$NetBSD: patch-am,v 1.5 2010/08/26 20:05:28 cheusov Exp $

--- regexp_system.c.orig	2010-06-25 20:43:03.000000000 +0000
+++ regexp_system.c
@@ -286,7 +286,22 @@ prepare_regexp(char *regexp, const char 
 void *
 REcompile(char *regexp, size_t len)
 {
+    int ere_flags = REG_EXTENDED;
+#ifdef REG_ONESUB
+    ere_flags |= REG_ONESUB;
+#endif
+#ifdef REG_BKTEMPTY
+    ere_flags |= REG_BKTEMPTY;
+#endif
+#ifdef REG_BKTESCAPE
+    ere_flags |= REG_BKTESCAPE;
+#endif
+#ifdef REG_ESCSEQ
+    ere_flags |= REG_ESCSEQ;
+#endif
+
     mawk_re_t *re = (mawk_re_t *) malloc(sizeof(mawk_re_t));
+    char *new_regexp = (char *) malloc(len + 3);
 
     if (re != 0) {
 	size_t need = (len * 2) + 8;	/* might double, with escaping */
@@ -308,7 +323,7 @@ REcompile(char *regexp, size_t len)
 
 	    memset(re, 0, sizeof(mawk_re_t));
 	    re->regexp = strdup(new_regexp);
-	    err_code = regcomp(&re->re, new_regexp, REG_EXTENDED);
+	    err_code = regcomp(&re->re, new_regexp, ere_flags);
 
 	    free(new_regexp);