[fpc-devel] Compiler limitations

Daniël Mantione daniel.mantione at freepascal.org
Fri May 9 23:01:45 CEST 2008

Op Fri, 9 May 2008, schreef Florian Klaempfl:

> Vincent Snijders schrieb:
>> Florian Klaempfl schreef:
>>> Miklos Cserzo schrieb:
>>>> Hi Folks,
>>>> according the documentation "Arrays are limited to 2 GBytes in size in 
>>>> the default processor mode." Is there another mode allowing bigger 
>>>> arrays?
>>> 64 Bit mode/compiler.
>> Except for darwin.
>> Except it doesn't work:
>> http://www.freepascal.org/testsuite/cgi-bin/testsuite.cgi?action=3&run1id=21737&testfileid=2417 
> This is operation system dependent also if you can declare static data 
> structures of this size. Things like
> type
>  ta = array[0..$fffffffff] of byte;
> var
>  p : ^ta;
> begin
>  new(p);
> end.
> should work e.g. on linux.

Yes, this would work, but wrapping it in a record and adding a field to it 
might not work. The reason is that the x86_64 still uses singed 32-bit 
displacements in its operands. To support this, a different code 
generation is needed, which we don't have.

Many compilers have an mcmodel switch. FPC's x86_64 code generation 
compares to mcmodel=small.


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