Add missing integer overflow checks.

ChangeLog

@@ -98,6 +98,10 @@ minimum matching length gave a wrong result, which could cause incorrect "no
 match" errors. For such patterns, a minimum matching length cannot at present 
 be computed.
 
+26. Added a check for integer overflow in conditions (?(<digits>) and 
+(?(R<digits>). This omission was discovered by Karl Skomski with the LLVM
+fuzzer.
+
 
 Version 10.20 30-June-2015
 --------------------------

src/pcre2_compile.c

@@ -5954,6 +5954,12 @@ for (;; ptr++)
           {
           while (IS_DIGIT(*ptr))
             {
+            if (recno > INT_MAX / 10 - 1)  /* Integer overflow */
+              {
+              while (IS_DIGIT(*ptr)) ptr++;
+              *errorcodeptr = ERR61;
+              goto FAILED;   
+              }   
             recno = recno * 10 + (int)(*ptr - CHAR_0);
             ptr++;
             }
@@ -6089,7 +6095,12 @@ for (;; ptr++)
             {
             if (!IS_DIGIT(name[i]))
               {
-              *errorcodeptr = ERR15;
+              *errorcodeptr = ERR15;        /* Non-existent subpattern */
+              goto FAILED;
+              }
+            if (recno > INT_MAX / 10 - 1)   /* Integer overflow */
+              {
+              *errorcodeptr = ERR61;
               goto FAILED;   
               }     
             recno = recno * 10 + name[i] - CHAR_0;

testdata/testinput2

@@ -4408,4 +4408,8 @@ a random value. /Ix
 /.*?a(*SKIP)b/
     aab
 
+/(?(8000000000/
+
+/((?(R8000000000)))/
+
 # End of testinput2 

testdata/testoutput2

@@ -14661,4 +14661,10 @@ No match
     aab
  0: ab
 
+/(?(8000000000/
+Failed: error 161 at offset 13: number is too big
+
+/((?(R8000000000)))/
+Failed: error 161 at offset 16: number is too big
+
 # End of testinput2