How To Validate a New Release


This document contains information about testing the release candidates that will ultimately be the next LLVM release. For more information on how to manage the actual release, please refer to How To Release LLVM To The Public.

Overview of the Release Process

Once the release process starts, the Release Manager will ask for volunteers, and it’ll be the role of each volunteer to:

  • Test and benchmark the previous release

  • Test and benchmark each release candidate, comparing to the previous release and candidates

  • Identify, reduce and report every regression found during tests and benchmarks

  • Make sure the critical bugs get fixed and merged to the next release candidate

Not all bugs or regressions are show-stoppers and it’s a bit of a grey area what should be fixed before the next candidate and what can wait until the next release.

It’ll depend on:

  • The severity of the bug, how many people it affects and if it’s a regression or a known bug. Known bugs are “unsupported features” and some bugs can be disabled if they have been implemented recently.

  • The stage in the release. Less critical bugs should be considered to be fixed between RC1 and RC2, but not so much at the end of it.

  • If it’s a correctness or a performance regression. Performance regression tends to be taken more lightly than correctness.


The scripts are in the utils/release directory.

This script will check-out, configure and compile LLVM+Clang (+ most add-ons, like compiler-rt, libcxx, libomp and clang-extra-tools) in three stages, and will test the final stage. It’ll have installed the final binaries on the Phase3/Releasei(+Asserts) directory, and that’s the one you should use for the test-suite and other external tests.

To run the script on a specific release candidate run:

./ \
     -release 3.3 \
     -rc 1 \
     -no-64bit \
     -test-asserts \

Each system will require different options. For instance, x86_64 will obviously not need -no-64bit while 32-bit systems will, or the script will fail.

The important flags to get right are:

  • On the pre-release, you should change -rc 1 to -final. On RC2, change it to -rc 2 and so on.

  • On non-release testing, you can use -final in conjunction with -no-checkout, but you’ll have to create the final directory by hand and link the correct source dir to final/llvm.src.

  • For release candidates, you need -test-asserts, or it won’t create a “Release+Asserts” directory, which is needed for release testing and benchmarking. This will take twice as long.

  • On the final candidate you just need Release builds, and that’s the binary directory you’ll have to pack.

  • On macOS, you must export MACOSX_DEPLOYMENT_TARGET=10.9 before running the script.

This script builds three phases of Clang+LLVM twice each (Release and Release+Asserts), so use screen or nohup to avoid headaches, since it’ll take a long time.

Use the --help option to see all the options and chose it according to your needs.


Test Suite

Follow the LNT Quick Start Guide link on how to set-up the test-suite

The binary location you’ll have to use for testing is inside the rcN/Phase3/Release+Asserts/llvmCore-REL-RC.install. Link that directory to an easier location and run the test-suite.

An example on the run command line, assuming you created a link from the correct install directory to ~/devel/llvm/install:

./sandbox/bin/python sandbox/bin/lnt runtest \
    nt \
    -j4 \
    --sandbox sandbox \
    --test-suite ~/devel/llvm/test/test-suite \
    --cc ~/devel/llvm/install/bin/clang \
    --cxx ~/devel/llvm/install/bin/clang++

It should have no new regressions, compared to the previous release or release candidate. You don’t need to fix all the bugs in the test-suite, since they’re not necessarily meant to pass on all architectures all the time. This is due to the nature of the result checking, which relies on direct comparison, and most of the time, the failures are related to bad output checking, rather than bad code generation.

If the errors are in LLVM itself, please report every single regression found as blocker, and all the other bugs as important, but not necessarily blocking the release to proceed. They can be set as “known failures” and to be fix on a future date.

Pre-Release Process

When the release process is announced on the mailing list, you should prepare for the testing, by applying the same testing you’ll do on the release candidates, on the previous release.

You should:

  • Download the previous release sources from

  • Run the script on final mode (change -rc 1 to -final).

  • Once all three stages are done, it’ll test the final stage.

  • Using the Phase3/Release+Asserts/llvmCore-MAJ.MIN-final.install base, run the test-suite.

If the final phase’s make check-all failed, it’s a good idea to also test the intermediate stages by going on the obj directory and running make check-all to find if there’s at least one stage that passes (helps when reducing the error for bug report purposes).

Release Process

When the Release Manager sends you the release candidate, download all sources, unzip on the same directory (there will be sym-links from the appropriate places to them), and run the release test as above.

You should:

  • Download the current candidate sources from where the release manager points you (ex.

  • Repeat the steps above with -rc 1, -rc 2 etc modes and run the test-suite the same way.

  • Compare the results, report all errors on Bugzilla and publish the binary blob where the release manager can grab it.

Once the release manages announces that the latest candidate is the good one, you have to pack the Release (no Asserts) install directory on Phase3 and that will be the official binary.

  • Rename (or link) clang+llvm-REL-ARCH-ENV to the .install directory

  • Tar that into the same name with .tar.gz extension from outside the directory

  • Make it available for the release manager to download

Bug Reporting Process

If you found regressions or failures when comparing a release candidate with the previous release, follow the rules below:

  • Critical bugs on compilation should be fixed as soon as possible, possibly before releasing the binary blobs.

  • Check-all tests should be fixed before the next release candidate, but can wait until the test-suite run is finished.

  • Bugs in the test suite or unimportant check-all tests can be fixed in between release candidates.

  • New features or recent big changes, when close to the release, should have done in a way that it’s easy to disable. If they misbehave, prefer disabling them than releasing an unstable (but untested) binary package.