C Naming Conventions

File names should use snake_case.

hello_world.c
useful_header.h

Preprocessor include guards should be the same as the file name, replacing '.' with _, with the addition of two underscores __ on either side.

#define __SOME_FILE_H__   // some_file.h

Preprocessor macro names should use SCREAMING_SNAKE_CASE

#define I_AM_DEFINED
#define CONSTANT_FOO 1
#define MACRO_BAR(X) bar(X)

Variable names should use snake_case.

int some_var_name;

Pointers should be postfixed with _p. A pointer to a pointer should be postfixed with _pp, and so on.

int*  pointer_p;
int** double_pointer_pp;

Boolean variables should be signed ints prefixed with b_.

int b_boolean;

Array variables should be postfixed with _arr, regardless of whether array subscript notation or pointer notation is used. Variables that are used to store the length of arrays should be named after the array they are associated with followed by _arr_n.

int    array_of_ints_arr[];
size_t array_of_ints_arr_n;
float* array_of_floats_arr;

Character arrays used for the purpose of storing strings should be postfixed with _str. Variables that are used to store the length of strings (excluding any terminating character) should be postfixed with _len.

char*  a_string_str;
size_t a_string_len;

Function names should use snake-case. If a function takes no parameters, then void should be specified in the parameter list to conform to strict prototypes.

void some_function(void);

struct identifiers should be postfixed with _st. A single underscore _ is used to denote members of a struct which are not meant to be modified by the user.

struct struct_name_st {
  int some_member_var;
  int _readonly_member_var;
};

enum identifiers should be postfixed with _en. All members of an enum should be prefixed with the enum's name in uppercase, followed by the enum member's unique name in snake-case. An optional member at the end of an enum may be desired in some cases to get the maximum value of an enum. This value identifer should be prixed with __MAX.

enum enum_name_en {
  ENUM_NAME_one,
  ENUM_NAME_two,
  ENUM_NAME_three,

  // Optional
  ENUM_NAME__MAX
};

Generally it should be preferred to use a symbol's fully qualified name, but if a typedef alias is necessary, then the identifier should be postfixed with _ty.

typedef type type_alias_ty;

Function pointer names should be prefixed with f_.

void(*f_function_pointer)();