.. _build_toolchains:

===========================
Creating Toolchain Archives
===========================

There are various scripts in the repository for producing archives
of the build tools (e.g. compilers and linkers) required to build.

Clang and Rust
==============

To modify the toolchains used for a particular task, you may need several
things:

1. A `build task`_

2. Which uses a toolchain task

    - `clang toolchain`_
    - `rust toolchain`_

3. Which uses a git fetch

    - `clang fetch`_
    - (from-source ``dev`` builds only) `rust fetch`_

4. (clang only) Which uses a `config json`_

5. Which takes patches_ you may want to apply.

For the most part, you should be able to accomplish what you want by
copying/editing the existing examples in those files.

.. _build task: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/build/linux.yml#5-45
.. _clang toolchain: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/toolchain/clang.yml#51-72
.. _rust toolchain: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/toolchain/rust.yml#57-74
.. _clang fetch: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/fetch/toolchains.yml#413-418
.. _rust fetch: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/fetch/toolchains.yml#434-439
.. _config json: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/build/build-clang/clang-linux64.json
.. _patches: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/build/build-clang/static-llvm-symbolizer.patch

Clang
-----

Building clang is handled by `build-clang.py`_, which uses several resources
in the `build-clang`_ directory. Read the `build-clang README`_ for more
details.

Note for local builds: build-clang.py can be run on developer machines but its
lengthy multi-stage build process is unnecessary for most local development. The
upstream `LLVM Getting Started Guide`_ has instructions on how to build
clang more directly.

.. _build-clang.py: https://searchfox.org/mozilla-central/source/build/build-clang/build-clang.py
.. _build-clang README: https://searchfox.org/mozilla-central/source/build/build-clang/README
.. _build-clang: https://searchfox.org/mozilla-central/source/build/build-clang/
.. _LLVM Getting Started Guide: https://llvm.org/docs/GettingStarted.html

Rust
----

Rust builds are handled by `repack_rust.py`_. The primary purpose of
that script is to download prebuilt tarballs from the Rust project.

It uses the same basic format as `rustup` for specifying the toolchain
(via ``--channel``):

- request a stable build with ``1.xx.y`` (e.g. ``1.47.0``)
- request a beta build with ``beta-yyyy-mm-dd`` (e.g. ``beta-2020-08-26``)
- request a nightly build with ``nightly-yyyy-mm-dd`` (e.g. ``nightly-2020-08-26``)
- request a build from `Rust's ci`_ with ``bors-$sha`` (e.g. ``bors-796a2a9bbe7614610bd67d4cd0cf0dfff0468778``)
- request a from-source build with ``dev``

Rust From Source
----------------

As of this writing, from-source builds for Rust are a new feature, and not
used anywhere by default. The feature was added so that we can test patches
to rustc against the tree. Expect things to be a bit hacky and limited.

Most importantly, building from source requires your toolchain to have a
`fetch of the rust tree`_ as well as `clang and binutils toolchains`_. It is also
recommended to upgrade the worker-type to e.g. ``b-linux-large``.

Rust's build dependencies are fairly minimal, and it has a sanity check
that should catch any missing or too-old dependencies. See the `Rust README`_
for more details.

Patches are set via `the --patch flag`_ (passed via ``toolchain/rust.yml``).
Patch paths are assumed to be relative to ``/build/build-rust/``, and may be
optionally prefixed with ``module-path:`` to specify they apply to that git
submodule in the Rust source. e.g. ``--patch src/llvm-project:mypatch.diff``
patches rust's llvm with ``/build/build-rust/mypatch.diff``. There are no
currently checked in rust patches to use as an example, but they should be
the same format as `the clang ones`_.

Rust builds are not currently configurable, and uses a `hardcoded config.toml`_,
which you may need to edit for your purposes. See Rust's `example config`_ for
details/defaults. Note that these options do occasionally change, so be sure
you're using options for the version you're targeting. For instance, there was
a large change around Rust ~1.48, and the currently checked in config was for
1.47, so it may not work properly when building the latest version of Rust.

Rust builds are currently limited to targeting only the host platform.
Although the machinery is in place to request additional targets, the
cross-compilation fails for some unknown reason. We have not yet investigated
what needs to be done to get this working.

While Rust generally maintains a clean tree for building ``rustc`` and
``cargo``, other tools like ``rustfmt`` or ``miri`` are allowed to be
transiently broken. This means not every commit in the Rust tree will be
able to build the `tools we require`_.

Although ``repack_rust`` considers ``rustfmt`` an optional package, Rust builds
do not currently implement this and will fail if ``rustfmt`` is busted. Some
attempt was made to work around it, but `more work is needed`_.

