
*******************
Style and Workflow
*******************

This document contains normative rules for writing GNUnet
code and naming conventions used throughout the project.


Naming conventions
==================

Header files
------------
.. Not sure if "include" and "header" files are synonymous.


For header files, the following suffixes should be used:

============= ======================================
Suffix        Usage
============= ======================================
``_lib``      Libraries without associated processes
``_service``  Libraries using service processes
``_plugin``   Plugin definition
``_protocol`` structs used in network protocol
============= ======================================

There exist a few exceptions to these rules within the codebase:

* ``gnunet_config.h`` and ``gnunet_directories.h`` are automatically
  generated. 
* ``gnunet_common.h``, which defines fundamental routines
* ``platform.h``, first included. 
  .. I have no idea what that means
* ``gettext.h``, an external library.


Binaries
--------

For binary files, the following convention should be used:

=============================== =========================================
Name format                     Usage
=============================== =========================================
``gnunet-service-xxx``          Service processes (with listen sockets)
``gnunet-daemon-xxx``           Daemon processes (without listen sockets)
``gnunet-helper-xxx[-yyy]``     SUID helper for module xxx
``gnunet-yyy``                  End-user command line tools
``libgnunet_plugin_xxx_yyy.so`` Plugin for API xxx
``libgnunetxxx.so``             Library for API xxx
=============================== =========================================

Logging
-------

The convention is to define a macro on a per-file basis to manage logging:

.. code-block:: c

   #define LOG(kind,...)
   [logging_macro] (kind, "[component_name]", __VA_ARGS__)

The table below indicates the substitutions which should be made 
for ``[component_name]`` and ``[logging_macro]``.

======================== ========================================= ===================
Software category        ``[component_name]``                      ``[logging_macro]``
======================== ========================================= ===================
Services and daemons     Directory name in ``GNUNET_log_setup``    ``GNUNET_log``
Command line tools       Full name in ``GNUNET_log_setup``         ``GNUNET_log``
Service access libraries ``[directory_name]``                      ``GNUNET_log_from``
Pure libraries           Library name (without ``lib`` or ``.so``) ``GNUNET_log_from``
Plugins                  ``[directory_name]-[plugin_name]``        ``GNUNET_log_from``
======================== ========================================= ===================

.. todo:: Clear up terminology within the style guide (_lib, _service mapped to appropriate software categories)

.. todo:: Interpret and write configuration style

Symbols
-------

Exported symbols must be prefixed with ``GNUNET_[module_name]_`` and be
defined in ``[module_name].c``. The only exceptions to this rule are 
symbols defined in ``gnunet_common.h``.

Private symbols, including ``struct``\ s and macros, must not be prefixed.
In addition, they must not be exported in a way that linkers could use them
or other libraries might see them via headers. This means that they must
**never** be declared in ``src/include``, and only declared or defined in 
C source files or headers under ``src/[module_name]``.


Tests
-----

Test cases and performance tests should follow the naming conventions 
``test_[module-under-test]_[test_description].c`` and
``perf_[module-under-test]_[test_description].c``, respectively.

In either case, if there is only a single test, ``[test_description]``
may be omitted.


``src`` subdirectories
----------------------

Subdirectories of ``src`` 



Coding style
============
.. todo:: Examples should follow GNU Coding Standards?

This project follows the GNU Coding Standards.

Indentation is done with two spaces per level, never with tabs.
Specific (though incomplete) indentation rules are defined in an ``uncrustify``
configuration file (in ``contrib``) and are enforced by Git hooks.

.. todo:: Link to uncrustify config in contrib.

C99-style struct initialisation is acceptable and generally encouraged.

.. todo:: Clarify whether there are cases where C99-style struct init is discouraged?

As in all good C code, we care about symbol space pollution and thus use 
:code:`static` to limit the scope where possible, even in the compilation 
unit that contains :code:`main`.

Only one variable should be declared per line:

.. code-block:: c

   // bad
   int i,j;
   
   // good
   int i;
   int j;

This helps keep diffs small and forces developers to think precisely about
the type of every variable.

