[Mono-bugs] [Bug 74798][Nor] New - mono/.NET behavior difference with "union" structs

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Changed by danw@novell.com.

http://bugzilla.ximian.com/show_bug.cgi?id=74798

--- shadow/74798	2005-05-02 12:09:25.000000000 -0400
+++ shadow/74798.tmp.8440	2005-05-02 12:09:25.000000000 -0400
@@ -0,0 +1,41 @@
+Bug#: 74798
+Product: Mono: Runtime
+Version: 1.1
+OS: 
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Normal
+Component: misc
+AssignedTo: mono-bugs@ximian.com                            
+ReportedBy: danw@novell.com               
+QAContact: mono-bugs@ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: mono/.NET behavior difference with "union" structs
+
+I tried creating a struct basically like this:
+
+  [StructLayout (LayoutKind.Explicit)]
+  public struct Foo {
+      [FieldOffset (0)] public int foo;
+      [FieldOffset (0)] public EventHandler bar;
+  }
+
+which worked fine until I tried using it as the key in a hash table,
+at which point the program crashed with an unhandled exception because
+it was trying to hash the int value as though it was an EventHandler.
+Overriding Foo's GetHashCode() method to only look at the int field made
+everything work fine.
+
+I went to compare this against .NET's behavior though, and discovered
+that .NET won't even load the assembly:
+
+  An unhandled exception of type 'System.TypeLoadException' occurred
+  in foo.exe
+
+  Additional information: Could not load type Foo from assembly 0
+  because it contains an object field at offset 0 that is incorrectly
+  aligned or overlapped by a non-object field.