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[lttng-tools.git] / CodingStyle

LTTng-Tools Coding Style

Author: David Goulet
Last Update: 13/11/2012

Tabs VS Spaces:
-------------

Right, so our two cents in this endless war! This project uses TABS for one
simple reason, the coder can choose whatever size or type his/her indentation
is and can set the prefered coding style by replacing the tabs which each
normally respected IDE/editor can do.

For vim, here is what I used:

  set shiftwidth=4
  set noexpandtab

There is one exception for which  we use space in this project is for enum,
defines and macros values indentation. For instance:

Use space to indent the the value so they fit when reading them all. Same goes
for the #define below.

enum my_enum {
	value1     = 1,
	value289   = 289,
	...
};

#define DEFAULT_VALUE_OF_SOME_SORT   6
#define THE_ANSWER                   42

Use either a single space or tabs to indent the '\' at the end of lines.
Use tabs at the beginning of lines.

Either:

#define a_macro(x) \
	do { \
		fsync(); \
	} while (0)

or

#define a_macro(x)		\
	do {			\
		fsync();	\
	} while (0)

Here is a pretty cool vim macro that will highlight your whitespaces and spaces
before tab. This helps a *LOT* when coding.

" Show trailing whitepace and spaces before a tab:
function MyTrail()
    let no_hl_trail = ["man", "help"]
    if index(no_hl_trail, &ft) >= 0
        return
    endif
    syn match ErrorMsg /\s\+$\| \+\ze\t\|\t\+\ze / containedin=@NoTrail
endfunction
syn cluster NoTrail contains=ALL remove=cComment
autocmd Syntax * call MyTrail()

C Style:
-------------

The coding style used for this project follows the the Linux kernel guide
lines, except that brackets "{", "}" should typically be used even for
single-line if/else statements. Please refer to:

- doc/kernel-CodingStyle.txt (copied from Linux 3.4.4 git tree).

- Linux kernel scripts/checkpatch.pl for a script which verify the patch
  coding style.

For header files, please declare the following in this order:

1) #defines
	- Default values should go in: src/common/defaults.h
	- Macros used across the project: src/common/macros.h

2) Variables
	- No _static_ in a header file! This is madness.
	- Use _extern_ if the global variable is set else where.

3) Function prototype

Furthermore, respect the name spacing of files for each non-static symbol
visiable outside the scope of the C file. For instance, for the utils.c file in
libcommon, every call should be prefixed by "utils_*".

Error handling:
-------------

We ask to use one single return point in a function. For that, we uses the
"goto" statement for the error handling creating one single point for error
handling and return code. See the following example:

int some_function(...)
{
	int ret;
	[...]

	if (ret != 0) {
		goto error;
	}

	[...]
error:
	return ret;
}

Commenting:
-------------

Every function MUST have a comment above it even if the function is trivial.

Please add non-trivial comments/documentation as much as you can in the code.
Poor comments WILL be rejected upon merging so please pay attention to this
details because we do!

If the comments requires more than one line, please format like so:

/*
 * Some comments which requires multiple
 * lines [...]
 */

and on a single line:

/* My comment on a single line. */