[release/7.0] [NativeAOT] Ensure that frozen objects respect the minimum object size (#76050)

* Ensure that frozen objects respect the minimum object size

* Apply feedback

* Handle FrozenStringNode too

Co-authored-by: Filip Navara <[email protected]>

Author: github-actions[bot]

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs

@@ -123,7 +123,10 @@ public override ObjectNodeSection Section
             }
         }
 
-        public int MinimumObjectSize => _type.Context.Target.PointerSize * 3;
+        public int MinimumObjectSize => GetMinimumObjectSize(_type.Context);
+
+        public static int GetMinimumObjectSize(TypeSystemContext typeSystemContext)
+            => typeSystemContext.Target.PointerSize * 3;
 
         protected virtual bool EmitVirtualSlotsAndInterfaces => false;
 

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/FrozenObjectNode.cs

@@ -48,11 +48,20 @@ int ISymbolDefinitionNode.Offset
 
         public override void EncodeData(ref ObjectDataBuilder dataBuilder, NodeFactory factory, bool relocsOnly)
         {
+            int initialOffset = dataBuilder.CountBytes;
+
             // Sync Block
             dataBuilder.EmitZeroPointer();
 
             // byte contents
             _data.WriteContent(ref dataBuilder, this, factory);
+
+            int objectSize = dataBuilder.CountBytes - initialOffset;
+            int minimumObjectSize = EETypeNode.GetMinimumObjectSize(factory.TypeSystemContext);
+            if (objectSize < minimumObjectSize)
+            {
+                dataBuilder.EmitZeros(minimumObjectSize - objectSize);
+            }
         }
 
         protected override string GetName(NodeFactory factory) => this.GetMangledName(factory.NameMangler);

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/FrozenStringNode.cs

@@ -59,6 +59,8 @@ private static IEETypeNode GetEETypeNode(NodeFactory factory)
 
         public override void EncodeData(ref ObjectDataBuilder dataBuilder, NodeFactory factory, bool relocsOnly)
         {
+            int initialOffset = dataBuilder.CountBytes;
+
             dataBuilder.EmitZeroPointer(); // Sync block
 
             dataBuilder.EmitPointerReloc(GetEETypeNode(factory));
@@ -73,6 +75,12 @@ public override void EncodeData(ref ObjectDataBuilder dataBuilder, NodeFactory f
             // Null-terminate for friendliness with interop
             dataBuilder.EmitShort(0);
 
+            int objectSize = dataBuilder.CountBytes - initialOffset;
+            int minimumObjectSize = EETypeNode.GetMinimumObjectSize(factory.TypeSystemContext);
+            if (objectSize < minimumObjectSize)
+            {
+                dataBuilder.EmitZeros(minimumObjectSize - objectSize);
+            }
         }
 
         protected override string GetName(NodeFactory factory) => this.GetMangledName(factory.NameMangler);