[regexp, fuzzer] improve regexp fuzzer coverage.

test/fuzzer/regexp.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "include/v8.h"
 #include "src/factory.h"
 #include "src/objects-inl.h"
 #include "src/objects.h"
 #include "src/regexp/jsregexp.h"
 #include "test/fuzzer/fuzzer-support.h"
 
 namespace i = v8::internal;
 
+void Test(v8::Isolate* isolate, i::Handle<i::JSRegExp> regexp,
+          i::Handle<i::String> subject, i::Handle<i::JSArray> results_array) {
+  v8::TryCatch try_catch(isolate);
+  USE(i::RegExpImpl::Exec(regexp, subject, 0, results_array));
+}
+
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   v8_fuzzer::FuzzerSupport* support = v8_fuzzer::FuzzerSupport::Get();
   v8::Isolate* isolate = support->GetIsolate();
 
   v8::Isolate::Scope isolate_scope(isolate);
   v8::HandleScope handle_scope(isolate);
   v8::Context::Scope context_scope(support->GetContext());
   v8::TryCatch try_catch(isolate);
 
   i::FLAG_harmony_unicode_regexps = true;
   i::FLAG_harmony_regexp_lookbehind = true;
 
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   i::Factory* factory = i_isolate->factory();
 
   if (size > INT_MAX) return 0;
   i::MaybeHandle<i::String> maybe_source = factory->NewStringFromOneByte(
       i::Vector<const uint8_t>(data, static_cast<int>(size)));
   i::Handle<i::String> source;
   if (!maybe_source.ToHandle(&source)) return 0;
 
   static const int kAllFlags = i::JSRegExp::kGlobal | i::JSRegExp::kIgnoreCase |
                                i::JSRegExp::kMultiline | i::JSRegExp::kSticky |
                                i::JSRegExp::kUnicode;
 
   const uint8_t one_byte_array[6] = {'f', 'o', 'o', 'b', 'a', 'r'};
   const i::uc16 two_byte_array[6] = {'f', 0xD83D, 0xDCA9, 'b', 'a', 0x2603};
 
-  i::Handle<i::JSArray> results_array = factory->NewJSArray(4);
+  i::Handle<i::JSArray> results_array = factory->NewJSArray(5);
   i::Handle<i::String> one_byte =
       factory->NewStringFromOneByte(i::Vector<const uint8_t>(one_byte_array, 6))
           .ToHandleChecked();
   i::Handle<i::String> two_byte =
       factory->NewStringFromTwoByte(i::Vector<const i::uc16>(two_byte_array, 6))
           .ToHandleChecked();
 
   for (int flags = 0; flags <= kAllFlags; flags++) {
-    v8::TryCatch try_catch(isolate);
-    i::MaybeHandle<i::JSRegExp> maybe_regexp =
-        i::JSRegExp::New(source, static_cast<i::JSRegExp::Flags>(flags));
     i::Handle<i::JSRegExp> regexp;
-    if (!maybe_regexp.ToHandle(&regexp)) continue;
-    USE(i::RegExpImpl::Exec(regexp, one_byte, 0, results_array).is_null() &&
-        i::RegExpImpl::Exec(regexp, two_byte, 0, results_array).is_null());
+    {
+      v8::TryCatch try_catch(isolate);
+      i::MaybeHandle<i::JSRegExp> maybe_regexp =
+          i::JSRegExp::New(source, static_cast<i::JSRegExp::Flags>(flags));
+      if (!maybe_regexp.ToHandle(&regexp)) continue;
+    }
+    Test(isolate, regexp, one_byte, results_array);
+    Test(isolate, regexp, two_byte, results_array);
+    Test(isolate, regexp, factory->empty_string(), results_array);
+    Test(isolate, regexp, source, results_array);
   }
 
   return 0;
 }