This script takes configuration fragments and generates full Bison grammar

from them.

conf/gen_parser.m4

@@ -0,0 +1,63 @@
+m4_divert(-1)m4_dnl
+#
+#	BIRD -- Generator of Configuration Grammar
+#
+#	(c) 1998 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
+#
+#	Can be freely distributed and used under the terms of the GNU GPL.
+#
+
+# Diversions used:
+#	1	includes
+#	2	types etc.
+#	3	rules
+#	4	C code
+
+# Common aliases
+m4_define(DNL, `m4_dnl')
+
+# Define macros for defining sections
+m4_define(CF_ZONE, `m4_divert($1)/* $2 from m4___file__ */')
+m4_define(CF_HDR, `CF_ZONE(1, Headers)')
+m4_define(CF_DECLS, `CF_ZONE(2, Declarations)')
+m4_define(CF_GRAMMAR, `CF_ZONE(3, Grammar)')
+m4_define(CF_CODE, `CF_ZONE(4, C Code)')
+m4_define(CF_END, `m4_divert(-1)')
+
+# Simple iterator
+m4_define(CF_itera, `m4_ifelse($#, 1, [[CF_iter($1)]], [[CF_iter($1)[[]]CF_itera(m4_shift($@))]])')
+m4_define(CF_iterate, `m4_define([[CF_iter]], m4_defn([[$1]]))CF_itera($2)')
+
+# Keywords act as untyped %token
+m4_define(CF_keywd, `m4_ifdef([[CF_tok_$1]],,[[m4_define([[CF_tok_$1]],1)m4_define([[CF_toks]],CF_toks $1)]])')
+m4_define(CF_KEYWORDS, `m4_define([[CF_toks]],[[]])CF_iterate([[CF_keywd]], [[$@]])m4_ifelse(CF_toks,,,%token[[]]CF_toks
+)DNL')
+
+# Dynamic syntax rules
+m4_define(CF_dyn_rules,)
+m4_define(CF_ADDTO, `m4_define([[CF_rule_$1]],m4_ifdef([[CF_rule_$1]],CF_rule_$1 | ,[[m4_define([[CF_dyn_rules]],CF_dyn_rules[[CF_RULE($1)
+]])]])$2)DNL')
+m4_define(CF_RULE, `$1: CF_rule_$1')
+
+# After all configuration templates end, we finally generate the grammar file.
+m4_m4wrap(`
+m4_divert(0)DNL
+%{
+m4_undivert(1)DNL
+%}
+
+m4_undivert(2)DNL
+
+%%
+m4_undivert(3)DNL
+
+/* Dynamic rules */
+
+CF_dyn_rules
+%%
+m4_undivert(4)DNL
+')
+
+# As we are processing C source, we must access all M4 primitives via
+# m4_* and also set different quoting convention: `[[' and ']]'
+m4_changequote([[,]])