From b5343d4a647d25640e16bfa1f813c39a7f2059a6 Mon Sep 17 00:00:00 2001
From: ph10 <ph10@6239d852-aaf2-0410-a92c-79f79f948069>
Date: Tue, 12 Dec 2017 15:01:51 +0000
Subject: [PATCH] Fix incorrect first matching character when a backreference
 with zero minimum repeat starts a pattern (possibly after assertions).
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git-svn-id: svn://vcs.exim.org/pcre2/code/trunk@888 6239d852-aaf2-0410-a92c-79f79f948069

Petr Písař: Ported to 10.30.
---
 src/pcre2_compile.c  |  2 +-
 testdata/testinput2  | 10 ++++++++++
 testdata/testoutput2 | 28 ++++++++++++++++++++++++++++

diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index 0b91d14..ad17338 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -7135,7 +7135,7 @@ for (;; pptr++)
     later. */
 
     HANDLE_SINGLE_REFERENCE:
-    if (firstcuflags == REQ_UNSET) firstcuflags = REQ_NONE;
+    if (firstcuflags == REQ_UNSET) zerofirstcuflags = firstcuflags = REQ_NONE;
     *code++ = ((options & PCRE2_CASELESS) != 0)? OP_REFI : OP_REF;
     PUT2INC(code, 0, meta_arg);
 
diff --git a/testdata/testinput2 b/testdata/testinput2
index 022df20..695f0a4 100644
--- a/testdata/testinput2
+++ b/testdata/testinput2
@@ -5375,4 +5375,14 @@ a)"xI
 
 /[\d-[:print:]]/
 
+# Perl gets the second of these wrong, giving no match.
+
+"(?<=(a))\1?b"I
+    ab
+    aaab 
+
+"(?=(a))\1?b"I
+    ab
+    aaab 
+
 # End of testinput2
diff --git a/testdata/testoutput2 b/testdata/testoutput2
index 2d9e347..31ccfbe 100644
--- a/testdata/testoutput2
+++ b/testdata/testoutput2
@@ -16340,6 +16340,34 @@ Failed: error 150 at offset 3: invalid range in character class
 /[\d-[:print:]]/
 Failed: error 150 at offset 3: invalid range in character class
 
+# Perl gets the second of these wrong, giving no match.
+
+"(?<=(a))\1?b"I
+Capturing subpattern count = 1
+Max back reference = 1
+Max lookbehind = 1
+Last code unit = 'b'
+Subject length lower bound = 1
+    ab
+ 0: b
+ 1: a
+    aaab 
+ 0: ab
+ 1: a
+
+"(?=(a))\1?b"I
+Capturing subpattern count = 1
+Max back reference = 1
+Starting code units: a 
+Last code unit = 'b'
+Subject length lower bound = 1
+    ab
+ 0: ab
+ 1: a
+    aaab 
+ 0: ab
+ 1: a
+
 # End of testinput2
 Error -65: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data
-- 
2.13.6