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rust/README.rst
author Augie Fackler <augie@google.com>
Fri, 06 Dec 2019 15:19:47 -0500
changeset 43813 5a9e2ae9899b
parent 35569 964212780daf
child 44114 8a3b045d9086
permissions -rw-r--r--
fuzz: use a more standard approach to allow local builds of fuzzers This is taken from the (improved since we started fuzzing) guide on ideal integrations. Rather than have our own wonky targets for building outside the fuzzer universe, we have a driver program we carry along and use when we're not using LibFuzzer. This will let us jettison a fair amount of goo. contrib/fuzz/standalone_fuzz_target_runner.cc is https://github.com/google/oss-fuzz/ file projects/example/my-api-repo/standalone from git revision c4579d9358a73ea5dbcc99cb985de1f2bf76dcf7, reformatted with out clang-format settings and a no-check-code comment added. It allows running a single test input through a fuzzer, rather than performing ongoing fuzzing as libfuzzer would. contrib/fuzz/FuzzedDataProvider.h is https://github.com/llvm/llvm-project/ file /compiler-rt/include/fuzzer/FuzzedDataProvider.h from git revision a44ef027ebca1598892ea9b104d6189aeb3bc2f0, reformatted with our clang-format settings and a no-check-code comment added. We can discard this if we instead want to add an hghave check for a new enough llvm that includes FuzzedDataProvder.h in the fuzzer headers. Differential Revision: https://phab.mercurial-scm.org/D7564

===================
Mercurial Rust Code
===================

This directory contains various Rust code for the Mercurial project.

The top-level ``Cargo.toml`` file defines a workspace containing
all primary Mercurial crates.

Building
========

To build the Rust components::

   $ cargo build

If you prefer a non-debug / release configuration::

   $ cargo build --release

Features
--------

The following Cargo features are available:

localdev (default)
   Produce files that work with an in-source-tree build.

   In this mode, the build finds and uses a ``python2.7`` binary from
   ``PATH``. The ``hg`` binary assumes it runs from ``rust/target/<target>hg``
   and it finds Mercurial files at ``dirname($0)/../../../``.

Build Mechanism
---------------

The produced ``hg`` binary is *bound* to a CPython installation. The
binary links against and loads a CPython library that is discovered
at build time (by a ``build.rs`` Cargo build script). The Python
standard library defined by this CPython installation is also used.

Finding the appropriate CPython installation to use is done by
the ``python27-sys`` crate's ``build.rs``. Its search order is::

1. ``PYTHON_SYS_EXECUTABLE`` environment variable.
2. ``python`` executable on ``PATH``
3. ``python2`` executable on ``PATH``
4. ``python2.7`` executable on ``PATH``

Additional verification of the found Python will be performed by our
``build.rs`` to ensure it meets Mercurial's requirements.

Details about the build-time configured Python are built into the
produced ``hg`` binary. This means that a built ``hg`` binary is only
suitable for a specific, well-defined role. These roles are controlled
by Cargo features (see above).

Running
=======

The ``hgcli`` crate produces an ``hg`` binary. You can run this binary
via ``cargo run``::

   $ cargo run --manifest-path hgcli/Cargo.toml

Or directly::

   $ target/debug/hg
   $ target/release/hg

You can also run the test harness with this binary::

   $ ./run-tests.py --with-hg ../rust/target/debug/hg

.. note::

   Integration with the test harness is still preliminary. Remember to
   ``cargo build`` after changes because the test harness doesn't yet
   automatically build Rust code.
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