the library to be enabled by default, and version is the version key to load. Note that the site won't complain if invalid key/version pairs are set. Repeating a lib key more than once is supported.
It should be pretty straightforward to add a library of your own. Create a etc/config/c++.local.properties file and override the libs list to include your own library, and its configuration.
Once you've done that, running make should pick up the configuration and you should be able to use them from the library dropdown on the compiler view (The book icon)
If you're looking to add libraries for another language, obviously create the etc/config/LANG.local.properties in the above steps, and run with make EXTRA_ARGS='--language LANG (e.g. etc/config/rust.local.properties and make EXTRA_ARGS='--language Rust').
Test locally, and for many compilers that‘s probably all you need to do. Some compilers might need a few options tweaks (like the intel asm setting, or the version flag). For a completely new compiler, you might need to define a whole new compilerType. Doing so is beyond this document’s scope at present, but take a look inside lib/compilers/ to get some idea what might need to be done.
On the main CE website, libraries are installed into a /opt/compiler-explorer/ directory by a set of scripts in the sister GitHub repo: https://github.com/mattgodbolt/compiler-explorer-image
In the update_compilers directory in that repository are a set of scripts that download and install the libraries. If you wish to test locally, and can create a /opt/compiler-explorer directory on your machine which is readable and writable by your current user, then you can run the scripts directly.
If your library fits nicely into the harness then it should be straightforward to add it there. Anything more complex: contact the CE authors for more help.
Remember to also add the library dependencies following the same steps. It's on you if those should also appear in the UI.
Hopefully that‘s enough to get an idea. The ideal case should be a pull request to add a couple of lines to the compiler-explorer-image to install the library, and a pull request to add a few lines to the LANG.amazon.properties file in this repository. Once that’s done, remember to update the wiki with the new library, adding the library in alphabetical order, with newer versions on top.
If you feel like we could improve this document in any way, please contact us. We'd love to hear from you!