29 Jun
2021
29 Jun
'21
6:18 p.m.
Thanks Noel, Clem for your always generous and highly informative answers.
I'll digest that and enjoy using C routines in my assembly programs!
Paul
*Paul Riley*
Email: paul(a)rileyriot.com
On Tue, 29 Jun 2021 at 06:37, Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote:
From: Paul
Riley <paul(a)rileyriot.com>
> (I wrote a note, BITD, explaining how all
this worked; I'll upload
it
> to the CHWiki when I get a chance.)
Now here:
https://gunkies.org/wiki/PDP-11_C_stack_operation
along with simple examples of args and auto variables, which are both
referenced via the FP.
As a non-C consumer of printf, should I point R5
at some space for a
stack and call printf in the same manner as the C example I cited?
Not necessary to do anything with R5 (you can leave it blank); the only
things
a PDP-11 C routine needs are:
- a good stack
- the arguments, and return point, on the top of the stack
csv will set up the frame pointer, making no assumptions about the old
contents of R5 - see the source:
http://ana-3.lcs.mit.edu/~jnc/tech/unix/lib/csv.s
although it does save the old R5 contents, and restore them on exit.
Noel