Note that :c:`char *` is different from :c:`const char*` and
:c:`int` is different from :c:`unsigned int` or :c:`uint32_t`.
Each variable type should be chosen with care.


While ``goto`` should generally be avoided, having a ``goto`` to the
end of a function to a block of clean up statements (free, close,
etc.) can be acceptable.

Conditions should be written with constants on the left (to avoid
accidental assignment) and with the ``true`` target being either the
``error`` case or the significantly simpler continuation. For
example:

::

      if (0 != stat ("filename,"
                     &sbuf))
      {
        error();
      }
      else
      {
        /* handle normal case here */
      }

instead of

::

      if (stat ("filename," &sbuf) == 0) {
        /* handle normal case here */
       } else {
        error();
       }

If possible, the error clause should be terminated with a ``return``
(or ``goto`` to some cleanup routine) and in this case, the ``else``
clause should be omitted:

::

      if (0 != stat ("filename",
                     &sbuf))
      {
        error();
        return;
      }
      /* handle normal case here */

This serves to avoid deep nesting. The 'constants on the left' rule
applies to all constants (including. ``GNUNET_SCHEDULER_NO_TASK``),
NULL, and enums). With the two above rules (constants on left, errors
in 'true' branch), there is only one way to write most branches
correctly.

Combined assignments and tests are allowed if they do not hinder code
clarity. For example, one can write:

::

      if (NULL == (value = lookup_function()))
      {
        error();
        return;
      }

Use ``break`` and ``continue`` wherever possible to avoid deep(er)
nesting. Thus, we would write:

::

      next = head;
      while (NULL != (pos = next))
      {
        next = pos->next;
        if (! should_free (pos))
          continue;
        GNUNET_CONTAINER_DLL_remove (head,
                                     tail,
                                     pos);
        GNUNET_free (pos);
      }

instead of

::

      next = head; while (NULL != (pos = next)) {
        next = pos->next;
        if (should_free (pos)) {
          /* unnecessary nesting! */
          GNUNET_CONTAINER_DLL_remove (head, tail, pos);
          GNUNET_free (pos);
         }
        }

We primarily use ``for`` and ``while`` loops. A ``while`` loop is
used if the method for advancing in the loop is not a straightforward
increment operation. In particular, we use:

::

      next = head;
      while (NULL != (pos = next))
      {
        next = pos->next;
        if (! should_free (pos))
          continue;
        GNUNET_CONTAINER_DLL_remove (head,
                                     tail,
                                     pos);
        GNUNET_free (pos);
      }

to free entries in a list (as the iteration changes the structure of
the list due to the free; the equivalent ``for`` loop does no longer
follow the simple ``for`` paradigm of ``for(INIT;TEST;INC)``).
However, for loops that do follow the simple ``for`` paradigm we do
use ``for``, even if it involves linked lists:

::

      /* simple iteration over a linked list */
      for (pos = head;
           NULL != pos;
           pos = pos->next)
      {
         use (pos);
      }

The first argument to all higher-order functions in GNUnet must be
declared to be of type ``void *`` and is reserved for a closure. We
do not use inner functions, as trampolines would conflict with setups
that use non-executable stacks. The first statement in a higher-order
function, which unusually should be part of the variable
declarations, should assign the ``cls`` argument to the precise
expected type. For example:

::

      int
      callback (void *cls,
                char *args)
      {
        struct Foo *foo = cls;
        int other_variables;

         /* rest of function */
      }

As shown in the example above, after the return type of a function
there should be a break. Each parameter should be on a new line.

It is good practice to write complex ``if`` expressions instead of
using deeply nested ``if`` statements. However, except for addition
and multiplication, all operators should use parens. This is fine:

::

      if ( (1 == foo) ||
           ( (0 == bar) &&
             (x != y) ) )
        return x;

However, this is not:

::

      if (1 == foo)
        return x;
      if (0 == bar && x != y)
        return x;

Note that splitting the ``if`` statement above is debatable as the
``return x`` is a very trivial statement. However, once the logic
after the branch becomes more complicated (and is still identical),
the \"or\" formulation should be used for sure.

