Multibyte paddings fine for some situations and I think all compliers for
these targets do it. However Im talking about receiving comms data as byte
streams, a different matter entirely
If a structure of words is recieved over a serial link as a byte stream then
you dont know if if the words are aligned or not.
You can either read it all as bytes and recombine it yourself - therefore
not being able to overlay a structure.
or see if the first byte is at an odd address and if so do a MemMove
(source_address+1,source_adress, len) to align it all.
Most compliers sort this out for you.
> -----Original Message-----
> From: Roger Chaplin [SMTP:[EMAIL PROTECTED]]
> Sent: 28 July 2000 15:56
> To: Palm Developer Forum
> Subject: RE: Compiler - Cannot convert signed char * to char *
>
> Richard Anderson <[EMAIL PROTECTED]> wrote:
>
> > On the pointer front:
> >
> > I dont expect the compiler to change the pointer but take this
> example
> > (psudo addresses):
> >
> > I receive 3 bytes of serial data and place them at address 0x100
> >
> > if my data is infact:
> >
> > struct {
> > char a;
> > word b;
> > } mystruct;
> >
> > And I have a pointer to mystruct overlayed on my serial data
> >
> > mystruct *ptr = 0x100;
> >
> > and do : word c = *mystruct->b then you get a bus error as
> the
> > compiler does a move.w over a odd boundary.
> > What it should do is 2 * move.b and recombine the result
> transparently to
> > the C user. Other 68K compiler I have used do this.
>
> Ah, okay. Are you sure about the two move.b instructions? Most
> compilers I've seen that are targetted to architectures requiring even
> address for multi-byte accesses accomplish such safety by adding a byte
> of padding as necessary within structs, so that multi-byte elements are
> on even addresses. There should be an option somewhere in the CW
> settings to make it do this.
>
> --
> Roger Chaplin
> <[EMAIL PROTECTED]>
>
> --
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