c.md

C

Notez Bien: All these rules are meant to be broken, BUT you need a very good reason AND you must explain it in a comment.

Style

Names (TL;DR)

• function_name, _static_function_name, MACRO_NAME, StructName, new_type_t, NEW_TYPE_ALT, GlobalVarName, _StaticGlobalVarName, local_var_name, t, function_param_name.

General

• Follow this order for the sections inside source files: system includes, project-specific includes, struct and type definitions, prototypes, global variables with external linkage, global variables with internal linkage, functions. Always use prototypes, functions order inside the file should be irrelevant.
• Don't start identifiers with a double underscore (int __foo;), don't shadows identifiers from the standard libraries (int printf = 23;). Don't rename the arguments of main (use argc and argv). Don't use single-character identifiers that could be misinterpreted on a printout (l, O).
• Use nouns for variables, full sentences for functions (factors = factorize(formula);); predicates (i.e., functions returning a boolean value) should start with the is_ prefix (if is_gargled(quz) { ... }).
• Use long comprehensible names for global variables. Use long comprehensible names for local variables that may be meaningful in different part of the code; declare such variables in the beginning of the function, but initialize them the closest possible to their first usage. Use very short names for variables with limited semantic span; declare and initialize them in the smallest possible scope.

int  last_useful_index;
// several lines...
last_useful_index = -1;
for(int t = 0; t < NUM_ELEMENT; ++t) {
    int u = complex_function(GlobalData[t]);
    another_complex_function(u);
    if(is_useful(u) {
        last_useful_index = t;
    }
}

• Declare structs in the beginning of the source file. If a struct is only useful as a local variable in a function, don't assign it any name.

• Typedefs names can be either in all capitals (BYTE) or ending with a _t (byte_t), try to be consistent in each project. It is possible to typedef struct _FOO { ... } FOO; instead of typedef struct { ... } FOO; if struct _FOO is required.

• Declare multiple variables on the same line to stress that they are strongly related (int pos_x, pos_y;). Also consider using a struct in such cases.

• Keep the asterisk attached to the variable name when declaring a pointer (FILE *foo;).

• Use a K&R style for indenting the code. Suggested: the Linux kernel variant with tabs replaced by 4 spaces.