In the Fine Manual: @node Coding Style @section Coding Style In order to highlight the recommended coding style, here is a macro written the old way: @example dnl Check for EMX on OS/2. dnl _AC_EMXOS2 AC_DEFUN(_AC_EMXOS2, ... and the new way: @example # _AC_EMXOS2 # ---------- # Check for EMX on OS/2. m4_define([_AC_EMXOS2], Why the change AC_DEFUN -> m4_define ? "Macro Definitions" says: Autoconf macros are defined using the `AC_DEFUN' macro, which is similar to the M4 builtin `m4_define' macro. In addition to defining a macro, `AC_DEFUN' adds to it some code that is used to constrain the order in which macros are called (*note Prerequisite Macros::). An Autoconf macro definition looks like this: AC_DEFUN(MACRO-NAME, MACRO-BODY) and again the example shows: m4_define([AC_MSG_ERROR], rather than AC_DEFUN. So, what is considered good style? Cheers, Patrick