Re: [Sdcc-user] Internal registers not found

[Raphael N. <rn...@we...>]

Hi Alan,

Sorry for having ported the wrong version; I just googled for picos and
found that one...

> These functions are defined as extern and prefixed by underscore at
> the header file, but the compiler is not placing they at "extern
> variables in this module" section into generated asm file. I tested
> removing the underscore from header declaration with no success.

Yes, this is a bug... Unused (or ones used only in inline assembly
fragment and thus effectively hidden from the compiler) extern
declarations are discarded; as a consequence, they do not appear in the
.asm file as EXTERN SYMBOL nor EXTERN _SYMBOL and hence cannot be
resolved by the assembler. Sigh...

The really bad workaround is to effectively access the symbols in c:
    extern void _kernel(void);
with _kernel being only referenced in _asm ... _endasm; blocks such as
    _asm goto _kernel _endasm;
should (for now) be rewritten as
    extern kernel; // Note: SDCC mangles this into _kernel
    static void *k = &kernel; // WORKAROUND SDCC BUG

As I said, the workaround is really bad: It is both a maintenance
nightmare and even costs memory space at runtime! I really need to look
into a way of emitting even unused externs...

Assembler symbols with no leading underscore need to be rewritten in the
defining .asm (or better .S) file to have a leading underscore if they
are to be accessed from C (which includes all symbols that need the
above workaround):

	global tsk_1_stack
tsk_1_stack res 15
	global great_function
great_function:
	return

becomes
	global _tsk_1_stack
_tsk_1_stack res 15
	global _great_function
_great_function:

Alternatively one might introduce an option for SDCC not to add a
leading underscore to user-defined symbols, probably risking name
clashes with compiler-defined symbols...

Regards,
Raphael