From 2821076981bfec80414c5e513383f06f1095d769 Mon Sep 17 00:00:00 2001
From: "Philip.Hazel" <Philip.Hazel@gmail.com>
Date: Sun, 23 Oct 2016 17:05:09 +0000
Subject: [PATCH] Diagnose an overall recursion (?0) inside a lookbehind as an
 error.

---
 ChangeLog            | 3 +++
 src/pcre2_compile.c  | 3 ++-
 testdata/testinput2  | 2 ++
 testdata/testoutput2 | 3 +++
 4 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 53d8afe..422245c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -96,6 +96,9 @@ only when PCRE2_NO_START_OPTIMIZE was *not* set:
 16. The "offset" modifier in pcre2test was not being ignored (as documented)
 when the POSIX API was in use.
 
+17. An overall recursion such as (?0) inside a lookbehind assertion was not 
+being diagnosed as an error.
+
 
 Version 10.22 29-July-2016
 --------------------------
diff --git a/src/pcre2_compile.c b/src/pcre2_compile.c
index ff4972a..8bb4251 100644
--- a/src/pcre2_compile.c
+++ b/src/pcre2_compile.c
@@ -8497,12 +8497,13 @@ for (;; pptr++)
       *errcodeptr = ERR15;  /* Non-existent subpattern */
       return -1;
       }
-
+    if (group == 0) goto ISNOTFIXED;  /* Local recursion */
     for (gptr = cb->parsed_pattern; *gptr != META_END; gptr++)
       {
       if (META_CODE(*gptr) == META_BIGVALUE) gptr++;
         else if (*gptr == (META_CAPTURE | group)) break;
       }
+     
     gptrend = parsed_skip(gptr, PSKIP_KET);
     if (pptr > gptr && pptr < gptrend) goto ISNOTFIXED;  /* Local recursion */
     for (r = recurses; r != NULL; r = r->prev) if (r->groupptr == gptr) break;
diff --git a/testdata/testinput2 b/testdata/testinput2
index 3a81dc0..ba7df01 100644
--- a/testdata/testinput2
+++ b/testdata/testinput2
@@ -4894,4 +4894,6 @@ a)"xI
 
 /(?=.*[A-Z])/I
 
+/()(?<=(?0))/
+
 # End of testinput2 
diff --git a/testdata/testoutput2 b/testdata/testoutput2
index ccdb5ef..697cab3 100644
--- a/testdata/testoutput2
+++ b/testdata/testoutput2
@@ -15338,6 +15338,9 @@ Capturing subpattern count = 0
 May match empty string
 Subject length lower bound = 0
 
+/()(?<=(?0))/
+Failed: error 125 at offset 2: lookbehind assertion is not fixed length
+
 # End of testinput2 
 Error -63: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data