Make mojo buffer allocators more robust.

mojo/public/cpp/bindings/tests/buffer_unittest.cc

 // Copyright 2014 The Chromium 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 <limits>
 
 #include "mojo/public/cpp/bindings/buffer.h"
 #include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
 #include "mojo/public/cpp/bindings/lib/fixed_buffer.h"
 #include "mojo/public/cpp/bindings/lib/scratch_buffer.h"
@@ skipping 25 matching lines @@
 
   // Large allocations won't be on the stack.
   void* large = buf.Allocate(100*1024);
   EXPECT_TRUE(IsZero(large, 100*1024));
   EXPECT_FALSE(large >= &buf && large < (&buf + sizeof(buf)));
 
   // But another small allocation should be back on the stack.
   small = buf.Allocate(10);
   EXPECT_TRUE(IsZero(small, 10));
   EXPECT_TRUE(small >= &buf && small < (&buf + sizeof(buf)));
+
+  // And a request so large it will fail.
+  void* fail = buf.Allocate(std::numeric_limits<size_t>::max() - 1024u);
+  EXPECT_TRUE(!fail);
+
+  // And a request so large it will overflow and fail.
+  void* overflow = buf.Allocate(std::numeric_limits<size_t>::max() - 12u);
+  EXPECT_TRUE(!overflow);
 }
 
 // Tests that Buffer::current() returns the correct value.
 TEST(ScratchBufferTest, Stacked) {
   Environment env;
 
   EXPECT_FALSE(Buffer::current());
 
   {
     internal::ScratchBuffer a;
@@ skipping 62 matching lines @@
   Environment env;
 
   internal::FixedBuffer buf(24);
 
   // A little bit too large.
   EXPECT_EQ(reinterpret_cast<void*>(0), buf.Allocate(32));
 
   // Move the cursor forward.
   EXPECT_NE(reinterpret_cast<void*>(0), buf.Allocate(16));
 
+  // A lot too large.
+  EXPECT_EQ(reinterpret_cast<void*>(0),
+            buf.Allocate(std::numeric_limits<size_t>::max() - 1024u));
+
   // A lot too large, leading to possible integer overflow.
   EXPECT_EQ(reinterpret_cast<void*>(0),
             buf.Allocate(std::numeric_limits<size_t>::max() - 8u));
 }
 #endif
 
 }  // namespace
 }  // namespace test
 }  // namespace mojo