xref: /third_party/libxml2/backport-regexp-Fix-cycle-check-in-xmlFAReduceEpsilonTransiti.patch

From 9f7b114232904a7d0e304bff30ed4b255f34a572 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Thu, 9 Mar 2023 05:25:09 +0100
Subject: [PATCH] regexp: Fix cycle check in xmlFAReduceEpsilonTransitions

The visited flag must only be reset after the first call to
xmlFAReduceEpsilonTransitions has finished. Visiting states multiple
times could lead to unnecessary processing of duplicate transitions.

Similar to 68eadabd.

Reference:https://github.com/GNOME/libxml2/commit/9f7b114232904a7d0e304bff30ed4b255f34a572
Conflict:NA

---
 xmlregexp.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/xmlregexp.c b/xmlregexp.c
index cc4ae6f..24f9fc0 100644
--- a/xmlregexp.c
+++ b/xmlregexp.c
@@ -1880,7 +1880,32 @@ xmlFAReduceEpsilonTransitions(xmlRegParserCtxtPtr ctxt, int fromnr,
 	    }
 	}
     }
+}
+
+/**
+ * xmlFAFinishReduceEpsilonTransitions:
+ * @ctxt:  a regexp parser context
+ * @fromnr:  the from state
+ * @tonr:  the to state
+ * @counter:  should that transition be associated to a counted
+ *
+ */
+static void
+xmlFAFinishReduceEpsilonTransitions(xmlRegParserCtxtPtr ctxt, int tonr) {
+    int transnr;
+    xmlRegStatePtr to;
+
+    to = ctxt->states[tonr];
+    if ((to->mark == XML_REGEXP_MARK_START) ||
+	(to->mark == XML_REGEXP_MARK_NORMAL))
+	return;
+
     to->mark = XML_REGEXP_MARK_NORMAL;
+    for (transnr = 0;transnr < to->nbTrans;transnr++) {
+	xmlRegTransPtr t1 = &to->trans[transnr];
+	if ((t1->to >= 0) && (t1->atom == NULL))
+            xmlFAFinishReduceEpsilonTransitions(ctxt, t1->to);
+    }
 }
 
 /**
@@ -2032,6 +2057,7 @@ xmlFAEliminateEpsilonTransitions(xmlRegParserCtxtPtr ctxt) {
 		    state->mark = XML_REGEXP_MARK_START;
 		    xmlFAReduceEpsilonTransitions(ctxt, statenr,
 				      newto, state->trans[transnr].counter);
+		    xmlFAFinishReduceEpsilonTransitions(ctxt, newto);
 		    state->mark = XML_REGEXP_MARK_NORMAL;
 #ifdef DEBUG_REGEXP_GRAPH
 		} else {
-- 
2.27.0