From c2b0868c4d213b2599daf5fee4d1f957f153bc02 Mon Sep 17 00:00:00 2001
From: Hugo van der Sanden <hv@crypt.org>
Date: Thu, 7 Aug 2003 03:44:23 +0100
Subject: Re: [perl #23030] Error in negative lookahead with alternations
 Message-Id: <200308070144.h771iN906446@zen.crypt.org>

p4raw-id: //depot/perl@20538
---
 regexec.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

(limited to 'regexec.c')

diff --git a/regexec.c b/regexec.c
index df96924d89..11279337ea 100644
--- a/regexec.c
+++ b/regexec.c
@@ -87,6 +87,7 @@
 #define RF_warned	2		/* warned about big count? */
 #define RF_evaled	4		/* Did an EVAL with setting? */
 #define RF_utf8		8		/* String contains multibyte chars? */
+#define RF_false	16		/* odd number of nested negatives */
 
 #define UTF ((PL_reg_flags & RF_utf8) != 0)
 
@@ -3204,7 +3205,10 @@ S_regmatch(pTHX_ regnode *prog)
 				      "%*s  already tried at this position...\n",
 				      REPORT_CODE_OFF+PL_regindent*2, "")
 			);
-			sayNO_SILENT;
+			if (PL_reg_flags & RF_false)
+			    sayYES;
+			else
+			    sayNO_SILENT;
 		    }
 		    PL_reg_poscache[o] |= (1<<b);
 		}
@@ -3854,6 +3858,7 @@ S_regmatch(pTHX_ regnode *prog)
 	    }
 	    else
 		PL_reginput = locinput;
+	    PL_reg_flags ^= RF_false;
 	    goto do_ifmatch;
 	case IFMATCH:
 	    n = 1;
@@ -3869,6 +3874,8 @@ S_regmatch(pTHX_ regnode *prog)
 	  do_ifmatch:
 	    inner = NEXTOPER(NEXTOPER(scan));
 	    if (regmatch(inner) != n) {
+		if (n == 0)
+		    PL_reg_flags ^= RF_false;
 	      say_no:
 		if (logical) {
 		    logical = 0;
@@ -3878,6 +3885,8 @@ S_regmatch(pTHX_ regnode *prog)
 		else
 		    sayNO;
 	    }
+	    if (n == 0)
+		PL_reg_flags ^= RF_false;
 	  say_yes:
 	    if (logical) {
 		logical = 0;
-- 
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