Notice

This is a modification of the style guide provided by [suckless.org].

File Layout

• Comment with LICENSE
• Headers
• Macros
• Types
• Function declarations
  • Include variable names
  • For short files these can be left out
  • Group/order in logical manner
• Global variables
• Function definitions in same order as declarations
• main

C Features

• Up to C99 without extensions
• POSIX.1-2008
• Declarations should not be mixed with statements
• Loop initial declarations should not used
• C style /* */ comments should be used, not C++ style // comments
• #if 0 #endif must be used to comment out code, not /* */
• Variadic functions and macros are acceptable, but require safety

Blocks

• { on same line preceded by single space (except functions)

• } on own line unless continuing statement (e.g. if else)

• Blocks are used for single statements if and only if

  • An inner statement needs a block:

    for (;;) {
        if (foo) {
            bar;
            baz;
        }
    }
    

  • Another branch of the same statement needs a block:

    if (foo) {
        bar;
    } else {
        baz;
        qux;
    }
    

  • One exception to this rule is nested for loops like below:

    for (i = 0; i < 64; ++i)
    for (j = 0; j < 32; ++j)
    for (k = 0; k < 16; ++k) {
        /* ... do stuff here ... */
    }
    

Indentation and Line Length

• The maximum line length is 80 columns
• Tabs are used for indentation with a visual width 8-spaces
• An extra indent or two should be used when wrapping lines
• String literals used in error messages are an exception to these rules:
  • This makes them easy to search for with grep
• Multiline string literals should be continued with \

Functions

• Modifiers and the return type on their own line
• Function name and argument list on the next line
• Opening { must be on its own line (functions are special)
• Functions not used outside translation unit must be static

Variables

• Should be declared as close as possible to initialization/use

• Global variables not used outside translation unit should be static

• In declaration of pointers the * must be touching the variable name, not the type:

  int *foo;
  

Keywords

• Space after if, for, while, and switch as these are not function calls
• Space should not be used after the opening ( and before the closing )
• Parentheses must be used with sizeof
• sizeof() must be written as a function call since it acts like one
• switch statements and their cases share the same indentation level
• switch cases that FALLTHROUGH should be commented

Headers

• Include libc/system headers come first alphabetically
  • If order cannot be alphabetical, a comment must explain
• There must be a blank line between system headers and project headers
• When writing and using local headers
  • Include guards must be used
  • Should be included alphabetically

User Defined Types

• Typedef is not used for structs which have fields meant to be accessed
• Typedef is allowed for opaque types, enums, and error codes
• Type names should be all lowercase

Handling Errors

• Use Linux style gotos in a function that can fail and must cleanup multiple resources before exiting

• Errors or failures should be returned from early rather than later in nested code:

  • Like so:

    if (err)
        return;
    

  • Instead of:

    if (success) {
        /* Do stuff */
    } else {
        return;
    }
    

Enums vs #define

• Use enums for values that are grouped semantically and #define otherwise:

  #define MAXSZ  4096
  #define MAGIC1 0xdeadbeef
  
  
  enum {
      DIRECTION_X,
      DIRECTION_Y,
      DIRECTION_Z
  };