android13/external/libabigail/CONTRIBUTING

Contact
=======

The project homepage is at https://sourceware.org/libabigail

The current libabigail source code can be checked out with:
git clone git://sourceware.org/git/libabigail

The mailing list to send messages and patches to is
libabigail@sourceware.org.

The archives of that list are available at http://sourceware.org/ml/libabigail.

File bugs
=========

Bugs are to be filled in bugzilla at
https://sourceware.org/bugzilla/enter_bug.cgi?product=libabigail

Writing and sending patches
============================

Please supply patches using git format-patch and git send-email.  If
you don't know how to use git, send-email, fine.  Just use your
favorite email client, attach the patch to a nice message, and send us
the message.

Patches have to be sent by email to libabigail@sourceware.org.

Please read the file COMMIT-LOG-GUIDELINES in the source tree to learn
about how to write the commit log accompanying the patch.

If you are adding a new public header file to the project, or if you
are defining a new entry point to the API of libabigail, please take
some time to read the file VISIBILITY about how you need to handle the
visibility of symbols that are part of the API and ABI of libabigail.

Make sure you sign your patch.  To learn about signing, please read
the "Sign your work" chapter below.

One important thing to do before sending your patch is to launch the
regression tests.

Regression tests
================

Regression tests are under the directory 'tests'.  They are usually
written in C++ and are especially designed to be easy to debug.  The
idea is that if the test fails, the programmer should just have to
launch them under GDB and debug them right away.  No-bullshit style.

Regression tests are launched by doing:

   make check

If you have N processor cores on your machine, you can launch the
tests in parallel to make whole thing go faster by doing:

  make -jN -lN check

If you want to test the fabrication of the distribution tarball (this
is important, because that is how we do to actually release the
tarball of the project that you can download from the internet) then
you can do:

  make distcheck-fast

This actually builds the tarball, then untars it, configure/compile
the untarred source code and launches the regression checks from
there.

Here, "make distcheck-fast" is a variant of the standard "make distcheck".
It compresses with "--fast" instead of default "--best", and is
significantly faster, given the size of the distribution.  You very likely
want to use that one for local regression testing.  (However, don't use
"make distcheck-fast" to create artifacts for distribution.)

You can also launch this in parallel by doing:

  make -jN -lN distcheck-fast

with N being the number of processor core you have on your system.

Please make sure you always launch "make distcheck-fast" before sending a
patch, so that you are sure that we can always build a tarball after
your patch is applied to the source tree.

A complementary regression checking target is "check-self-compare".
You invoke it by doing "make check-self-compare".  That target
analyzes the ABI of the libabigail.so shared object, serializes it
into the ABIXML format and then compares the ABI internal
representation gathered from the libabigail.so binary against the one
gathered from the ABIXML format.  The two should be equal if
everything goes right.  This is an important regression test.  The
problem is that it can take a considerable amount of time.
So we've put it into its own separate target.

So, to be complete the regression checking command to run against your
patch should be: "make check-self-compare distcheck-fast -j16", if you have
a machine with a 16 threads processors, for instance.

Launching regression tests in Valgrind
--------------------------------------

To detect memory management errors, the tests of the regression test
suite can be run using Valgrind tools, essentially memcheck and
helgrind.

To do so, please do:

  make check-valgrind

This runs the tests under the control of Valgrind memcheck and
helgrind tools.

But then, if you want Valgrind to check the libabigail command line
tools that are *forked* by some of the tests then type:

  make check-valgrind-recursive

This one takes a long time.  On my system for instance, it takes an
hour.  But then it checks *everything*.  If you don't have that time,
then "make check-valgrind" is enough, as the regression tests that use
the libabigail *library* directly (as opposed to forking libabigail
command line tools) will be verified.

How tests are organized
-----------------------

There are two kinds of regression tests.  Those that use the
libabigail *library* directly, and those that spawn one of the
libabigail command line tools.

Generally, both are usually made of a loop that churns through a set of input
binaries to compare.  Once the comparison is done, the resulting
report is compared against a reference report that is provided.

Test executable have names that starts with 'runtest*'.  For instance,
under <build-directory>/tests/ you can find tests named
runtestdiffdwarf, runtestabidiff, etc...

If a test executable is named
<build-directory>/tests/runtestdiffdwarf, then its source code is
tests/test-diff-dwarf.cc.  Similarly, the source code of the test
<build-directory>/tests/runtestabidiff is tests/test-abidiff.cc.

The data provided for each test (for instance the input binaries to
compare and the reference report that should result from the
comparison) is to be found under tests/data.  So data for the test
runtestdiffdwarf is to be found under tests/data/test-diff-dwarf.
Data for the test runtestabidiff is to be found under
tests/data/test-abidiff.cc.

So adding your own tests usually just amounts to adding the input
right input into the right sub-directory of tests/data/.  To do so,
look at several tests/test-*.cc to see which one you'd like to add
some input binaries to be compared in.

Then once you know which tests/test-*.cc you'd like to extend, and if
you added your input binaries and reference reports (maybe other
things too) to the right sub-director of tests/data/, you just need to
extend the array of input binaries/reference reports that the test
walks to perform the comparisons.  It's generally a global variable
before the main() function of the test.  In test-diff-dwarf.cc, for
instance, the variable name is "in_out_specs".  You just have to add a
new entry to that array; that new entry contains the paths to your new
input binaries and reference reports.  Just read the code in there and
use your brains.  It should be straight forward.

