Yeah, sorry... I'd been hacking on that all day with no success, and was more
than a little cranky. Let me try again:
The global absolute label CSRX=0xF63A is the address of the X co-ordinate of
the cursor on the screen. ("Im picking on it because it's the first variable to
appear in m100.def.) A declaration of "extern char *CSRX" tells the compiler
about it. So far so good right?
(I don't know if writing to that value is a good plan? Never tried it?)
Anyway, the compiled smallc code can see the label CSRX. Unfortunately there
seems to be no way to actually get it. :-(
The problem is that when smallc's generated code references a data label, it
does so indirectly, both the data segment of the same source, and extern
sources. Hence it emits "lhld CSRX" which loads HL with the 16-bit value
pointed to by CSRX, and then treats whatever the cursor X position and
whatever the next byte is as a pointer. Not right!!!!! What I need it to do is
a simple "lxi h,CSRX" but that opcode is only generated when loading a constant
from the source. :-(
So when an int foo is delcared, the label foo is treated as a pointer to a DW
word. What I need, and the compiler has no way to offer, is a way to force that
indirection to be skipped. :-(
Anyway, I've given up on that, I've got other stuff to test and more wrapper
functions to write.
BTW it's going to look like main(char A, int HL) {}!!!! (Assuming it doeesn't
find some weird way to screw with me there.I have to say, abandoning the
standard library is a very liberating experience.... :-)
Willard
Sent from Samsung tablet
-------- Original message --------
From "John R. Hogerhuis" <[email protected]>
Date: 03/23/2017 12:02 PM (GMT-07:00)
To Model 100 Discussion <[email protected]>
Subject Re: [M100] Smallc tech note
On Thu, Mar 23, 2017 at 1:55 AM, Willard Goosey <[email protected]> wrote:
Grrrr!!!!!!!
Ok, so. My m100.def has, for SmallC purposes, 3 classes of equates. ROM
function that don't require arguments or return values, ROM functions that do
require args or return values, and system variables.
Because I use sed to translate the ASM/ZMAC original equates into ASX syntax
global equates, these all end up as global labels that are stored, name and
value, in the .rel object files. This means that the first class of functions
can be called with no further code from Small C. The second type of function
requires wrapper functions. And that's. All good.
And I really really hoped that the system variables would be as easily used.
Unfortunately it's not to be. A reference to extern char *CRSX (x=CRSX)
generates "lhld CRSX \n mov a,m" when what I need is "lxi h, CRSX\n mov a,m" .
I am very sad.
I've looked through the code generator already and there's no hope. It looks
like the best I can do is have the system variable names as #defines. Anything
else would result in a huge tabke of pointers in the .co file that might not
even be used!
It's not clear to me how you're expecting it to work. You want it to derefence
the pointer without you telling it to?
I'd think if you want to access the char referred to by the pointer at the
address, you need to dereference the pointer.
extern char *CSRX;
char x;
x = *CSRX;
*CSRX = 0x65;
or are you talking about the address of a pointer
extern char **CSRX;
-- John.
