--- a/usr/src/cmd/sgs/m4/common/m4.c	Wed Apr 27 02:07:11 2011 +0000
+++ b/usr/src/cmd/sgs/m4/common/m4.c	Fri May 06 07:32:53 2011 -0700
@@ -23,6 +23,10 @@
  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
  */
 
+/*
+ * Copyright (c) 2011 Gary Mills
+ */
+
 /*	Copyright (c) 1988 AT&T	*/
 /*	  All Rights Reserved  	*/
 
@@ -805,7 +809,8 @@
 	FILE	*fp;
 
 	if ((fp = fopen(name, mode)) == NULL)
-		error(gettext("can't open file"));
+		errorf(gettext("cannot open file: %s"),
+		    strerror(errno));
 
 	return (fp);
 }
@@ -865,6 +870,17 @@
 	return (ptr);
 }
 
+/* Typical format: "cannot open file: %s" */
+/* PRINTFLIKE1 */
+void
+errorf(char *str, char *serr)
+{
+	char buf[500];
+
+	(void) snprintf(buf, sizeof (buf), str, serr);
+	error(buf);
+}
+
 /* PRINTFLIKE1 */
 void
 error2(char *str, int num)

--- a/usr/src/cmd/sgs/m4/common/m4.h	Wed Apr 27 02:07:11 2011 +0000
+++ b/usr/src/cmd/sgs/m4/common/m4.h	Fri May 06 07:32:53 2011 -0700
@@ -26,6 +26,10 @@
  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
  */
 
+/*
+ * Copyright (c) 2011 Gary Mills
+ */
+
 #ifndef	_M4_H
 #define	_M4_H
 
@@ -33,6 +37,7 @@
 #include	<stdio.h>
 #include	<stdlib.h>
 #include	<string.h>
+#include	<errno.h>
 #include	<locale.h>
 #include	<limits.h>
 
@@ -161,6 +166,7 @@
 extern int min(int, int);
 extern void putbak(wchar_t);
 extern void stkchr(wchar_t);
+extern void errorf(char *, char *);
 extern void error2(char *, int);
 
 extern wchar_t *wstrdup(wchar_t *);

--- a/usr/src/cmd/sgs/m4/common/m4macs.c	Wed Apr 27 02:07:11 2011 +0000
+++ b/usr/src/cmd/sgs/m4/common/m4macs.c	Fri May 06 07:32:53 2011 -0700
@@ -24,11 +24,13 @@
  * Use is subject to license terms.
  */
 
+/*
+ * Copyright (c) 2011 Gary Mills
+ */
+
 /*	Copyright (c) 1988 AT&T	*/
 /*	  All Rights Reserved  	*/
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include	<limits.h>
 #include	<unistd.h>
 #include	<sys/types.h>
@@ -297,8 +299,8 @@
 		if ((ifile[++ifx] = fopen(wstr2str(ap[1], 0), "r")) == NULL) {
 			--ifx;
 			if (noisy)
-				error(gettext(
-				"can't open file"));
+				errorf(gettext("cannot open file: %s"),
+				    strerror(errno));
 		} else {
 			ipstk[ifx] = ipflr = ip;
 			setfname(wstr2str(ap[1], 0));