Index: usr.bin/m4/m4.1
===================================================================
RCS file: /home/dcvs/src/usr.bin/m4/m4.1,v
retrieving revision 1.3
diff -u -r1.3 m4.1
--- usr.bin/m4/m4.1	27 Dec 2006 21:29:02 -0000	1.3
+++ usr.bin/m4/m4.1	28 Dec 2006 00:10:12 -0000
@@ -12,7 +12,7 @@
 .Nm
 .Op Fl d Ar flags
 .Op Fl t Ar name
-.Op Fl gs
+.Op Fl Pgs
 .Op Fl D Ar name Ns Op = Ns Ar value
 .Op Fl U Ar name
 .Op Fl I Ar dirname
@@ -69,6 +69,19 @@
 .It Fl U Ar name
 Undefine the symbol
 .Ar name .
+.It Fl P
+Prefixes all
+.Nm
+builtin macros with the string
+.Li m4_ .
+This changes the macro names
+.Li dnl
+to
+.Li m4_dnl ,
+.Li index
+to
+.Li m4_index ,
+and so forth.
 .It Fl I Ar dirname
 Add directory
 .Ar dirname
Index: usr.bin/m4/main.c
===================================================================
RCS file: /home/dcvs/src/usr.bin/m4/main.c,v
retrieving revision 1.3
diff -u -r1.3 main.c
--- usr.bin/m4/main.c	27 Dec 2006 21:29:02 -0000	1.3
+++ usr.bin/m4/main.c	28 Dec 2006 00:24:20 -0000
@@ -82,6 +82,7 @@
 int oindex = 0; 		/* diversion index..	       */
 char null[] = "";		/* as it says.. just a null..  */
 const char *m4wraps = "";       /* m4wrap string default..     */
+int m4prefix = 0;		/* prefix keywords with m4_    */
 char lquote[MAXCCHARS+1] = {LQUOTE};	/* left quote character  (`)   */
 char rquote[MAXCCHARS+1] = {RQUOTE};	/* right quote character (')   */
 char scommt[MAXCCHARS+1] = {SCOMMT};	/* start character for comment */
@@ -177,6 +178,14 @@
 	if (signal(SIGINT, SIG_IGN) != SIG_IGN)
 		signal(SIGINT, onintr);
 
+	/*
+	 * We need to know if -P is there before checking -D and -U.
+	 */
+	while ((c = getopt(argc, argv, "Pgst:d:D:U:o:I:")) != -1)
+		if (c == 'P')
+			m4prefix = 1;
+	optind = 1;
+
 	initkwds();
 	initspaces();
 	STACKMAX = INITSTACKMAX;
@@ -188,7 +197,7 @@
 	outfile = NULL;
 	resizedivs(MAXOUT);
 
-	while ((c = getopt(argc, argv, "gst:d:D:U:o:I:")) != -1)
+	while ((c = getopt(argc, argv, "Pgst:d:D:U:o:I:")) != -1)
 		switch(c) {
 		case 'D':               /* define something..*/
 			for (p = optarg; *p; p++)
@@ -203,6 +212,8 @@
 		case 'I':
 			addtoincludepath(optarg);
 			break;
+		case 'P':
+			break;
 		case 'U':               /* undefine...       */
 			remhash(optarg, TOP);
 			break;
@@ -563,9 +574,16 @@
 	size_t i;
 	unsigned int h;
 	ndptr p;
+	char *k;
 
 	for (i = 0; i < MAXKEYS; i++) {
-		h = hash(keywrds[i].knam);
+		k = (char *)keywrds[i].knam;
+		if (m4prefix) {
+			if (asprintf(&k, "m4_%s", k) == -1)
+				err(1, "asprintf");
+			keywrds[i].knam = k;
+		}
+		h = hash(k);
 		p = (ndptr) xalloc(sizeof(struct ndblock));
 		p->nxtptr = hashtab[h % HASHSIZE];
 		hashtab[h % HASHSIZE] = p;