Make FencedAlloctor fail on size = 0

BUG=none
R=piman@chromium.org


Review URL: https://chromiumcodereview.appspot.com/11419280

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171235 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 22 insertions, 3 deletions

diff --git a/gpu/command_buffer/client/fenced_allocator.cc b/gpu/command_buffer/client/fenced_allocator.cc
index d262115..0d395c4 100644
--- a/gpu/command_buffer/client/fenced_allocator.cc
+++ b/gpu/command_buffer/client/fenced_allocator.cc
@@ -39,9 +39,11 @@ FencedAllocator::~FencedAllocator() {
 // optimizing what to wait for, just looks inside the block in order (first-fit
 // as well).
 FencedAllocator::Offset FencedAllocator::Alloc(unsigned int size) {
-  // Similarly to malloc, an allocation of 0 allocates at least 1 byte, to
-  // return different pointers every time.
-  if (size == 0) size = 1;
+  // size of 0 is not allowed because it would be inconsistent to only sometimes
+  // have it succeed. Example: Alloc(SizeOfBuffer), Alloc(0).
+  if (size == 0)  {
+    return kInvalidOffset;
+  }
 
   // Try first to allocate in a free block.
   for (unsigned int i = 0; i < blocks_.size(); ++i) {
diff --git a/gpu/command_buffer/client/fenced_allocator_test.cc b/gpu/command_buffer/client/fenced_allocator_test.cc
index 381237b..44fb851 100644
--- a/gpu/command_buffer/client/fenced_allocator_test.cc
+++ b/gpu/command_buffer/client/fenced_allocator_test.cc
@@ -126,6 +126,14 @@ TEST_F(FencedAllocatorTest, TestBasic) {
   EXPECT_TRUE(allocator_->CheckConsistency());
 }
 
+// Test alloc 0 fails.
+TEST_F(FencedAllocatorTest, TestAllocZero) {
+  FencedAllocator::Offset offset = allocator_->Alloc(0);
+  EXPECT_EQ(FencedAllocator::kInvalidOffset, offset);
+  EXPECT_FALSE(allocator_->InUse());
+  EXPECT_TRUE(allocator_->CheckConsistency());
+}
+
 // Checks out-of-memory condition.
 TEST_F(FencedAllocatorTest, TestOutOfMemory) {
   EXPECT_TRUE(allocator_->CheckConsistency());
@@ -446,6 +454,15 @@ TEST_F(FencedAllocatorWrapperTest, TestBasic) {
   allocator_->Free(pointer_uint);
 }
 
+// Test alloc 0 fails.
+TEST_F(FencedAllocatorWrapperTest, TestAllocZero) {
+  allocator_->CheckConsistency();
+
+  void *pointer = allocator_->Alloc(0);
+  ASSERT_FALSE(pointer);
+  EXPECT_TRUE(allocator_->CheckConsistency());
+}
+
 // Checks out-of-memory condition.
 TEST_F(FencedAllocatorWrapperTest, TestOutOfMemory) {
   allocator_->CheckConsistency();