Topic       : The GFA-Basic Compendium
Author      : GFA Systemtechnik GmbH
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View Ref-FileIn larger programs it is generally necessary to avoid using PC-related calls.
In Turbo C, this can be avoided with the -P compiler option.

The C routines must not alter the registers A3 to A6, or expect particular
values from them. Turbo C and DRDigital Research
 C conform with this requirement, but Megamax
C, for example, does not. C programs have about 4 kb available for the stack.

Memo: The following was taken from the amiga version of the manual:

You may require an assembler interface like:

name:    movem.l a3-a6,regsave
         jsr     c_name
         movem.l regsave,a3-a6
         rts

regsave: ds.l    4

You may then need to employ an extra dummy parameter in your C routine, to
mask the return address of 'jsr c_name'. For example:

name (long x, long y)
c_name(long dummy, long x, long y)