Round struct sizes up to their alignment

src/FlatSharp/TypeModel/StructTypeModel.cs

@@ -256,6 +256,9 @@ public override void Validate()
             this.inlineSize += length;
         }
 
+        // FlatBuffers spec requires the size to be a multiple of the alignment (equivalent to flatc PadLastField).
+        this.inlineSize += SerializationHelpers.GetAlignmentError(this.inlineSize, this.maxAlignment);
+
         foreach (StructMemberModel member in this.memberTypes)
         {
             ITypeModel memberModel = member.ItemTypeModel;

src/FlatSharp/TypeModel/ValueStructTypeModel.cs

@@ -182,7 +182,7 @@ public override CodeGeneratedMethod CreateSerializeMethodBody(SerializationCodeG
         {
             body = $@"
                 {slice}
-                
+
                 {StrykerSuppressor.SuppressNextLine("boolean")}
                 if ({StrykerSuppressor.BitConverterTypeName}.IsLittleEndian)
                 {{
@@ -308,6 +308,9 @@ public override void Initialize()
             this.inlineSize += propertyModel.PhysicalLayout[0].InlineSize;
         }
 
+        // FlatBuffers spec requires the size to be a multiple of the alignment (equivalent to flatc PadLastField).
+        this.inlineSize += SerializationHelpers.GetAlignmentError(this.inlineSize, this.maxAlignment);
+
         this.isExternal = this.ClrType.GetCustomAttribute<ExternalDefinitionAttribute>() is not null;
         this.CanMarshalOnSerialize = false;
         this.CanMarshalOnParse = false;

src/Tests/FlatSharpEndToEndTests/FlatSharpEndToEndTests.csproj

@@ -10,7 +10,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <Nullable>annotations</Nullable>
     <DocumentationFile>$(OutputPath)$(AssemblyName).xml</DocumentationFile>
-    <NoWarn>CS1591</NoWarn>
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
     <RunAnalyzersDuringLiveAnalysis>False</RunAnalyzersDuringLiveAnalysis>
     <EnableNETAnalyzers>True</EnableNETAnalyzers>
     <AnalysisLevel>latest</AnalysisLevel>

src/Tests/FlatSharpEndToEndTests/ValueStructs/ValueStructTests.cs

@@ -76,7 +76,7 @@ public void WriteThrough_ValueStruct_InTable()
     [TestMethod]
     public void Basics()
     {
-        Assert.AreEqual(36, Unsafe.SizeOf<ValueStruct>());
+        Assert.AreEqual(40, Unsafe.SizeOf<ValueStruct>());
     }
 
     [TestMethod]
@@ -189,8 +189,13 @@ public void ValueStructs_UnityNative_WellAligned_Serialize(FlatBufferDeserializa
         }
     }
 
+    /// <summary>
+    /// PoorlyAligned's fields end at 5, but its size is padded up to 8 to match its alignment, so
+    /// elements can be laid out sequentially and the unsafe span path applies.
+    /// </summary>
     [TestMethod]
-    public void ValueStructs_UnityNative_PoorlyAligned_Serialize()
+    [DynamicData(nameof(DynamicDataHelper.DeserializationModes), typeof(DynamicDataHelper))]
+    public void ValueStructs_UnityNative_PoorlyAligned_Serialize(FlatBufferDeserializationOption option)
     {
         int count = 10;
 
@@ -200,8 +205,15 @@ public void ValueStructs_UnityNative_PoorlyAligned_Serialize()
             PoorlyAligned = new(Enumerable.Range(0, count).Select(x => new PoorlyAligned { X = x, Y = 1, }).ToArray(), default),
         };
 
-        var ex = Assert.ThrowsException<InvalidOperationException>(() => source.AllocateAndSerialize());
-        Assert.AreEqual("Type 'FlatSharpEndToEndTests.ValueStructs.PoorlyAligned' does not support Unsafe Span operations because the size (5) is not a multiple of the alignment (4).", ex.Message);
+        byte[] data = source.AllocateAndSerialize();
+
+        var parsed = UnityVectors_List.Serializer.Parse(data, option);
+
+        for (int i = 0; i < count; ++i)
+        {
+            Assert.AreEqual(source.PoorlyAligned.Value[i].X, parsed.PoorlyAligned[i].X);
+            Assert.AreEqual(source.PoorlyAligned.Value[i].Y, parsed.PoorlyAligned[i].Y);
+        }
     }
 
     [TestMethod]
@@ -251,15 +263,13 @@ public void ValueStructs_UnityNative_PoorlyAligned_Parse(FlatBufferDeserializati
         GCHandle handle = GCHandle.Alloc(data);
         try
         {
-            var ex = Assert.ThrowsException<InvalidOperationException>(() =>
-            {
-                var parsed = UnityVectors_Native.Serializer.Parse(new MemoryInputBuffer(data, true), option);
-                float f = parsed.PoorlyAligned.Value[0].X;
-            });
+            var parsed = UnityVectors_Native.Serializer.Parse(new MemoryInputBuffer(data, true), option);
 
