structure alignment issues?

[akcom]

akcom wrote:
> Translating the following from windows:
> 
> --- C Code:
> 
> #define IMAGE_SIZEOF_SHORT_NAME              8
> 
> typedef struct _IMAGE_SECTION_HEADER {
>     BYTE    Name[IMAGE_SIZEOF_SHORT_NAME];
>     union {
>             DWORD   PhysicalAddress;
>             DWORD   VirtualSize;
>     } Misc;
>     DWORD   VirtualAddress;
>     DWORD   SizeOfRawData;
>     DWORD   PointerToRawData;
>     DWORD   PointerToRelocations;
>     DWORD   PointerToLinenumbers;
>     WORD    NumberOfRelocations;
>     WORD    NumberOfLinenumbers;
>     DWORD   Characteristics;
> } IMAGE_SECTION_HEADER, *PIMAGE_SECTION_HEADER;
> 
> #define IMAGE_SIZEOF_SECTION_HEADER          40
> 
> --- D Code:
> 
> const uint IMAGE_SIZEOF_SHORT_NAME = 8;
> const uint IMAGE_SIZEOF_SECTION_HEADER = 40;
> 
> align struct ImageSectionHeader
> {
>     BYTE    Name[IMAGE_SIZEOF_SHORT_NAME];
>     union Misc
>     {
>             DWORD   PhysicalAddress;
>             DWORD   VirtualSize;
>     }
>     DWORD   VirtualAddress;
>     DWORD   SizeOfRawData;
>     DWORD   PointerToRawData;
>     DWORD   PointerToRelocations;
>     DWORD   PointerToLinenumbers;
>     WORD    NumberOfRelocations;
>     WORD    NumberOfLinenumbers;
>     DWORD   Characteristics;
> }
> alias ImageSectionHeader IMAGE_SECTION_HEADER;
> alias ImageSectionHeader *PIMAGE_SECTION_HEADER;
> 
> the problem is that ImageSectionHeader.sizeof == 36
> Any ideas as to why?

edit:
it appears as if when the union is replaced by a single DWORD, 
everything works as expected.  Should this be filed as a bug?