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From: en2j@vax1.UUCP (Thomas Purcell)
Newsgroups: comp.lang.c
Subject: explicit runtime condition code checking, particularly overflow
Message-ID: <574@vax1.UUCP>
Date: Wed, 2-Dec-87 11:03:31 EST
Article-I.D.: vax1.574
Posted: Wed Dec  2 11:03:31 1987
Date-Received: Sat, 5-Dec-87 14:46:52 EST
Expires: Thu, 31-Dec-87 00:00:00 EST
Reply-To: en2j@vax1.ccs.cornell.edu
Organization: Cornell Computer Services, Ithaca NY
Lines: 22
Keywords: runtime condition condition_code checking overflow
Summary: would like to know how to essentially do a "branch on overflow"


I'd love to know if there's ANY way of doing runtime condition code checking
in C.  In particular, I'd like to know if there's any way to write a line of
C code which essentially translates into a Branch On Overflow, or Bcc LABEL, 
where B means branch, cc is a condition code, and label is the name of a 
procedure.

Kernighan and Ritchie I think say something like 'there should be a library
routine to deal with it, depending on your machine'.  My other two C
manuals, (Thom Hogan, and the other by Steve Kochan) don't seem to mention
the problem at all.  [perhaps I missed a mention of it]

All I want to do is see if an expression which I'm evaluating overflows, and
handle it myself if it does!  And the only answer I've gotten so far is
on the order of "random machine action on overflow depending on
implementation."  Can anybody help?

Please send a copy of your response directly.

-thomas
en2j@crnlvax1.bitnet		The symbol after the "vax" is a ONE, not
en2j@vax1.ccs.cornell.edu			an L .