-            Assert.AreEqual(
-                "Type 'FlatSharpEndToEndTests.ValueStructs.PoorlyAligned' does not support Unsafe Span operations because the size (5) is not a multiple of the alignment (4).",
-                ex.Message);
+            for (int i = 0; i < count; ++i)
+            {
+                Assert.AreEqual(source.PoorlyAligned[i].X, parsed.PoorlyAligned.Value[i].X);
+                Assert.AreEqual(source.PoorlyAligned[i].Y, parsed.PoorlyAligned.Value[i].Y);
+            }
         }
         finally
         {

src/Tests/Stryker/CodeGen/CodeGen.csproj

@@ -8,7 +8,7 @@
     <RootNamespace>FlatSharpStrykerTests</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <Nullable>annotations</Nullable>
-    <NoWarn>CS1591</NoWarn>
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>

src/Tests/Stryker/CodeGen/Schema.fbs

@@ -16,7 +16,7 @@ enum Fruit : int
     Pear
 }
 
-/// Poorly Aligned. Total Size = 10, Alignment = 4
+/// Poorly Aligned. Fields end at 10, Total Size = 12, Alignment = 4
 struct ValueStruct (fs_valueStruct)
 {
     /// Position 0, Length 4, Alignment 4
@@ -29,7 +29,7 @@ struct ValueStruct (fs_valueStruct)
     c : [ short : 2 ] (fs_unsafeStructVector);
 }
 
-/// Poorly aligned. Total Size == 26, Alignemnt = 8
+/// Poorly aligned. Fields end at 28, Total Size == 32, Alignemnt = 8
 struct RefStruct
 {
     /// Position 0, Length 8, Alignment 8, WriteThrough = true
@@ -44,7 +44,7 @@ struct RefStruct
     /// Position 14, length 2, Alignment 1, WriteThrough = false
     d : [ byte : 2 ];
 
-    /// Position 16, Length 10, Alignment 4, WriteThrough = false
+    /// Position 16, Length 12, Alignment 4, WriteThrough = false
     e : ValueStruct;
 }
 

src/Tests/Stryker/Tests/FullTreeTests.cs

@@ -61,7 +61,7 @@ public void GetMaxSize()
         Root root = this.CreateRoot();
         int maxSize = Root.Serializer.GetMaxSize(root);
 
-        Assert.AreEqual(898, maxSize);
+        Assert.AreEqual(914, maxSize);
     }
 
     [TestMethod]

src/Tests/Stryker/Tests/StructFieldTests.cs

@@ -61,14 +61,15 @@ public void ValueStructTableField(FlatBufferDeserializationOption option)
                     4, 0,               // offset of field 0
                     0, 0,               // padding
 
-                    242, 255, 255, 255, // soffset to vtable
+                    240, 255, 255, 255, // soffset to vtable
                     4, 0, 0, 0,         // valuestruct.a
                     3, 0,               // valuestruct.b, padding
                     1, 0,               // valuestruct.c[0]
                     2, 0,               // valuestruct.c[1]
+                    0, 0,               // valuestruct trailing padding
 
                     8, 0,               // vtable length
-                    14, 0,              // table length
+                    16, 0,              // table length
                     0, 0,               // field 0 (not present)
                     4, 0,               // field 1
                 };
@@ -280,7 +281,7 @@ private static Root CreateRootReferenceStruct(out RefStruct rs, out ValueStruct
             4, 0,               // offset of field 0
             0, 0,               // padding
 
-            226, 255, 255, 255,  // soffset to vtable
+            220, 255, 255, 255,  // soffset to vtable
 
             12, 0, 0, 0,        // refStruct.A (ulong)
             0, 0, 0, 0,
@@ -290,9 +291,11 @@ private static Root CreateRootReferenceStruct(out RefStruct rs, out ValueStruct
             3, 0,               // valuestruct.b, padding
             1, 0,               // valuestruct.c[0]
             2, 0,               // valuestruct.c[1]
+            0, 0,               // valuestruct trailing padding
+            0, 0, 0, 0,         // refStruct trailing padding
 
             6, 0,               // vtable length
-            30, 0,              // table length
+            36, 0,              // table length
             4, 0,               // field 0
         };
 

src/Tests/Stryker/Tests/StrykerTests.csproj

@@ -6,7 +6,7 @@
     <AssemblyName>FlatSharpStrykerTests</AssemblyName>
     <RootNamespace>FlatSharpStrykerTests</RootNamespace>
     <Nullable>annotations</Nullable>
-    <NoWarn>CS1591</NoWarn>
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>

src/Tests/Stryker/Tests/UnionFieldTests.cs

@@ -343,7 +343,8 @@ private Root CreateRoot_RefStructMember(out byte[] expectedData)
             0, 0,               // D[0,1]
             0, 0, 0, 0,         // ValueStruct (default)
             0, 0, 0, 0,
-            0, 0
+            0, 0, 0, 0,         // ValueStruct trailing padding
+            0, 0, 0, 0          // RefStruct trailing padding
         };
 
         return root;
@@ -396,6 +397,7 @@ private Root CreateRoot_ValueStructMember(out byte[] expectedData)
             4, 0,
             1, 0,
             2, 0,
+            0, 0,               // ValueStruct trailing padding
         };
 
         return root;

src/Tests/Stryker/Tests/UnionVectorTests.cs

@@ -281,7 +281,7 @@ private Root CreateRoot(out byte[] expectedData)
             16, 0, 0, 0,
             40, 0, 0, 0,
             52, 0, 0, 0,
-            76, 0, 0, 0,
+            80, 0, 0, 0,
 
             244, 255, 255, 255, // key soffset to vtable
             0, 0, 0, 0,         // apple
@@ -306,6 +306,7 @@ private Root CreateRoot(out byte[] expectedData)
             0, 0, 0, 0,
             0, 0, 0, 0,
             0, 0, 0, 0,
+            0, 0, 0, 0,
 
             1, 0, 0, 0,         // string
             B('c'), 0