wiki:CodeStyle

Version 5 (modified by Gert Döring, 7 years ago) (diff)

indent cli

This coding style is not final and not yet in effect. Discussion ongoing in #openvpn-devel. Right before branching of the release/2.4 branch, we will have The Great Reformatting where we switch to this coding style.

Introduction

The OpenVPN coding style is based on the Allman style, e.g.:

void myfunction(int a, int b)
{
    if (a == b)
    {
        something_equals();
    }
    else
    {
        does_not_equal();
    }
}

Summarizing:

  • Indentation is 4 spaces, no tabs ever.
  • Opening and closing brackets get their own line, and must match indentation.

Open question: do we allow } else { and } else if () { as exceptions?

  • Line length is 80 characters.
  • C99 is allowed. E.g. for (int i = 0; i < max; i++).
  • Only use /* */-style comments

Open question: should we also allow // for single-line comments now that we can write C99?

Line wrapping

The maximum line length is 80 characters. When lines exceed this length, wrap them using a double indent (ie 8 spaces) on the new line. For example:

void my_function(void)
{
    if (variable_with_artificially_long_name_1 != 0 &&
            variable_with_artificially_long_name_2 != 0)
    {
        return variable_with_artificially_long_name_1 +
                variable_with_artificially_long_name_2 +
                variable_with_artificially_long_name_3;
    }
}

If you find yourself continuously exceeding the line limit, you might want to consider breaking up your function into smaller functions to reduce nesting.

Some additional secure coding style rules

This are style rules, not general secure coding guide lines. See e.g. https://www.securecoding.cert.org/confluence/display/c/SEI+CERT+C+Coding+Standard for useful guidelines on writing secure C.

All branches should use braces

For example:

if (a)
{
    return true;
}

We wouldn't be the first to not spot missing braces in an if statement, like what happened in Apple's goto fail; bug. Always using braces prevents this kind of mistake.

Cases in a switch statement should break or explicitly fall through

The only exception to this rule are empty case statements, to not overly clutter the code with comments.

For example:

switch (a)
{
    case ONE:
    case TWO:
        one_or_two = true;
        /* Fall through */
    case THREE:
        now_do_something();
        break;
    default:
        ASSERT(0);
}

This makes the intent immediately clear to the reader / reviewer.

GNU Indent rules

to get the above effect, use

gindent -kr -bl -nce file.c

(though other options might be needed, work in progress)