[fpc-pascal] RECORD alignment issue on Mac OS X intel based

Jonas Maebe jonas.maebe at elis.ugent.be
Mon Apr 27 18:18:48 CEST 2009

On 27 Apr 2009, at 17:34, Roland Turcan wrote:

>> The fact is, that FPC compiler on intel based Mac OS X builds up
>> application which contains records "packed" by 4 bytes by default.
>> I need to get the same behavior in intel based mac os x as I have in
>> other platforms.

If you do not specify any "packrecords" setting, the compiler can do  
whatever it wants with the internal alignment of the record (and this  
can be different not only between different platforms, but also  
between different compiler versions). If you want a particular layout,  
use a particular packrecords setting ({$packrecords 1} with manual  
padding is probably the safest). See also http://wiki.freepascal.org/User_Changes_Trunk#Alignment_of_record_variables

One reason that it can be different on different platforms, is that  
the alignment of some types may be defined differently by the ABI  
(e.g., the Mac OS X/i386 ABI defines the alignment of double variables  
as 4 bytes, while on most other ABIs it's 8 bytes).


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