[wasm] Verify boundaries of data segments when decoding modules.

src/wasm/wasm-opcodes.cc

Index: src/wasm/wasm-opcodes.cc
diff --git a/src/wasm/wasm-opcodes.cc b/src/wasm/wasm-opcodes.cc
index 25eef034d7f3e7b86d6d9c78d52b14fdc83c38c9..a609e032611ce8633ee5c148882dfb0df9503e50 100644
--- a/src/wasm/wasm-opcodes.cc
+++ b/src/wasm/wasm-opcodes.cc
@@ -25,6 +25,20 @@ const char* WasmOpcodes::OpcodeName(WasmOpcode opcode) {
 }
 
 
+std::ostream& operator<<(std::ostream& os, const FunctionSig& sig) {
+  if (sig.return_count() == 0) os << "v";
+  for (size_t i = 0; i < sig.return_count(); i++) {
+    os << WasmOpcodes::ShortNameOf(sig.GetReturn(i));
+  }
+  os << "_";
+  if (sig.parameter_count() == 0) os << "v";
+  for (size_t i = 0; i < sig.parameter_count(); i++) {
+    os << WasmOpcodes::ShortNameOf(sig.GetParam(i));
+  }
+  return os;
+}
+
+
 #define DECLARE_SIG_ENUM(name, ...) kSigEnum_##name,