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From: kaz@cadovax.UUCP (Kerry Zimmerman)
Newsgroups: comp.sys.amiga
Subject: Printer drivers and Aztec 3.04a
Message-ID: <1522@cadovax.UUCP>
Date: Mon, 4-May-87 15:57:13 EDT
Article-I.D.: cadovax.1522
Posted: Mon May  4 15:57:13 1987
Date-Received: Wed, 6-May-87 04:47:27 EDT
Reply-To: kaz@cadovax.UUCP (Kerry Zimmerman)
Organization: Contel Business Systems, Torrance, CA
Lines: 32
Keywords: Aztec 3.04a Printer Driver
Summary: Problem with compiler not preserving register A6

[]

I ran into a problem this weekend converting an Epson LQ800
printer driver to Manx Aztec 3.04a.  I have read the recent notes
posted by others describing their efforts in this area.  No one
seems to have mentioned what I ran into.

I compiled the driver with no problem using the +BCD compiler options 
and linked it with the cl32.lib.  The driver worked fine until graphic 
printing was finished, at which point the system GURUed.

I eventually isolated the problem by using the +AT option to get
the assembly source for render.c.  What I determined (using DB)
was that register A6 is used by render, but not saved and restored
before and after the routine.  As a result, the printer.device who
calls render, and who expected A6 to be preserved, crashed. 

I solved the problem (with a bandaid) by adding some assembly code
to save and restore A6 at the entrance and exit of render.

My question is shouldn't A6 have been protected automatically by
the compiler?  The compiler does preserve D2 and D3, why not A6?
Is there another option I should have used?  Is there anyway to
make A6 be the frame pointer (like in lattice) instead of A5?
This seems necessary since the printer.device was probably created
with lattice, and assumes A6 will be the frame pointer.

Thanks for any help.

Kerry Zimmerman
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