[asmjs] Validator should reject modules with repeated functions.

R=ahaas@chromium.org,aseemgarg@chromium.org,bradnelson@chromium.org
BUG=chromium:617525

Review-Url: https://codereview.chromium.org/2040983002
Cr-Commit-Position: refs/heads/master@{#36748}

src/typing-asm.cc

@@ -166,6 +166,10 @@ void AsmTyper::VisitFunctionDeclaration(FunctionDeclaration* decl) {
   // Set function type so global references to functions have some type
   // (so they can give a more useful error).
   Variable* var = decl->proxy()->var();
+  if (GetVariableInfo(var)) {
+    // Detect previously-seen functions.
+    FAIL(decl->fun(), "function repeated in module");
+  }
   SetType(var, Type::Function());
 }
 

test/cctest/test-asm-validator.cc

@@ -1361,6 +1361,12 @@ TEST(CompareMismatchInt32Float32) {
       "asm: line 1: left and right side of comparison must match\n");
 }
 
+TEST(FunctionRepeated) {
+  CHECK_FUNC_ERROR(
+      "function foo() { return 0; }\n"
+      "function foo() { return 0; }",
+      "asm: line 2: function repeated in module\n");
+}
 
 TEST(Float64ToInt32) {
   CHECK_FUNC_TYPES_BEGIN(

test/mjsunit/regress/regress-617525.js

+// 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.
+
+function __f_14() {
+  "use asm";
+  function __f_15() { return 0; }
+  function __f_15() { return 137; }  // redeclared function
+  return {};
+}
+assertThrows(function() { Wasm.instantiateModuleFromAsm(__f_14.toString()) });