Fix bad lookbehind compilation when preceded by a DEFINE group.

ChangeLog

@@ -77,6 +77,11 @@ low surrogate. This caused incorrect behaviour, for example when
 PCRE2_MATCH_INVALID_UTF was set and a match started immediately following the
 invalid high surrogate, such as /aa/ matching "\x{d800}aa".
 
+20. If a DEFINE group immediately preceded a lookbehind assertion, the pattern 
+could be mis-compiled and therefore not match correctly. This is the example 
+that found this: /(?(DEFINE)(?<foo>bar))(?<![-a-z0-9])word/ which failed to 
+match "word" because the "move back" value was set to zero.
+
 
 Version 10.34 21-November-2019
 ------------------------------

src/pcre2_compile.c

@@ -8019,6 +8019,7 @@ and skip over the pattern offset. */
 lookbehind = *code == OP_ASSERTBACK ||
              *code == OP_ASSERTBACK_NOT ||
              *code == OP_ASSERTBACK_NA;
+
 if (lookbehind)
   {
   lookbehindlength = META_DATA(pptr[-1]);
@@ -9553,6 +9554,10 @@ for (; *pptr != META_END; pptr++)
     break;
 
     case META_COND_DEFINE:
+    pptr += SIZEOFFSET;
+    nestlevel++;
+    break;
+
     case META_COND_NAME:
     case META_COND_NUMBER:
     case META_COND_RNAME:

testdata/testinput1

@@ -6424,4 +6424,7 @@ ef) x/x,mark
 "(?<=X(?(DEFINE)(Y))(?1))."
     AXYZ
 
+"(?(DEFINE)(?<foo>bar))(?<![-a-z0-9])word"
+    word
+
 # End of testinput1 

testdata/testoutput1

@@ -10182,4 +10182,8 @@ No match
     AXYZ
  0: Z
 
+"(?(DEFINE)(?<foo>bar))(?<![-a-z0-9])word"
+    word
+ 0: word
+
 # End of testinput1