README.coding

**
** Source tree organization
**
******************************************************

There is at least 4 sub-projects in the tree:

 - XBT: eXtended Bundle of Tools (low-level toolbox: logging, datatypes).
 - SURF: a SimUlation aRtiFact. This is the simulation kernel.
 - MSG:  originally MetaSimGrid, MSG is a simple distributed application
         simulator.
 - SMPI: Simulated MPI, to run MPI application using emulation technics.

They are all in the same tree because they are complementary tools and
having all of them in the same package makes the installation easier
for end-users. Moreover, it enables to share the compilation chain and
eases the development.

The tree is not split on projects, but on file finality:
 include/            -> all *public* headers
 include/xbt/*.h     -> one file per module

 src/include -> another location for protected headers. Used by SURF, and
                other should be converted, since this is the Right Thing.

 examples/ -> Supposed to be copy/pastable by the user, so keep it clear and
                avoid any kind of trick. In particular, do only include the
                public headers here.

 teshsuite/ -> The more test the better. Put in there any strange test
               doing things that the users are not supposed to do,
               just to see if our framework is robust to incorrect and
               unusual behaviors. All tests written in this section
               should leverage our tesh(1) utility.

**
** Indentation standard
**
*****************************************************

Most files use the Kernighan & Ritchie coding style with 2 spaces of
indentation. The indent program can help you to stick to it:

indent -kr -l80 -nut -i2 -lps -npcs -br -brs -ce -cdw -bbo -npsl <myfile>

The script ./tools/indent runs indent with the appropriate options.

FIXME: this list of arguments is still to be discussed, maybe

**
** Type naming standard
**
*****************************************************

It may sound strange, but the type naming convention was source of intense
discussion between da SimGrid posse members. The convention we came to may not
be the best solution, but it has the merit to exist and leave everyone work.
So please stick to it.

  - ???_t is a valid type (built with typedef)
  - s_toto_t is a structure (access to fields with .)
  - s_toto   is a structure needing 'struct' keyword to be used
  - e_toto_t is an enum
  - u_toto_t is an union
  - u_toto   is an union needing 'union' keyword to be used
  -   toto_t is an 'object' (struct*)

Please to not call toto_t something else than an 'object' (ie, something you
have to call _new and _free on it).

Example:
  typedef struct s_toto {} s_toto_t, *toto_t;
  typedef enum {} e_toto_t;

Moreover, only toto_t (and e_toto_t) are public. The rest (mainly s_toto_t)
is private.

If you see any part of the code not following this convention, this is a
bug. Please report it (or fix it yourself if you can).

**
** Random bits about coding standards and portability
**
*****************************************************

MALLOC
 Don't use it, or you'll have to check the result (and do some dirty stuff
 on AIX). Use xbt_malloc (or even better, xbt_new) instead.

SIZE_T (FIXME: obsolete?)
 If possible, avoid size_t and use unsigned long instead. If not,
 #include <sys/types.h> in all files manipulating size_t
 do cast it to unsigned long before printing (and use %lu),
 or use %zu.

INTEGERS
 Please avoid to use long ints.  This is the source of many compatibility
 problems between 32 bits and 64 bits archs.  Either use plain ints (generally
 32 bits wide) or long long ints (64 bits wide, at least).  At last resort
 consider using integer types defined in C99 by <stdint.h>.

PRINTF pointer difference (FIXME: advertise %td instead?)
 printf ("diff = %ld\n", (long) (pointer2 - pointer1));

INLINE functions
 The definition of a inline function must be visible when it is used.
 As such, an inline function should be defined (an not only declared)
 in header file (.h) with attributes 'static XBT_INLINE'.  It should
 not be defined in source file (.c).

**
** Commenting the source: doxygen
**
****************************************************

The global structure of the documentation is in doc/modules.doc

The structure of each module (xbt, msg, etc) is in doc/module-<module>.doc

The structure of a module is in its public header. This way, you're sure to
see all the public interface (and only it). The different parts of the
interface are grouped using the @name construct, even if it's buggy. Since
parts often get reordered, it's better to add numbers to the parts (so that
users can see the intended order).

The documentation of each type and macro are also in the public header since
this is were they live.

The documentation of each function must be in the C file were it lives.

Any public element (function, type and macro) must have a @brief part.

**
** XBT virtualization mechanism (FIXME: this section is deprecated)
**
****************************************************

There is some functionalities that we want to virtualize in XBT. We
want xbt_time to give the simulated clock when running on top of the
simulator, and the host clock when running on a real system. This
could be placed in GRAS (and was, historically), but there is some
reason to lower it down to XBT.

Here is the used naming scheme:

  - xbt_<module>_<func>(): functions working both in SG and RL
  - xbt_os_<module>_<func>(): RL functions usable even in simulator

    That way, in libsimgrid, we still can use native functions if we
    want to. It may for example be useful to get the real time when
    implementing the simulator. Think of the SIGINT handler, which
    wants to see if the user pressed the key twice in a 5 seconds
    interval. This is of little use to check the simulated time here.

Here is the file layout:

  - xbt_rl_<module>.c: native implementation (xbt_<module>_<func>()).
    Simply call the corresponding xbt_os_<module>_<func>.
    Part only of libgras.so

  - xbt_sg_<module>.c: SIMIX implementation xbt_<module>_<func>()).
    Simply call the corresponding SIMIX implementation.
    Part only of libsimgrid.so

  - xbt_os_<module>.c: body of the functions implementing natively the
    stuff (xbt_os_<module>_<func>()).
    Part of both libgras.so and libsimgrid.so

Since there is almost nothing in xbt_rl_module.c and xbt_sg_module.c,
it'd be better to use symbol aliasing here (to declare in the object
code that the same function have two names), but I'm still
investigating the portability of the thing to windows.


*
* SimGrid Hacker Survival Guide (FIXME: should be betterly placed)
********************************

* Before pushing any change, don't forget to check if the compilation
  passes with compiler optimizations and warnings turned on:
      cmake -Denable_compile_optimizations=ON \
            -Denable_compile_warnings=ON

* Your commit message should follow the git habits, explained eg here:
  http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html

* When you add/remove files, and/or make changes in the lists of files to build,
  please check that "make distcheck" still succeeds.  This is needed to ensure
  that the generated archive is consistent.

* If you want to debug memory allocation problems, here are a few hints:
  - disable compiler optimizations, to have better backtraces;
  - disable the mallocators, or it will be hard to match malloc's with
    free's;
  - disable model checking, unless your problem lies in the model
    checker part of SimGrid (MC brings its own malloc implementation,
    which valgrind doesn't understand).
  All this is configured with:
      cmake -Denable_model-checking=OFF \
            -Denable_mallocators=OFF \
            -Denable_compile_optimizations=OFF

* If you break the logs (for example while hacking in the dynars), you
  want to define XBT_LOG_MAYDAY at the beginning of log.h. It will
  deactivate the whole logging mechanism, switching to printfs
  instead. SimGrid becomes incredibly verbose when doing so, but it
  you let you fixing the dynars.