From 208ca9fafdbf53bb41213834bba697cad2b4ff5d Mon Sep 17 00:00:00 2001
From: assiduous <assiduous@diligentgraphics.com>
Date: Thu, 13 Feb 2020 11:29:06 -0800
Subject: FixedBlockMemoryAllocator: fixed issue with block size alignment by
 sizeof(void*)

---
 Common/interface/FixedBlockMemoryAllocator.hpp     |  4 +--
 Common/src/FixedBlockMemoryAllocator.cpp           | 21 +++++++-----
 .../DiligentCoreTest/src/Common/AllocatorTest.cpp  | 40 ++++++++++++++++++++++
 3 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/Common/interface/FixedBlockMemoryAllocator.hpp b/Common/interface/FixedBlockMemoryAllocator.hpp
index a21e41d1..89c9e355 100644
--- a/Common/interface/FixedBlockMemoryAllocator.hpp
+++ b/Common/interface/FixedBlockMemoryAllocator.hpp
@@ -229,8 +229,8 @@ private:
     std::mutex m_Mutex;
 
     IMemoryAllocator& m_RawMemoryAllocator;
-    size_t            m_BlockSize;
-    Uint32            m_NumBlocksInPage;
+    const size_t      m_BlockSize;
+    const Uint32      m_NumBlocksInPage;
 };
 
 IMemoryAllocator& GetRawAllocator();
diff --git a/Common/src/FixedBlockMemoryAllocator.cpp b/Common/src/FixedBlockMemoryAllocator.cpp
index 8235edc0..bca872fa 100644
--- a/Common/src/FixedBlockMemoryAllocator.cpp
+++ b/Common/src/FixedBlockMemoryAllocator.cpp
@@ -26,11 +26,18 @@
  */
 
 #include "pch.h"
+#include <algorithm>
 #include "FixedBlockMemoryAllocator.hpp"
+#include "Align.hpp"
 
 namespace Diligent
 {
 
+static size_t AdjustBlockSize(size_t BlockSize)
+{
+    return Align(std::max(BlockSize, size_t{1}), sizeof(void*));
+}
+
 FixedBlockMemoryAllocator::FixedBlockMemoryAllocator(IMemoryAllocator& RawMemoryAllocator,
                                                      size_t            BlockSize,
                                                      Uint32            NumBlocksInPage) :
@@ -38,16 +45,13 @@ FixedBlockMemoryAllocator::FixedBlockMemoryAllocator(IMemoryAllocator& RawMemory
     m_PagePool          (STD_ALLOCATOR_RAW_MEM(MemoryPage, RawMemoryAllocator, "Allocator for vector<MemoryPage>")),
     m_AvailablePages    (STD_ALLOCATOR_RAW_MEM(size_t, RawMemoryAllocator, "Allocator for unordered_set<size_t>") ),
     m_AddrToPageId      (STD_ALLOCATOR_RAW_MEM(AddrToPageIdMapElem, RawMemoryAllocator, "Allocator for unordered_map<void*, size_t>")),
-    m_RawMemoryAllocator{RawMemoryAllocator},
-    m_BlockSize         {BlockSize         },
-    m_NumBlocksInPage   {NumBlocksInPage   }
+    m_RawMemoryAllocator{RawMemoryAllocator        },
+    m_BlockSize         {AdjustBlockSize(BlockSize)},
+    m_NumBlocksInPage   {NumBlocksInPage           }
 // clang-format on
 {
-    if (BlockSize > 0)
-    {
-        // Allocate one page
-        CreateNewPage();
-    }
+    // Allocate one page
+    CreateNewPage();
 }
 
 FixedBlockMemoryAllocator::~FixedBlockMemoryAllocator()
@@ -70,6 +74,7 @@ void FixedBlockMemoryAllocator::CreateNewPage()
 
 void* FixedBlockMemoryAllocator::Allocate(size_t Size, const Char* dbgDescription, const char* dbgFileName, const Int32 dbgLineNumber)
 {
+    Size = AdjustBlockSize(Size);
     VERIFY(m_BlockSize == Size, "Requested size (", Size, ") does not match the block size (", m_BlockSize, ")");
 
     std::lock_guard<std::mutex> LockGuard(m_Mutex);
diff --git a/Tests/DiligentCoreTest/src/Common/AllocatorTest.cpp b/Tests/DiligentCoreTest/src/Common/AllocatorTest.cpp
index 3d074246..00df04f2 100644
--- a/Tests/DiligentCoreTest/src/Common/AllocatorTest.cpp
+++ b/Tests/DiligentCoreTest/src/Common/AllocatorTest.cpp
@@ -80,4 +80,44 @@ TEST(Common_FixedBlockMemoryAllocator, AllocDealloc)
                 TestAllocator.Free(Allocations[i][p]);
 }
 
+TEST(Common_FixedBlockMemoryAllocator, SmallObject)
+{
+    constexpr Uint32 AllocSize             = 4;
+    constexpr Uint32 NumAllocationsPerPage = 1;
+
+    FixedBlockMemoryAllocator TestAllocator(DefaultRawMemoryAllocator::GetAllocator(), AllocSize, NumAllocationsPerPage);
+
+    {
+        void* pRawMem0 = TestAllocator.Allocate(AllocSize, "Small object allocation test", __FILE__, __LINE__);
+        TestAllocator.Free(pRawMem0);
+    }
+
+    {
+        void* pRawMem0 = TestAllocator.Allocate(AllocSize, "Small object allocation test", __FILE__, __LINE__);
+        void* pRawMem1 = TestAllocator.Allocate(AllocSize, "Small object allocation test", __FILE__, __LINE__);
+        TestAllocator.Free(pRawMem0);
+        TestAllocator.Free(pRawMem1);
+    }
+}
+
+TEST(Common_FixedBlockMemoryAllocator, UnalignedSize)
+{
+    constexpr Uint32 AllocSize             = 10;
+    constexpr Uint32 NumAllocationsPerPage = 1;
+
+    FixedBlockMemoryAllocator TestAllocator(DefaultRawMemoryAllocator::GetAllocator(), AllocSize, NumAllocationsPerPage);
+
+    {
+        void* pRawMem0 = TestAllocator.Allocate(AllocSize, "Unaligned-size object allocation test", __FILE__, __LINE__);
+        TestAllocator.Free(pRawMem0);
+    }
+
+    {
+        void* pRawMem0 = TestAllocator.Allocate(AllocSize, "Unaligned-size object allocation test", __FILE__, __LINE__);
+        void* pRawMem1 = TestAllocator.Allocate(AllocSize, "Unaligned-size object allocation test", __FILE__, __LINE__);
+        TestAllocator.Free(pRawMem0);
+        TestAllocator.Free(pRawMem1);
+    }
+}
+
 } // namespace
-- 
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