RE: [Sdcc-user] Help chasing a struct bug?

[Josh S. <jo...@4s...>]

Your 'dd' declaration is being created in the code segment.  This is because
it is a constant.  The issue here is that the asm for test.c is created
before it knows where dd is stored.  Your extern statement does not specify
that dd is a constant, so test.asm is created assuming that dd will be in
the idata section.  If you add a const qualifier on your extern, it should
work fine.  I didn't try it myself, but the generated code is now correct...


Josh Stone


> -----Original Message-----
> From: sdc...@li...
> [mailto:sdc...@li...]On Behalf Of Scott Bronson
> Sent: Monday, July 28, 2003 6:20 PM
> To: sdc...@li...
> Subject: [Sdcc-user] Help chasing a struct bug?
>
>
> I think I've found a bug in SDCC, but because I'm not
> real confident of my understanding of pointers and 8051
> memory areas, I'm not sure.
>
> Here's the deal:  If I define a structure in the C file
> in which it is used, weverything works perfectly.  However,
> if I define the structure in another C file
> ("extern DeviceDescriptor dd;"), it goes horribly wrong.
> I get garbage when I read from the structure (the simulator
> always returns 0, and my 8051 dev board returns values from
> code memory).
>
>
> Here's how to reproduce this using the attached code.
>
> 1. Verify that INCLUDE_DD is set to 1 in dd.h
> 2. "make sim", and in another window "make net"
> 3. Type "go" in the simulator window.  Notice how
>    the serial output is correct:  "dd.length: 42"
>
> 4. Set INCLUDE_DD to 0 in dd.h.  This means that
>    the dd struct will be defined in dd.c rather
>    than test.c.
> 5. "make sim", "make net"
> 6. "go".  Serial output: "dd.length: 0"
>
> Can anyone tell me what's going wrong?  Thanks,
>
>      - Scott
>
>