mu/HACKING

* HACKING

  Here are some guidelines for hacking on the 'mu' source code.

  This is a fairly long list -- this is not meant to discourage anyone from
  working on mu; I think most of the rules are common sense anyway, and some of
  the more stylistic-aesthetic rules are clearly visible in current source code,
  so as long as any new code 'fits in', it should go a long way in satisfying
  them.

  I should add some notes for the Lisp/Scheme code as well...

** Coding style

   For consistency and, more important, to keep things understandable, mu
   attempts to follow the following rules:

   1. Basic code layout is like in the Linux kernel coding style. Keep the '{'
      on the same line as the statement, except for functions. Tabs for
      indentation, space for alignment; use 8-char tabs.

   2. Lines should not exceed 80 characters (C) or 100 characters (C++)

   3. Functions should not exceed 35 lines (with few exceptions). You can easily
      check if any functions violate this rule with 'make line35', which lists
      all functions with more than 35 non-comment lines.

   4. Source files should not exceed 1000 lines

   5. A function's cyclomatic complexity should not exceed 10 (there could be
      rare exceptions, see the toplevel ~Makefile.am~). You can test the
      cyclomatic complexity with the ~pmccabe~ tool; if you installed that, you
      can use 'make cc10' to list all functions that violate this rule; there
      should be none.

   6. Filenames have their components separated with dashes (e.g, ~mu-log.h~), and
      start with ~mu-~ where appropriate.

   7. Global functions have the prefix based on their module, e.g., ~mu-foo.h~
      declares a function of 'mu_foo_bar (int a);', mu-foo.c implements this.

   8. Non-global functions *don't* have the module prefix, and are declared
      static.

   9. Functions have their return type on a separate line before the function
      name, so:
#+BEGIN_EXAMPLE
      int
      foo (const char *bar)
      {
	....
      }
#+END_EXAMPLE

      There is no non-aesthetic reason for this.

   10. In C code, variable-declarations are at the beginning of a block; in
       principle, C++ follows that same guideline, unless for heavy yet
       uncertain initializations following RAII.

       In C code, the declaration does *not* initialize the variable. This will
       give the compiler a chance to warn us if the variable is not initialized
       in a certain code path.

   11. Returned strings of type char* must be freed by the caller; if they are
       not to be freed, 'const char*' should be used instead

   12. Functions calls have a space between function name and arguments, unless
       there are none, so:

	~foo (12, 3)~;

       and

	~bar();~

       after a comma, a space should follow.

   13. Functions that do not take arguments are explicitly declared as
       f(void) and not f(). Reason: f() means that the arguments are
       /unspecified/ (in C)

   14. C-code should not use ~//~ comments.


** Logging

   For logging, mu uses the GLib logging functions/macros as listed below,
   except when logging may not have been initialized.

   The logging system redirects most logging to the log file (typically,
   ~/.mu/mu.log). g_warning, g_message and g_critical are shown to the user,
   except when running with --quiet, in which case g_message is *not* shown.

   - ~g_message~ is for non-error messages the user will see (unless running with
     ~--quiet~)
   - ~g_warning~ is for problems the user may be able to do something about (and
     they are written on ~stderr~)
   - ~g_critical~ is for mu bugs, serious, internal problems (~g_return_if_fail~ and
     friends use this). (and they are written on ~stderr~)
   - don't use ~g_error~

   If you just want to log something in the log file without writing to screen,
   use ~MU_LOG_WRITE~, as defined in ~mu-util.h~.

** Compiling from git

   For hacking, you're strongly advised to use the latest git version.
   Compilation from git should be straightforward, if you have the right tools
   installed.

*** dependencies

    You need to install a few dependencies; e.g. on Debian/Ubuntu:
#+BEGIN_EXAMPLE
    sudo apt-get install                 \
        automake                         \
        autoconf-archive                 \
        autotools-dev                    \
        libglib2.0-dev                   \
	libxapian-dev			 \
	libgmime-3.0-dev                 \
        m4                               \
        make                             \
        libtool                          \
        pkg-config
#+END_EXAMPLE

   Then, to compile straight from ~git~:

#+BEGIN_EXAMPLE
   $ git clone https://github.com/djcb/mu
   $ cd mu
   $ ./autogen.sh
   $ make
#+END_EXAMPLE

   You only need to run ~./autogen.sh~ the first time and after changes in the
   build system; otherwise you can use ~./configure~.

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