[fpc-devel] Packed record integers and x86_86

[J. Gareth Moreton]

 I think the official unsigned 32-bit integer type in Pascal is "LongWord".
 As others have said, be aware that pointers are 64-bit under x64... that's
kind of why it's called x64!  If you absolutely must have a packed record
with 32-bit types, I recommend changing Sender and Target to indices that
are added to a base address.
 Similar to what Pierre said, change your Pointer code to something like
this:
 for Indx := 0 to SizeOf(TTCPPackageHeader) - 1 do
Dec(Byte(Pointer(PtrUInt(@x) + Indx)^), ARollCount);

 So similarly with your record, instead of directly derefencing Sender and
Target - since I assume your record type must stay fixed at 15 bytes - have
something akin to "Pointer(PtrUInt(@BaseAddr) + Sender)".

 The first rule, first and foremost... don't assume the Pointer is a fixed
size.  Hope all of this helps.

 Gareth aka. Kit
 P.S. I would recommend adding a "Filler" or "Reserved" byte at the end of
your record type to make it 16 bytes long - such a size is more efficient
when it's part of an array in memory.

 On Wed 27/03/19 21:11 , Pierre Muller pierre at freepascal.org sent:

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 > 
 > 
 > Pointer arithmetic: 
 > *for Indx := 0 to SizeOf(TTCPPackageHeader) - 1 do
Dec(Byte(Pointer(Cardinal(@x) + Indx)^), ARollCount);* 
 the error has nothing to do with your record, 
 its that part: 
 Pointer(Cardinal(@x) + Indx)^) 

 The problem is that Cardinale is an unsigned 32-bit integer, 
 while on 64-bit, you will need UINT64, 

 You should use PtrUInt type that is an unsigned type 
 that always have the size of an address instead of cardinal here! 

 Pierre 
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