There should be two empty lines between the end of the function and
the comments describing the following function. There should be a
single empty line after the initial variable declarations of a
function. If a function has no local variables, there should be no
initial empty line. If a long function consists of several complex
steps, those steps might be separated by an empty line (possibly
followed by a comment describing the following step). The code should
not contain empty lines in arbitrary places; if in doubt, it is
likely better to NOT have an empty line (this way, more code will fit
on the screen).

When command-line arguments become too long (and would result in some
particularly ugly ``uncrustify`` wrapping), we start all arguments on
a new line. As a result, there must never be a new line within an
argument declaration (i.e. between ``struct`` and the struct's name)
or between the type and the variable). Example:

::

      struct GNUNET_TRANSPORT_CommunicatorHandle *
      GNUNET_TRANSPORT_communicator_connect (
        const struct GNUNET_CONFIGURATION_Handle *cfg,
        const char *config_section_name,
        const char *addr_prefix,
        ...);

Note that for short function names and arguments, the first argument
does remain on the same line. Example:

::

      void
      fun (short i,
           short j);


Continuous integration
======================

The continuous integration buildbot can be found at
https://buildbot.gnunet.org. Repositories need to be enabled by a
buildbot admin in order to participate in the builds.

The buildbot can be configured to process scripts in your repository
root under ``.buildbot/``:

The files ``build.sh``, ``install.sh`` and ``test.sh`` are executed in
order if present. If you want a specific worker to behave differently,
you can provide a worker specific script, e.g. ``myworker_build.sh``. In
this case, the generic step will not be executed.

For the ``gnunet.git`` repository, you may use \"!tarball\" or
\"!coverity\" in your commit messages. \"!tarball\" will trigger a
``make dist`` of the gnunet source and verify that it can be compiled.
The artifact will then be published to
https://buildbot.gnunet.org/artifacts. This is a good way to create a
tarball for a release as it verifies the build on another machine.

The \"!coverity\" trigger will trigger a coverity build and submit the
results for analysis to coverity: https://scan.coverity.com/. Only
developers with accounts for the GNUnet project on coverity.com are able
to see the analysis results.

Commit messages and developer branches
======================================

You can find the GNUnet project repositories at https://git.gnunet.org.
For each release, the ChangeLog file is generated from the commit
history. Hence, commit messages are required to convey what changes were
made in a self-contained fashion. Commit messages such as \"fix\" or
\"cleanup\" are not acceptable. You commit message should ideally start
with the subsystem name and be followed by a succinct description of the
change. Where applicable a reference to a bug number in the bugtracker
may also be included. Example:

.. code-block:: text

   # <subsystem>: <description>. (#XXXX)
   IDENTITY: Fix wrong key construction for anonymous ECDSA identity. (Fixes #12344)

If you need to commit a minor fix you may prefix the commit message with
a dash. It will then be ignored when generating the ChangeLog entries:

.. code-block:: text

   # -<text>
   -fix

If you need to modify a commit you can do so using:

.. code-block:: console

   $ git commit --amend

If you need to modify a number of successive commits you will have to
rebase and squash. Note that most branches are protected. This means
that you can only fix commits as long as they are not pushed. You can
only modify pushed commits in your own developer branches.

A developer branch is a branch which matches a developer-specific
prefix. As a developer with git access, you should have a git username.
If you do not know it, please ask an admin. A developer branch has the
format:

::

   dev/<username>/<branchname>

Assuming the developer with username \"jdoe\" wants to create a new
branch for an i18n fix, the branch name could be:

::

   dev/jdoe/i18n_fx

The developer will be able to force push to and delete branches under
his prefix. It is highly recommended to work in your own developer
branches. Code which conforms to the commit message guidelines and
coding style, is tested and builds may be merged to the master branch.
Preferably, you would then\...

-  \...squash your commits,

-  rebase to master and then

-  merge your branch.

-  (optional) Delete the branch.

In general, you may want to follow the rule \"commit often, push tidy\":
You can create smaller, succinct commits with limited meaning on the
commit messages. In the end and before you push or merge your branch,
you can then squash the commits or rename them.
