F.Klaempfl at gmx.de
Thu Oct 14 00:15:18 CEST 2004
Marc Weustink wrote:
> At 16:38 13-10-2004, Jonas Maebe wrote:
>> On 12 okt 2004, at 22:12, Marc Weustink wrote:
>>> M:> Is a sigbus catchable so that you can read the data and continue
>>> as if nothing happened (or is that something at OS level)
>> That is normally possible, yes. But as Florian said, it's quite a bit
>> of work and also extremely slow (you get 4 context switches per
>> unaligned access, + the work to load the value).
> Yes I do realize that there is a penalty for doing unaligned access.
It's not a penalty, it's death regarding speed ;) A solution I could
imagine is that packed records are accessed correctly, i.e. shifting and
oring but catching sigbus is too much imo and will cause serious
BTW: Does anybody have TP 5.5 for m68k and can test what it does :)?
gpc accesses packed records correctly but it doesn't allow to take the
address of a field of a packed record.
procedure p(var i : integer);
r : packed record
c : char;
i : integer;
r.i:=1; <--- works
p(r.i); <--- test.p:15: packed fields may not be used as `var' parameters
> This will throw away all advantages away form pascal (like strong typing
> And if you forget to make it aligned, you get all kinds of errors.
> I hope I got this all wrong, otherwise I would be better of using a C
> compiler for this (then I've the ability to use macros to get around this)
FPC always tries to do the best of both worlds, I guess you don't want
the gpc behaviour either :)
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