mono/tests/sizeof-empty-structs.cs

   1 using System;
   2 using System.Runtime.InteropServices;
   3 using System.Reflection;
   4 using System.Linq;
   5
   6 public struct EmptyStruct {
   7 }
   8
   9 [StructLayout(LayoutKind.Sequential)]
  10 public struct EmptySequentialStruct {
  11 }
  12
  13 [StructLayout(LayoutKind.Explicit)]
  14 public struct EmptyExplicitStruct {
  15 }
  16
  17 [StructLayout(LayoutKind.Sequential, Pack = 4)]
  18 public struct EmptySequentialPackStruct {
  19 }
  20
  21 [StructLayout(LayoutKind.Explicit, Pack = 4)]
  22 public struct EmptyExplicitPackStruct {
  23 }
  24
  25 [StructLayout(LayoutKind.Explicit, Size = 0)]
  26 public struct EmptyExplicitSize0Struct {
  27 }
  28
  29 [StructLayout(LayoutKind.Explicit, Size = 1)]
  30 public struct EmptyExplicitSize1Struct {
  31 }
  32
  33 [StructLayout(LayoutKind.Sequential, Pack = 1)]
  34 public struct TestOffsets {
  35     public int A;
  36     public EmptyStruct B;
  37     public int C;
  38     public EmptyExplicitSize0Struct D;
  39     public int E;
  40     public EmptySequentialStruct F;
  41     public int G;
  42 }
  43
  44 class Program {
  45     private static unsafe void CheckSize<T> (int expected, ref int exitCode) {
  46         var t = typeof(T);
  47         var actualSize = Marshal.SizeOf(t);
  48
  49         Console.WriteLine($"Marshal.SizeOf({t.Name}) == {actualSize}, expected {expected}");
  50
  51         if (actualSize != expected)
  52             exitCode += 1;
  53     }
  54
  55     // https://bugzilla.xamarin.com/show_bug.cgi?id=18941
  56     // Marshal.SizeOf should never report 0, even for empty structs or structs with Size=0 attribute
  57     public static int Main () {
  58         int exitCode = 0;
  59
  60         CheckSize<EmptyStruct>(1, ref exitCode);
  61         CheckSize<EmptySequentialStruct>(1, ref exitCode);
  62         CheckSize<EmptyExplicitStruct>(1, ref exitCode);
  63         CheckSize<EmptySequentialPackStruct>(1, ref exitCode);
  64         CheckSize<EmptyExplicitPackStruct>(1, ref exitCode);
  65         CheckSize<EmptyExplicitSize0Struct>(1, ref exitCode);
  66         CheckSize<EmptyExplicitSize1Struct>(1, ref exitCode);
  67         CheckSize<TestOffsets>(19, ref exitCode);
  68
  69         Console.WriteLine("--");
  70
  71         var t = typeof(TestOffsets);
  72         var actualOffsets = (
  73             from f in t.GetFields()
  74             select (name: f.Name, offset: Marshal.OffsetOf(t, f.Name).ToInt32())
  75         ).ToList();
  76
  77         var expectedOffsets = new [] {
  78             (name: "A", offset: 0),
  79             (name: "B", offset: 4),
  80             (name: "C", offset: 5),
  81             (name: "D", offset: 9),
  82             (name: "E", offset: 10),
  83             (name: "F", offset: 14),
  84             (name: "G", offset: 15)
  85         };
  86
  87         if (!actualOffsets.SequenceEqual(expectedOffsets)) {
  88             Console.WriteLine("Field offset mismatch:");
  89
  90             for (int i = 0; i < expectedOffsets.Length; i++) {
  91                 var expected = expectedOffsets[i];
  92                 var actual = actualOffsets[i];
  93                 Console.WriteLine($"OffsetOf({t.Name}.{actual.name}) == {actual.offset}, expected OffsetOf({expected.name}) == {expected.offset}.");
  94             }
  95         }
  96
  97         return exitCode;
  98     }
  99 }