Ah, also, if you added new files for the tests, then the build system
needs to be told that those files have to be added to the distribution
tarball when we do "make dist" (or make distcheck).  To do so, please
make sure to add your new test input files to the
tests/data/Makefile.am file, in the EXTRA_DIST variable.  Look at how
things are organized in that file, and please do things similarly.

fedabipkgdiff testing
---------------------

This depends on the Python koji and a few support modules.  If these are
not available, 'configure' disables fedabipkgdiff and its 'make check'
testing.

Debian and Ubuntu, for example, don't provide packages for the Python
koji module.  If you'd like to run fedabipkgdiff testing without manually
doing a proper Koji installation, you may simply download Koji sources
(<https://pagure.io/koji>, releases, or Git clone) and point to these via
the Python search path.  For example, tested 2021-12-11:

  wget https://pagure.io/koji/archive/koji-1.27.0/koji-koji-1.27.0.tar.gz
  tar -xzf koji-koji-1.27.0.tar.gz
  export PYTHONPATH="$PWD"/koji-koji-1.27.0

A libabigail 'configure' run then enables fedabipkgdiff and its
'make check' testing.

Coding language and style
==========================

The coding style is self evident when reading the source code.  So
please, stick to and mimic what is already in there for the sake of
consistency at very least.  Just for history, it's derived from the
style of the C++ standard library from the GNU project.

As of libabigail 2.0, the language we use is C++ 11.  The level
supported is the one supported by the GCC 4.8.x series of compilers.
This should be old and well tested enough to be supported by your
current favorite compiler.

Initially, the code base of the project was written in C++03, with the
TR1 extensions.  That heritage is well visible in the code base as it
is today.

Please do not rush and send gazillions of patches that just re-write
tons of code into your favorite C++ 11 flavour du jour.  We will
likely reject those patches.  We want to keep the history of the code
base in such a way that tools like "git blame <sourcefile> are still
useful.

So we'll accept patches changing parts of the code base to more recent
C++ 11 constructs only if you happen to add functionality or fix
things in that area.  If it makes "cultural common" sense to adopt
those constructs.  What I mean by "cultural" is that must make sense
in relative to the culture of the project.  And yes, that is
subjective.  Sorry.

As a generic rule, we tend to favor the lowest possible level of
abstraction that makes sense without requiring future maintainers of
the project to have a PhD in design patterns.  We are not impressed by
design patterns.  We use them where they make clear sense, but we
don't idolize them.  Put it another way, we will always favor the one
who *READS* and debug the code over the one who writes it.  To put
things in a hypothetical perspective, we'll rather accept a repetitive
code that stays simple to read and debug over a highly abstract one
using meta programming to save a few lines of repetitive code located
in a very small number of places.

Really, in this project, we care about low level binary analysis
stuff.  Issues in that area can be hard to reproduce and quite
challenging to debug.  So having tons of abstraction layers in the
code base have proven to be a maintenance burden over the years, from
our experience in working on similar projects.  So please help us
avoid those mistakes that we make just for the pleasure of writing
what can look as "pleasant code" at a first naive sight.

That being said, we also love cleanly designed APIs that are fairly
re-usable and well documented.  And we also praise abstraction and
modularisation that we recognize as being the most basic tools of any
engineer.  So we like to think about ourselves as well rounded people
who care about maintaining things for a long time to come :-)

Sign your work
==============

To facilitate tracking of who did what, we've adopted a "sign-off"
procedure for patches based on the procedure used by the Linux kernel
project.

The sign-off is a simple line at the end of the explanation for the
patch, which certifies that you wrote it or otherwise have the right
to pass it on as a patch under an appropriate license. The rules are
pretty simple: if you can certify the below:

        Developer's Certificate of Origin

        By making a contribution to this project, I certify that:

	(a) The contribution was created in whole or in part by me,
	    and I have the right to submit the contribution under the
	    license indicated in, or otherwise designated as being
	    applicable to, the file.

        (b) The contribution was provided directly to me by some other
            person who certified (a), and I have not modified it.

        (c) I understand and agree that the project and the
            contribution are public and that a record of the
            contribution (including all personal information I submit
            with it, including my sign-off) is maintained indefinitely
            and may be redistributed.

then you just add a line saying

Signed-off-by: Random J Developer <random@developer.example.org>

using your real name (sorry, no pseudonyms or anonymous contributions.)

git commit --signoff will add such a Signed-off-by line at the end of
the commit log message for you.

Modifying the website
=====================

The source code of the website of libabigail is stored in CVS (sigh,
yeah, that is so old school).  You can check out that web source code
by doing:

    CVS_RSH=ssh cvs -z9 -d :ext:user@sourceware.org:/cvs/libabigail/ co htdocs

where 'user' is your username on the sourceware system.
Alternatively, you can check out the the web source code anonymously,
if you don't have any user account on the sourceware system by doing:

    export CVSROOT=:pserver:anoncvs@cygwin.com:/cvs/libabigail
    cvs login
    (the CVS anonymous password to use is "anoncvs")
    cvs checkout htdocs


Happy Hacking!