I have this structure:
[StructLayout(LayoutKind.Sequential, Pack = 8)]
unsafe struct MyStruct_t
{
public UInt32 ulID;
public fixed Byte xValue[32];
}
and then i run this command to get the size:
Console.WriteLine("Marshal.SizeOf(typeof(MyStruct_t))= {0}", Marshal.SizeOf(typeof(MyStruct_t)));
and the answer is consistently
Marshal.SizeOf(typeof(MyStruct_t))= 36
I was expecting 40. Am i missing something? Is there something i do not understand in the meaning of Pack=8?
From MSDN :
The fields of a type instance are aligned by using the following rules:
- The alignment of the type is the size of its largest element (1, 2, 4, 8, etc., bytes) or the specified packing size, whichever is smaller .
You have a Pack=8
, but your largest size element is 4 (the UInt32
). The lesser of 8 and 4 is 4.
If you want your struct to be 40 bytes, you'll have to add 4 bytes of "padding".
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