Style guidelines for `configure.ac`

Version 2019.08.09.21.54

Purpose

Define a small set of rules for style used in Expat's configure.ac so that we have a commen ground and something documented to refer to in pull requests, when style is off.

1. Quoting

Quote “everything”:

AC_DEFINE([HAVE_FOO], [1], [Define to 1 if you have the `foo' function.])

2. Parameter indentation

Parameters to functions either go

(a) on the the same line or
(b) align vertically or
(c) go to the next line, with the first character indented 2 spaces more than the first non-[(!) parent level character, i.e. 2 or 3 columns further right:

CALL([parameter], [parameter], [parameter])

CALL([parameter],
     [parameter],
     [parameter])

CALL([parameter], [parameter],
  [CALL(
     [CALL()])])

  ^  ^
  |  2 + 3(!) spaces
  2 spaces

3. Consecutive call / multi-line indentation

Consecutive calls to macros (= on the the same nesting level) are aligned vertically:

CALL([parameter],
  [CALL([])
   CALL([])
   CALL([])])

4. Closing bracket placement

Closing braces accumulate on the same line in general...

CALL(
  [CALL([CALL([])],
        [CALL([])])
   CALL([])])

...but can go a new line (e.g. with AC_LANG_SOURCE) to match parameter indentation rule (2), i.e. either

CALL([CALL([
    one
    two
  ])],
  [CALL()])

.. or ..

CALL([CALL([
        one
        two
     ])],
     [CALL()])