Make SubStringStub more robust wrt unsafe arguments.

test/cctest/test-strings.cc

Index: test/cctest/test-strings.cc
diff --git a/test/cctest/test-strings.cc b/test/cctest/test-strings.cc
index e2a179f9324d2375da2ee5a78ac9378f83086aee..8c4442c432246f1e0f3e8a1306b8bfbe0a4875aa 100644
--- a/test/cctest/test-strings.cc
+++ b/test/cctest/test-strings.cc
@@ -620,3 +620,16 @@ TEST(AsciiArrayJoin) {
   CHECK(result.IsEmpty());
   CHECK(context->HasOutOfMemoryException());
 }
+
+
+TEST(RobustSubStringStub) {
+  // This tests whether the SubStringStub can handle unsafe arguments.
+  // If not recognized, those unsafe arguments lead to out-of-bounds reads.
+  FLAG_allow_natives_syntax = true;
+  InitializeVM();
+  HandleScope scope;
+  v8::Local<v8::Value> result;
+  Handle<String> string;
+  CompileRun("%_SubString('abcdef', 0, 10000)");
+  CompileRun("%_SubString('abcdef', 5, 2)");

[Erik Corry, 2012/04/17 09:06:58]

I'd like more tests here.  Negative numbers, borderline numbers, heap numbers,
input strings large enough to trigger the creation of SlicedStrings, slices of
slices where the args are out of bounds for the slice, but not for the
underlying string.

+}