Let patsubst handle empty patterns: those match anywhere, and don't

replace any character.
Like gnu-m4 does, and other regexp languages do.

okay fries@

3 files changed, 29 insertions, 16 deletions

diff --git a/regress/usr.bin/m4/patterns.m4 b/regress/usr.bin/m4/patterns.m4
index 6aedcd25bdc..af37c2ba177 100644
--- a/regress/usr.bin/m4/patterns.m4
+++ b/regress/usr.bin/m4/patterns.m4
@@ -1,4 +1,4 @@
-dnl $OpenBSD: patterns.m4,v 1.3 2001/09/27 12:34:52 espie Exp $
+dnl $OpenBSD: patterns.m4,v 1.4 2003/06/08 20:11:45 espie Exp $
 patsubst(`quote s in string', `(s)', `\\\1')
 patsubst(`check whether subst
 over several lines
@@ -7,3 +7,5 @@ patsubst(`# This is a line to zap
 # and a second line
 keep this one', `^ *#.*
 ')
+dnl Special case: empty regexp
+patsubst(`empty regexp',`',`a ')
diff --git a/regress/usr.bin/m4/patterns.out b/regress/usr.bin/m4/patterns.out
index 9e33be7c2ea..c273b589d77 100644
--- a/regress/usr.bin/m4/patterns.out
+++ b/regress/usr.bin/m4/patterns.out
@@ -3,3 +3,4 @@ quote \s in \string
 >>>over several lines
 >>>works as expected
 keep this one
+a ea ma pa ta ya  a ra ea ga ea xa p
diff --git a/usr.bin/m4/gnum4.c b/usr.bin/m4/gnum4.c
index 6ca4d9a45cd..553ef38da1a 100644
--- a/usr.bin/m4/gnum4.c
+++ b/usr.bin/m4/gnum4.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: gnum4.c,v 1.19 2003/06/07 12:02:35 espie Exp $ */
+/* $OpenBSD: gnum4.c,v 1.20 2003/06/08 20:11:45 espie Exp $ */
 
 /*
  * Copyright (c) 1999 Marc Espie
@@ -429,25 +429,35 @@ twiddle(const char *p)
 void
 dopatsubst(const char *argv[], int argc)
 {
-	int error;
-	regex_t re;
-	regmatch_t *pmatch;
-
 	if (argc <= 3) {
 		warnx("Too few arguments to patsubst");
 		return;
 	}
-	error = regcomp(&re, mimic_gnu ? twiddle(argv[3]) : argv[3], 
-	    REG_NEWLINE | REG_EXTENDED);
-	if (error != 0)
-		exit_regerror(error, &re);
-	
-	pmatch = xalloc(sizeof(regmatch_t) * (re.re_nsub+1));
-	do_subst(argv[2], &re, 
-	    argc != 4 && argv[4] != NULL ? argv[4] : "", pmatch);
+	/* special case: empty regexp */
+	if (argv[3][0] == '\0') {
+		const char *s;
+		size_t len = strlen(argv[4]);
+		for (s = argv[2]; *s != '\0'; s++) {
+			addchars(argv[4], len);
+			addchar(*s);
+		}
+	} else {
+		int error;
+		regex_t re;
+		regmatch_t *pmatch;
+
+		error = regcomp(&re, mimic_gnu ? twiddle(argv[3]) : argv[3], 
+		    REG_NEWLINE | REG_EXTENDED);
+		if (error != 0)
+			exit_regerror(error, &re);
+		
+		pmatch = xalloc(sizeof(regmatch_t) * (re.re_nsub+1));
+		do_subst(argv[2], &re, 
+		    argc != 4 && argv[4] != NULL ? argv[4] : "", pmatch);
+		free(pmatch);
+		regfree(&re);
+	}
 	pbstr(getstring());
-	free(pmatch);
-	regfree(&re);
 }
 
 void