[fpc-pascal] Variable alignment in arm-embedded

Florian Klaempfl florian at freepascal.org
Tue Jun 12 20:08:00 CEST 2012

Am 12.06.2012 09:50, schrieb Koenraad Lelong:
> On 08-06-12 14:37, Jeppe Græsdal Johansen wrote:
>> Den 08-06-2012 14:28, Ludo Brands skrev:
>>>> Thanks Ludo,
>>>> I'll take that as a starting point. I hope I will not need the "lost"
>>>> 256 bytes in the future.
>>> I could be wrong but AFAIK if the compiler would do the alignment, the
>>> loss
>>> can also be up to 255 bytes. Here you lose 256 bytes in all cases.
>> Yes, but this would allow the linker to place other stuff there which
>> fits in less than 255 bytes.
>> Wasting 255 bytes is a lot on systems that only has a few kilobytes of
>> RAM. I wonder if the restriction of 32 bytes on the align directive
>> could just be removed, or will we need some sort of linker script
>> changes?
> Hi,
> I'm still struggling to get interrupts (or even inputs) work but I
> wanted to comment on the size of the table. Reading the manuals I found
> it's actually on a 512 byte boundery. The VTOR (Vector Table Offset
> Register) masks off the last 9 bits (8..0).
> If I need that space I will modify the start of RAM location and use the
> first bytes of RAM for the vector-table.
> It would be nice to have "external" linker scripts. That way you could
> more easily add processors,

I think extending t_embedded.pas is the more clean solution to add new 
controllers, especially because it makes it easier for other people to 
use the added controllers.

> or use custom bootloaders.
> Regards,
> Koenraad Lelong.
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