Fix AV in gc_heap::init_heap_segment

src/coreclr/gc/card_table.cpp

@@ -221,7 +221,7 @@ void gc_heap::get_card_table_element_layout (uint8_t* start, uint8_t* end, size_
     for (int element = brick_table_element; element <= total_bookkeeping_elements; element++)
     {
         layout[element] = layout[element - 1] + sizes[element - 1];
-        if ((element != total_bookkeeping_elements) && (sizes[element] != 0))
+        if (element != total_bookkeeping_elements)
         {
             layout[element] = ALIGN_UP(layout[element], alignment[element]);
         }

src/tests/GC/Regressions/Github/Runtime_129681/Runtime_129681.cs

@@ -0,0 +1,53 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using Xunit;
+
+public class Runtime_129681
+{
+    private const int StorageLength = 8192;
+
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        object[] storage = new object[StorageLength];
+        int index = 0;
+
+        try
+        {
+            while (index < storage.Length)
+            {
+                storage[index++] = GC.AllocateArray<byte>(16 * 1024, pinned: true);
+            }
+        }
+        catch (OutOfMemoryException)
+        {
+        }
+
+        try
+        {
+            while (index < storage.Length)
+            {
+                storage[index++] = GC.AllocateArray<byte>(256, pinned: true);
+            }
+        }
+        catch (OutOfMemoryException)
+        {
+        }
+
+        try
+        {
+            while (index < storage.Length)
+            {
+                storage[index++] = GC.AllocateArray<byte>(1, pinned: true);
+            }
+        }
+        catch (OutOfMemoryException)
+        {
+            return;
+        }
+
+        throw new Exception("The configured GC heap hard limit was not reached.");
+    }
+}

src/tests/GC/Regressions/Github/Runtime_129681/Runtime_129681.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+    <CLRTestPriority>1</CLRTestPriority>
+    <DisableProjectBuild Condition="'$(RuntimeFlavor)' == 'mono'">true</DisableProjectBuild>
+
+    <CLRTestBatchPreCommands><![CDATA[
+      $(CLRTestBatchPreCommands)
+      set DOTNET_GCStress=0xC
+      set DOTNET_GCHeapHardLimit=0x4000000
+      set DOTNET_GCRegionRange=0x4000000
+      set DOTNET_GCRegionSize=0x100000
+      ]]></CLRTestBatchPreCommands>
+    <CLRTestBashPreCommands><![CDATA[
+      $(CLRTestBashPreCommands)
+      export DOTNET_GCStress=0xC
+      export DOTNET_GCHeapHardLimit=0x4000000
+      export DOTNET_GCRegionRange=0x4000000
+      export DOTNET_GCRegionSize=0x100000
+      ]]></CLRTestBashPreCommands>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>