RE: [GD-Windows] using typedef to create aligned types

[Andrew G. <ag...@cl...>]

You're changing the alignment, not the size.

Alignment determines where a variable will be allocated in memory, e.g
FredAligned16 will always be allocated on a 16 byte memory boundry but the
size of both types will be the same.


A.
 

> -----Original Message-----
> From: gam...@li... 
> [mailto:gam...@li...] On 
> Behalf Of Andras Balogh
> Sent: Wednesday, December 01, 2004 3:46 PM
> To: gam...@li...
> Subject: [GD-Windows] using typedef to create aligned types
> 
> MSDN says that I can use typedef to make aligned versions of 
> my types, eg:
> 
> typedef __declspec(align(16)) Fred FredAligned16;
> 
> This works when I declare variables, eg:
> 
> Fred fred1;
> FredAligned16 fred2;	
> 
> fred2 is 16 bytes aligned, while fred1 is not
> 
> But the strange thing is that sizeof(Fred) == 
> sizeof(FredAligned16) is true, even though Fred's size is not 
> a multiple of 16 bytes...
> 
> When I declare different types (ie. not using typedef), then 
> the sizeof will be different because the aligned type will be 
> padded to the next multiple of
> 16 bytes.
> 
> Is this a bug in the compiler??
> 
> 
> 
> Thanks,
> 
> Andras
> 
> 
> 
> 
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