Path: utzoo!attcan!uunet!husc6!mailrus!uflorida!gatech!udel!mmdf
From: iphwk%MTSUNIX1.BITNET@cunyvm.cuny.edu (Bill Kinnersley)
Newsgroups: comp.sys.amiga
Subject: Re: Re: Recognizing the break character
Message-ID: <3498@louie.udel.EDU>
Date: 26 Jul 88 20:14:25 GMT
Sender: mmdf@udel.EDU
Lines: 39

[In "Re: Recognizing the break character?", Wayne Young said:]
>
> If you look around in some of the earlier Fish disks, you'll find a little
> gem that Fred wrote himself.  It's a cc command for Lattice, and it comes
> with sources.  There's some code in it which checks for ^C, and you can
> easily extract the necessary stuff to make your own check_abort() routine.
> --
>        {uunet,utzoo,decvax,allegra}!utcsri!utflis!wayne
>
        Cc is on Fish Disks #2, 29 and 43.  I have #29, and what Fred is
doing is calling the Aztec Chk_Abort() function.  According to the manual,
Chk_Abort():

"aborts the program if (1) ^C has been typed and (2) the global short
Enable_Abort is non-zero (which it is by default).  If either of these
conditions isn't satisfied, Chk_Abort() simply returns."

Fred is using an undocumented (or underdocumented) feature, namely WHAT
it returns.  Chk_Abort() returns the result of SetSignal(0L,0x1000L), which
can be used as a Boolean to poll for ^C.

All this is related to the question I had about using an Exception Handler
to simulate a Unix signal catch.  I'd still like to see a solution that
does not involve polling (although I can see that polling is what you want
in some cases).  The problem is that the semantics are different.  A caught
Unix signal causes a longjmp, whereas an Amiga Exception is a rather
special form of subroutine call, and must return to the OS.


--

Bill Kinnersley
  Physics Department            BITNET: iphwk@mtsunix1
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"He learned to communicate with birds and discovered that their conversation
was fantastically boring.  It was all to do with wind speed, wingspan,
power-to-weight ratios and a fair bit about berries."