Axis2/C Coding Conventions

1. Naming Conventions

  • Namespace validation is done using the axis2_ prefix.
  • Underscore should be used to separate individual words in identifiers.
  • All identifiers should be meaningful and abbreviations must be avoided whenever possible.

1.1 Variables

  • Use meaningful nouns.
  • Make sure to use all lowercase letters for private and public variables.
  • If it is a local variable or a member of a struct, there's no need to prefix it with axis2_
  • e.g.
int count = 0;
char *prefix = NULL;

1.2 Functions

  • Function names should always start with the prefix axis2_ except for members of a struct.
  • e.g.
axis2_engine_t * axis2_engine_create(axutil_env_t *environment);

1.3 Structures and User Defined Data Types

  • Note the _t suffix in the type name.
  • e.g.
typedef struct axis2_endpoint_ref {
    axis2_char_t *address;
} axis2_endpoint_ref_t;

1.4 Macros

  • Macro names should be in all uppercase letters.
  • e.g.
#define AXIS2_H
#define AXIS2_ERROR_GET_MESSAGE(error) ((error)->ops->get_message(error))

1.5 Enumerations

typedef enum axis2_status_codes {  
    AXIS2_FAILURE = 0,
} axis2_status_codes_t;

2. Indentation and Formatting

    Indentation rules are defined in terms of Artistic Style indent options:
    astyle --style=ansi -b -p -s4 -M0 -c -U -S
    In detail, these options mean,
    • Use the ANSI style code layout
                  int foo()
                      if (is_bar)
                          return 1;
                          return 0;
    • Use spaces around operators
    • Use four spaces for indenting
    • No spaces between the function name and parenthesis
                  if (is_foo(a, b))
                      bar(a, b);
    There are some more formatting guidelines that could not be enforced by a formatting tool, but nevertheless should be followed.
    • Checking pointer validity:
          if (foo)
      and NOT
          if (foo != NULL)
    • Checking equality:
          if (foo == 7)
      and NOT
          if (7 == foo)


    Doxygen style comments should be used to help auto generate API documentation. All structs and functions including parameters and return types should be documented.

4. Function Parameters and Return Value Conventions

    Each function should be passed a pointer to an instance of the axutil_env_t struct as the first parameter. If the function is tightly bound to a struct, the second parameter is a pointer to an instance of that struct.
    Functions returning pointers should return NULL in case of an error. The developer should make sure to set the relevant error code in the environment's error struct.
    Functions that do not return pointer values should always return the AXIS2_FAILURE status code on error whenever possible, or return some other defined error value (in case of returning a struct perhaps). A relevant error code must also be set in the environment's error struct.

5. Include Directives

    It is preferable to include header files in the following fashion:
<standard header files>
<other system headers>
"local header files"