Fix bug in processing (?(DEFINE)...) within lookbehind assertions.

ChangeLog

@@ -48,6 +48,14 @@ the minimum.
 13. In pcre2grep, if the final line in a scanned file is output but does not 
 end with a newline sequence, add a newline according to the --newline setting.
 
+14. (?(DEFINE)...) groups were not being handled correctly when checking for 
+the fixed length of a lookbehind assertion. Such a group within a lookbehind 
+should be skipped, as it does not contribute to the length of the group. 
+Instead, the (DEFINE) group was being processed, and if at the end of the 
+lookbehind, that end was not correctly recognized. Errors such as "lookbehind 
+assertion is not fixed length" and also "internal error: bad code value in 
+parsed_skip()" could result.
+
 
 Version 10.34 21-November-2019
 ------------------------------

src/pcre2_compile.c

@@ -8800,9 +8800,10 @@ memset(slot + IMM2_SIZE + length, 0,
 
 /* This function is called to skip parts of the parsed pattern when finding the
 length of a lookbehind branch. It is called after (*ACCEPT) and (*FAIL) to find
-the end of the branch, it is called to skip over an internal lookaround, and it
-is also called to skip to the end of a class, during which it will never
-encounter nested groups (but there's no need to have special code for that).
+the end of the branch, it is called to skip over an internal lookaround or
+(DEFINE) group, and it is also called to skip to the end of a class, during
+which it will never encounter nested groups (but there's no need to have
+special code for that).
 
 When called to find the end of a branch or group, pptr must point to the first
 meta code inside the branch, not the branch-starting code. In other cases it
@@ -9280,14 +9281,21 @@ for (;; pptr++)
     itemlength = grouplength;
     break;
 
-    /* Check nested groups - advance past the initial data for each type and
-    then seek a fixed length with get_grouplength(). */
+    /* A (DEFINE) group is never obeyed inline and so it does not contribute to
+    the length of this branch. Skip from the following item to the next
+    unpaired ket. */
+
+    case META_COND_DEFINE:
+    pptr = parsed_skip(pptr + 1, PSKIP_KET);
+    break;
+
+    /* Check other nested groups - advance past the initial data for each type
+    and then seek a fixed length with get_grouplength(). */
 
     case META_COND_NAME:
     case META_COND_NUMBER:
     case META_COND_RNAME:
     case META_COND_RNUMBER:
-    case META_COND_DEFINE:
     pptr += 2 + SIZEOFFSET;
     goto CHECK_GROUP;
 

testdata/testinput1

@@ -6411,4 +6411,17 @@ ef) x/x,mark
     Hackdaws love my big sphinx of quartz.
     Pack my fox with five dozen liquor jugs.
 
+"(?<=X(?(DEFINE)(A)))X(*F)"
+\= Expect no match
+    AXYZ
+
+"(?<=X(?(DEFINE)(A)))."
+    AXYZ
+
+"(?<=X(?(DEFINE)(.*))Y)."
+    AXYZ
+
+"(?<=X(?(DEFINE)(Y))(?1))."
+    AXYZ
+
 # End of testinput1 

testdata/testinput2

@@ -5806,4 +5806,8 @@ a)"xI
     12abc34xyz99abc55\=substitute_skip=1
     12abc34xyz99abc55\=substitute_skip=2
 
+# Expect non-fixed-length error
+
+"(?<=X(?(DEFINE)(.*))(?1))."
+
 # End of testinput2

testdata/testoutput1

@@ -10165,4 +10165,21 @@ No match
     Pack my fox with five dozen liquor jugs.
 No match
 
+"(?<=X(?(DEFINE)(A)))X(*F)"
+\= Expect no match
+    AXYZ
+No match
+
+"(?<=X(?(DEFINE)(A)))."
+    AXYZ
+ 0: Y
+
+"(?<=X(?(DEFINE)(.*))Y)."
+    AXYZ
+ 0: Z
+
+"(?<=X(?(DEFINE)(Y))(?1))."
+    AXYZ
+ 0: Z
+
 # End of testinput1 

testdata/testoutput2

@@ -17536,6 +17536,11 @@ Callout 0: last capture = 2
  3(2) Old 12 15 "abc" New 5 10 "<abc>"
  3: <abc><abc>
 
+# Expect non-fixed-length error
+
+"(?<=X(?(DEFINE)(.*))(?1))."
+Failed: error 125 at offset 0: lookbehind assertion is not fixed length
+
 # End of testinput2
 Error -70: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data