Fix bugs for patterns with conditional groups starting with assertions.

ChangeLog

@@ -72,6 +72,11 @@ branch and must therefore be treated as potentially matching an empty string.
 19. If (?R was followed by - or + incorrect behaviour happened instead of a
 diagnostic. This bug was discovered by Karl Skomski with the LLVM fuzzer.
 
+20. Another bug that was introduced by change 36 for 10.20: conditional groups 
+whose condition was an assertion preceded by an explicit callout with a string 
+argument might be incorrectly processed, especially if the string contained \Q.
+This bug was discovered by Karl Skomski with the LLVM fuzzer.
+
 
 Version 10.20 30-June-2015
 --------------------------

src/pcre2_compile.c

@@ -3323,10 +3323,39 @@ for (; ptr < cb->end_pattern; ptr++)
         goto FAILED;
         }
       break;
+      
+      /* Conditional group */
 
       case CHAR_LEFT_PARENTHESIS:
-      nest_depth++;
+      if (ptr[3] != CHAR_QUESTION_MARK)   /* Not assertion or callout */
-      /* Fall through */
+        {  
+        nest_depth++;
+        ptr += 2;
+        break; 
+        }
+        
+      /* Must be an assertion or a callout */
+ 
+      switch(ptr[4])
+       {
+       case CHAR_LESS_THAN_SIGN:
+       if (ptr[5] != CHAR_EXCLAMATION_MARK && ptr[5] != CHAR_EQUALS_SIGN) 
+         goto MISSING_ASSERTION;
+       /* Fall through */       
+
+       case CHAR_C:
+       case CHAR_EXCLAMATION_MARK:
+       case CHAR_EQUALS_SIGN:
+       ptr++;
+       break;
+       
+       default:
+       MISSING_ASSERTION: 
+       ptr += 3;            /* To improve error message */         
+       errorcode = ERR28;
+       goto FAILED; 
+       }      
+      break;
 
       case CHAR_COLON:
       case CHAR_GREATER_THAN_SIGN:

src/pcre2_error.c

@@ -92,7 +92,7 @@ static const char compile_error_texts[] =
   "failed to allocate heap memory\0"
   "unmatched closing parenthesis\0"
   "internal error: code overflow\0"
-  "unrecognized character after (?<\0"
+  "letter or underscore expected after (?< or (?'\0"
   /* 25 */
   "lookbehind assertion is not fixed length\0"
   "malformed number or name after (?(\0"

testdata/testinput2

@@ -4356,4 +4356,8 @@ a random value. /Ix
 
 /(?R-:(?</
 
+/(?(?C{\Q})(?!(?'/
+
+/(?(?C{\Q})(?!(?'abc')))/I
+
 # End of testinput2 

testdata/testoutput2

@@ -940,7 +940,7 @@ Failed: error 122 at offset 0: unmatched closing parenthesis
 Failed: error 114 at offset 4: missing closing parenthesis
 
 /(?<%)b/
-Failed: error 124 at offset 3: unrecognized character after (?<
+Failed: error 124 at offset 3: letter or underscore expected after (?< or (?'
 
 /a(?{)b/
 Failed: error 111 at offset 3: unrecognized character after (? or (?-
@@ -14488,16 +14488,16 @@ Failed: error 161 at offset 32: number is too big
 ------------------------------------------------------------------
 
 /[[:>:]](?<)/
-Failed: error 124 at offset 10: unrecognized character after (?<
+Failed: error 124 at offset 10: letter or underscore expected after (?< or (?'
 
 /((?x)(*:0))#(?'/
-Failed: error 124 at offset 15: unrecognized character after (?<
+Failed: error 124 at offset 15: letter or underscore expected after (?< or (?'
 
 /(?C$[$)(?<]/
-Failed: error 124 at offset 10: unrecognized character after (?<
+Failed: error 124 at offset 10: letter or underscore expected after (?< or (?'
 
 /(?C$)$)(?<]/
-Failed: error 124 at offset 10: unrecognized character after (?<
+Failed: error 124 at offset 10: letter or underscore expected after (?< or (?'
 
 /(?(R))*+/B
 ------------------------------------------------------------------
@@ -14515,7 +14515,7 @@ Failed: error 124 at offset 10: unrecognized character after (?<
  0: 
 
 /((?x)(?#))#(?'/
-Failed: error 124 at offset 14: unrecognized character after (?<
+Failed: error 124 at offset 14: letter or underscore expected after (?< or (?'
 
 /((?x)(?#))#(?'abc')/I
 Capturing subpattern count = 2
@@ -14525,7 +14525,7 @@ First code unit = '#'
 Subject length lower bound = 1
 
 /[[:\\](?<[::]/
-Failed: error 124 at offset 9: unrecognized character after (?<
+Failed: error 124 at offset 9: letter or underscore expected after (?< or (?'
 
 /[[:\\](?'abc')[a:]/I
 Capturing subpattern count = 1
@@ -14556,4 +14556,14 @@ Failed: error 106 at offset 353: missing terminating ] for character class
 /(?R-:(?</
 Failed: error 129 at offset 3: (?R or (?[+-]digits must be followed by )
 
+/(?(?C{\Q})(?!(?'/
+Failed: error 124 at offset 16: letter or underscore expected after (?< or (?'
+
+/(?(?C{\Q})(?!(?'abc')))/I
+Capturing subpattern count = 1
+Named capturing subpatterns:
+  abc   1
+May match empty string
+Subject length lower bound = 0
+
 # End of testinput2 

testdata/testoutput5

@@ -4051,6 +4051,6 @@ Failed: error 122 at offset 1227: unmatched closing parenthesis
 /$(&.+[\p{Me}].\s\xdcC*?(?(<y>))(?<!^)$C((;*?(R))+(?(R)){0,6}?|){12\x8a\X*?\x8a\x0b\xd1^9\3*+(\xc1,\k'P'\xb4)\xcc(z\z(?JJ)(?'X'8};(\x0b\xd1^9\?'3*+(\xc1.]k+\x0b'Pm'\xb4\xcc4'\xd1'(?'X'))?-%--\x95$9*\4'|\xd1(''%\x95*$9)#(?'R')3\x07?('P\xed')\\x16:;()\x1e\x10*:(?<y>)\xd1+!~:(?)''(d'E:yD!\s(?'R'\x1e;\x10:U))|')g!\xb0*){29+))#(?'P'})*?/
 
 "(*UTF)(*UCP)(.UTF).+X(\V+;\^(\D|)!999}(?(?C{7(?C')\H*\S*/^\x5\xa\\xd3\x85n?(;\D*(?m).[^mH+((*UCP)(*U:F)})(?!^)(?'"
-Failed: error 139 at offset 113: closing parenthesis for (?C expected
+Failed: error 124 at offset 113: letter or underscore expected after (?< or (?'
 
 # End of testinput5