.. _Rust's ci: https://github.com/rust-lang/rust/pull/77875#issuecomment-736092083
.. _repack_rust.py: https://searchfox.org/mozilla-central/source/taskcluster/scripts/misc/repack_rust.py
.. _fetch of the rust tree: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/toolchain/rust.yml#69-71
.. _clang and binutils toolchains: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/ci/toolchain/rust.yml#72-74
.. _the --patch flag: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/scripts/misc/repack_rust.py#667-675
.. _the clang ones: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/build/build-clang/static-llvm-symbolizer.patch
.. _Rust README: https://github.com/rust-lang/rust/#building-on-a-unix-like-system
.. _hardcoded config.toml: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/scripts/misc/repack_rust.py#384-421
.. _example config: https://github.com/rust-lang/rust/blob/b7ebc6b0c1ba3c27ebb17c0b496ece778ef11e18/config.toml.example
.. _tools we require: https://searchfox.org/mozilla-central/rev/168c45a7acc44e9904cfd4eebcb9eb080e05699c/taskcluster/scripts/misc/repack_rust.py#398
.. _more work is needed: https://github.com/rust-lang/rust/issues/79249


Windows
=======

The ``build/windows_toolchain.py`` script is used to build and manage
Windows toolchain archives containing Visual Studio executables, SDKs,
etc.

The way Firefox build automation works is an archive containing the
toolchain is produced and uploaded to an internal Mozilla server. The
build automation will download, verify, and extract this archive before
building. The archive is self-contained so machines don't need to install
Visual Studio, SDKs, or various other dependencies. Unfortunately,
Microsoft's terms don't allow Mozilla to distribute this archive
publicly. However, the same tool can be used to create your own copy.

Configuring Your System
-----------------------

It is **highly** recommended to perform this process on a fresh installation
of Windows 7 or 10 (such as in a VM). Installing all updates through
Windows Update is not only acceptable - it is encouraged. Although it
shouldn't matter.

Next, install Visual Studio 2017 Community. The download link can be found
at https://www.visualstudio.com/vs/community/.
Be sure to follow these install instructions:

1. Choose a ``Custom`` installation and click ``Next``
2. Select ``Programming Languages`` -> ``Visual C++`` (make sure all sub items are
   selected)
3. Under ``Windows and Web Development`` uncheck everything except
   ``Universal Windows App Development Tools`` and the items under it
   (should be ``Tools (1.3.1)...`` and the ``Windows 10 SDK``).

Once Visual Studio 2017 Community has been installed, from a checkout
of mozilla-central, run something like the following to produce a ZIP
archive::

   $ ./mach python build/windows_toolchain.py create-zip vs2017_15.8.4

The produced archive will be the argument to ``create-zip`` + ``.zip``.

Firefox for Android with Gradle
===============================

To build Firefox for Android with Gradle in automation, archives
containing both the Gradle executable and a Maven repository
comprising the exact build dependencies are produced and uploaded to
an internal Mozilla server.  The build automation will download,
verify, and extract these archive before building.  These archives
provide a self-contained Gradle and Maven repository so that machines
don't need to fetch additional Maven dependencies at build time.
(Gradle and the downloaded Maven dependencies can be both
redistributed publicly.)

Archiving the Gradle executable is straight-forward, but archiving a
local Maven repository is not.  Therefore a toolchain job exists for
producing the required archives, `android-gradle-dependencies`.  The
job runs in a container based on a custom Docker image and spawns a
Sonatype Nexus proxying Maven repository process in the background.
The job builds Firefox for Android using Gradle and the in-tree Gradle
configuration rooted at ``build.gradle``.  The spawned proxying Maven
repository downloads external dependencies and collects them.  After
the Gradle build completes, the job archives the Gradle version used
to build, and the downloaded Maven repository, and exposes them as
Task Cluster artifacts.

To update the version of Gradle in the archive produced, update
``gradle/wrapper/gradle-wrapper.properties``.  Be sure to also update
the SHA256 checksum to prevent poisoning the build machines!

To update the versions of Gradle dependencies used, update
``dependencies`` sections in the in-tree Gradle configuration rooted
at ``build.gradle``.  Once you are confident your changes build
locally, push a fresh build to try.  The `android-gradle-dependencies`
toolchain should run automatically, fetching your new dependencies and
wiring them into the appropriate try build jobs.

To update the version of Sonatype Nexus, update the `sonatype-nexus`
`fetch` task definition.

To modify the Sonatype Nexus configuration, typically to proxy a new
remote Maven repository, modify
`taskcluster/scripts/misc/android-gradle-dependencies/nexus.xml`.

There is also a toolchain job that fetches the Android SDK and related
packages.  To update the versions of packaged fetched, modify
`python/mozboot/mozboot/android-packages.txt` and update the various
in-tree versions accordingly.