From b2294373d773d13f526e5eddcdce59ac582be3ba Mon Sep 17 00:00:00 2001
From: "Philip.Hazel" <Philip.Hazel@gmail.com>
Date: Mon, 2 Jul 2018 11:23:45 +0000
Subject: [PATCH] Ignore qualifiers on lookaheads within lookbehinds when
 checking for a fixed length.

---
 ChangeLog            |  4 ++++
 src/pcre2_compile.c  | 26 ++++++++++++++++++++++++++
 testdata/testinput1  | 10 ++++++++++
 testdata/testinput2  |  2 ++
 testdata/testoutput1 | 10 ++++++++++
 testdata/testoutput2 | 14 ++++++++++++++
 6 files changed, 66 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 5ee7cae..9e497ea 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -100,6 +100,10 @@ a pattern. Because \G is in a lookbehind assertion, there has to be a
 "bumpalong" before there can be a match. The automatic "advance by one 
 character after an empty string match" rule is therefore inappropriate. A more 
 complicated algorithm has now been implemented.
+
+22. When checking to see if a lookbehind is of fixed length, lookaheads were 
+correctly ignored, but qualifiers on lookaheads were not being ignored, leading 
+to an incorrect "lookbehind assertion is not fixed length" error.
       
 
 Version 10.31 12-February-2018
diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index 0f75f36..5a47f1d 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -8572,6 +8572,32 @@ for (;; pptr++)
     case META_LOOKAHEADNOT:
     pptr = parsed_skip(pptr + 1, PSKIP_KET);
     if (pptr == NULL) goto PARSED_SKIP_FAILED;
+    
+    /* Also ignore any qualifiers that follow a lookahead assertion. */
+    
+    switch (pptr[1])
+      {
+      case META_ASTERISK:
+      case META_ASTERISK_PLUS:
+      case META_ASTERISK_QUERY:   
+      case META_PLUS:
+      case META_PLUS_PLUS: 
+      case META_PLUS_QUERY:
+      case META_QUERY:
+      case META_QUERY_PLUS:
+      case META_QUERY_QUERY:       
+      pptr++;
+      break;
+      
+      case META_MINMAX:
+      case META_MINMAX_PLUS:
+      case META_MINMAX_QUERY:
+      pptr += 3;
+      break;
+      
+      default:
+      break;      
+      }
     break;
 
     /* Lookbehinds can be ignored, but must themselves be checked. */
diff --git a/testdata/testinput1 b/testdata/testinput1
index fb50238..1b3191c 100644
--- a/testdata/testinput1
+++ b/testdata/testinput1
@@ -6192,4 +6192,14 @@ ef) x/x,mark
 /(?<=\G.)/g,aftertext
     abc
 
+/(?<=(?=.)?)/
+
+/(?<=(?=.)?+)/
+
+/(?<=(?=.)*)/
+
+/(?<=(?=.){4,5})/
+
+/(?<=(?=.){4,5}x)/
+
 # End of testinput1 
diff --git a/testdata/testinput2 b/testdata/testinput2
index 7e703d5..cc4b59b 100644
--- a/testdata/testinput2
+++ b/testdata/testinput2
@@ -5435,4 +5435,6 @@ a)"xI
 
 /(?=a+)a(a+)++b/B
 
+/(?<=(?=.){4,5}x)/B
+
 # End of testinput2
diff --git a/testdata/testoutput1 b/testdata/testoutput1
index 348dcbc..06469fa 100644
--- a/testdata/testoutput1
+++ b/testdata/testoutput1
@@ -9831,4 +9831,14 @@ No match
  0: 
  0+ 
 
+/(?<=(?=.)?)/
+
+/(?<=(?=.)?+)/
+
+/(?<=(?=.)*)/
+
+/(?<=(?=.){4,5})/
+
+/(?<=(?=.){4,5}x)/
+
 # End of testinput1 
diff --git a/testdata/testoutput2 b/testdata/testoutput2
index 9f504f6..aab0c94 100644
--- a/testdata/testoutput2
+++ b/testdata/testoutput2
@@ -16583,6 +16583,20 @@ No match
         End
 ------------------------------------------------------------------
 
+/(?<=(?=.){4,5}x)/B
+------------------------------------------------------------------
+        Bra
+        AssertB
+        Reverse
+        Assert
+        Any
+        Ket
+        x
+        Ket
+        Ket
+        End
+------------------------------------------------------------------
+
 # End of testinput2
 Error -70: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data