Difference between revisions of "Code Conventions"

From VideoLAN Wiki
Jump to navigation Jump to search
(Add some notes about Objective C)
Line 79: Line 79:
Group your class, if it makes sense using pragma marks:
Group your class, if it makes sense using pragma marks:
<source lang="c">
<source lang="objc">
#pragma mark -
#pragma mark -
#pragma mark Helper methods
#pragma mark Helper methods

Latest revision as of 00:11, 7 February 2017


The following conventions are the 'classical' VLC code conventions. Those are not enforced anymore.

The important is to keep consistency of codestyle when you modify a file.

If you write a new file, select your style. Common used styles are VLC Style and K&R.

Code conventions

Here you find conventions about how the VLC media player developers write their code.

Function naming

All functions are named accordingly: module name (in lower case) + _ + function name (in mixed case, without underscores). For instance: intf_FooFunction. Static functions don't need the module name.

Variable naming

We use Hungarian notation. That is, we have the following prefixes:

  • i_ for integers (sometimes l_ for long integers)
  • b_ for booleans
  • d_ for doubles
  • f_ for floats
  • Generally, we add a p when the variable is a pointer to a type
    • pf_ for function pointers
    • psz_ for a pointer to a string terminated by a zero (C-string)

If a variable has no basic type (for instance a complex structure), don't put any prefix (except p_ if it's a pointer). After one prefix, put an explicit variable name in lower case. If several words are required, join them with an underscore (no mixed case).


  • data_packet_t * p_buffer
  • char psz_msg_date[42]
  • int pi_es_refcount[MAX_ES];
  • void (* pf_next_data_packet)( int * )

A few words about white space


Never use tabs in the source (nevertheless you're entitled to use them in the Makefile :-).

Use set expandtab under vim or the equivalent under emacs.

Indents are 4 spaces long.


Put spaces before and after operators, and inside brackets. For instance:

for( i = 0; i < 12; i++, j += 42 ); 


Leave braces alone on their lines (GNU style[1]). For instance:

if( i_es == 42 )
   p_buffer[0] = 0x12;


ANSI C-style comments /* ... */ are more commonly used for historical reasons, though C++/C99 comments are tolerated, but please don't mix both in the same file.

Qt interface added conventions


Objective-C conventions

For new Objective-C code, do not use Hungarian notation, unless you are editing a file that still uses it. Use cameCase for properties and methods, as usual.

When adding new classes, make sure to state in the leading comment block what the use-case for that class is.

Try to document your methods with doxygen comments, where it makes sense, see VLCRendererDiscovery.h for an example.

Group your class, if it makes sense using pragma marks:

#pragma mark -
#pragma mark Helper methods

Partial availability

If you call a method that is only available since a specific macOS version, make sure that you implement a proper fallback (if necessary). Add a preprocessor #ifdef to preven compilation with SDKs that do not define the method. Add a runtime check to make sure the method is not called in macOS versions that do not have it. Check out the example below:

#ifdef MAC_OS_X_VERSION_10_10
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wpartial-availability"
    /* Calling a method that is only available on macOS 10.10 or later */
} else {
    /* Call the replacement for specific method, if necessary */

#pragma clang diagnostic pop

/* Built with SDK that does not declare the necessary headers, always calling the replacement */


(Avoid this, only do it if it is really necessary)