Indexing a C++ repository with LSIF
This guide walks through setting up LSIF generation for a C++ codebase using Docker and
lsif-clang. These instructions should apply to any
C++ project that is buildable with
clang++ (which also covers most projects built
Note on Docker: LSIF generation requires a working build environment (the LSIF indexer essentially takes the place of the compiler), and Docker allows us to recreate this environment consistently. If you prefer not to use Docker, you can easily adapt these instructions to a non-Docker-based system simply by converting all the steps in the Dockerfile to a script or steps in your CI configuration.
We will be using github.com/sourcegraph/tesseract as an example C++ repository.
Copy the files in the
lsif-dockerdirectory of sourcegraph/tesseract to a local
lsif-dockerdirectory. We recommend adding this directory to the repository being indexed.
Replace the contents of
lsif-docker/install_build_deps.shwith commands that install any requisite build dependencies of the project. These should be dependencies that do not vary from revision to revision.
lsif-docker/checkout.shto clone your repository to the
/sourcedirectory in the Docker container’s filesystem.
lsif-docker/gen_compile_commands.shto generate a compilation database (
If you use autotools to build your project (
./autogen.sh && ./configure && make), you can probably keep the existing contents.
If you build your project using CMake, you can use
cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ..
If you use Bazel, you can use bazel-compilation-database:
git clone --depth=10 https://github.com/grailbio/bazel-compilation-database.git /bazel-compilation-database /bazel-compilation-database/generate.sh
If you use another build system or if any of the above steps break, consult this very helpful guide to generating compilation databases for various build systems. It may be helpful to
docker buildyour container and
docker run -it $IMAGEto get an interactive shell into the container, so you can ensure the build environment is correct. We recommend getting the project to build normally first (e.g., emit a binary) and then following the aforementioned guide to modify the regular build steps to emit a compilation database.
- Most often, the
compile_commands.jsonfile will be emitted in the root directory of the repository. If this is not the case, you’ll also need to modify
cdinto the directory containing it and then run
lsif-clang --project-root=/source compile_commands.json. If you’re unsure of where
compile_commands.jsonwill be emitted, just continue to the next step for now.
- Most often, the
docker build lsif-dockerto build the Docker image.
Generate a Sourcegraph access token from your Sourcegraph instance (Settings > Access tokens). Give it
Run the following command to generate and upload LSIF data to Sourcegraph:
docker run -e SRC_ACCESS_TOKEN=$ACCESS_TOKEN -e SRC_ENDPOINT=https://sourcegraph.example.com -e PROJECT_REV=HEAD $IMAGE_ID
with the following substitutions:
SRC_ACCESS_TOKEN=: the Sourcegraph access token you just created
SRC_ENDPOINT=: the URL to your Sourcegraph instance
PROJECT_REV=: the revision of you repository to be indexed
$IMAGE_ID: the ID of the Docker image you just built
Finally, you can incorporate the Dockerized LSIF generation into your CI pipeline so it runs on every new revision on any appropriate branch.
docker run command fails, you likely have an error in one of the
files. The general rule is if you can get your project to build normally (i.e., generate an
executable), you can get the LSIF indexer to generate LSIF. So we recommend the following approach
if things don’t work on the first try:
- Build the Docker image:
docker build lsif-docker
- Run the container with an interactive shell:
docker run -it $IMAGE_ID bash
- In the container shell,
cd /sourceand figure out what steps are needed to build the project.
- Once the build successfully completes, figure out which steps are needed to generate the
compile_commands.jsonfile. We have found this guide to be a useful resource.
- Once you’ve successfully generated
cdinto the directory containing
lsif-clang --project-root=/source compile_commands.json. This should generate a
dump.lsiffile in the same directory. This
dump.lsifshould contain JSON describing all the symbols and references in the codebase (it should be rather large).
- Once the
dump.lsiffile is generated correctly, set the environment variables
SRC_ENDPOINTto the appropriate values in your shell. Then run
src lsif uploadfrom the directory containing the
lsif.dumpfile. This should successfully upload the LSIF dump to Sourcegraph.
- After you’ve successfully done all of the above in the container’s interactive shell, incorporate
these steps into the
lsif-docker/*.shfiles. Then re-build the Docker container and try running