From c2b0a184a9e052d445bedda817b233c05424062e Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Wed, 25 Sep 2019 13:57:42 +0200
Subject: [PATCH] Fix empty branch in regex

Fixes bug 649244:
https://bugzilla.gnome.org/show_bug.cgi?id=649244

Closes #57.
---
 result/regexp/bug649244 |  9 +++++++++
 test/regexp/bug649244   |  9 +++++++++
 xmlregexp.c             | 14 +++++++-------
 3 files changed, 25 insertions(+), 7 deletions(-)
 create mode 100644 result/regexp/bug649244
 create mode 100644 test/regexp/bug649244

diff --git a/result/regexp/bug649244 b/result/regexp/bug649244
new file mode 100644
index 00000000..886ca2c8
--- /dev/null
+++ b/result/regexp/bug649244
@@ -0,0 +1,9 @@
+Regexp: S(a|)E
+SE: Ok
+SxE: Fail
+Regexp: S(|b)E
+SE: Ok
+SxE: Fail
+Regexp: S(a||b)E
+SE: Ok
+SxE: Fail
diff --git a/test/regexp/bug649244 b/test/regexp/bug649244
new file mode 100644
index 00000000..42988643
--- /dev/null
+++ b/test/regexp/bug649244
@@ -0,0 +1,9 @@
+=>S(a|)E
+SE
+SxE
+=>S(|b)E
+SE
+SxE
+=>S(a||b)E
+SE
+SxE
diff --git a/xmlregexp.c b/xmlregexp.c
index 10969177..7d4f63ee 100644
--- a/xmlregexp.c
+++ b/xmlregexp.c
@@ -5358,9 +5358,12 @@ xmlFAParseBranch(xmlRegParserCtxtPtr ctxt, xmlRegStatePtr to) {
 
     previous = ctxt->state;
     ret = xmlFAParsePiece(ctxt);
-    if (ret != 0) {
+    if (ret == 0) {
+        /* Empty branch */
+	xmlFAGenerateEpsilonTransition(ctxt, previous, to);
+    } else {
 	if (xmlFAGenerateTransitions(ctxt, previous,
-	        (CUR=='|' || CUR==')') ? to : NULL, ctxt->atom) < 0)
+	        (CUR=='|' || CUR==')' || CUR==0) ? to : NULL, ctxt->atom) < 0)
 	    return(-1);
 	previous = ctxt->state;
 	ctxt->atom = NULL;
@@ -5369,7 +5372,8 @@ xmlFAParseBranch(xmlRegParserCtxtPtr ctxt, xmlRegStatePtr to) {
 	ret = xmlFAParsePiece(ctxt);
 	if (ret != 0) {
 	    if (xmlFAGenerateTransitions(ctxt, previous,
-	            (CUR=='|' || CUR==')') ? to : NULL, ctxt->atom) < 0)
+	            (CUR=='|' || CUR==')' || CUR==0) ? to : NULL,
+                    ctxt->atom) < 0)
 		    return(-1);
 	    previous = ctxt->state;
 	    ctxt->atom = NULL;
@@ -5406,10 +5410,6 @@ xmlFAParseRegExp(xmlRegParserCtxtPtr ctxt, int top) {
     end = ctxt->state;
     while ((CUR == '|') && (ctxt->error == 0)) {
 	NEXT;
-	if (CUR == 0) {
-	    ERROR("expecting a branch after |")
-	    return;
-	}
 	ctxt->state = start;
 	ctxt->end = NULL;
 	xmlFAParseBranch(ctxt, end);