Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!cs.utexas.edu!uwm.edu!ogicse!ucsd!ames!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: SIGFPE signal problem
Message-ID: <12383@smoke.BRL.MIL>
Date: 19 Mar 90 23:30:05 GMT
References: <5450@rouge.usl.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 21

In article <5450@rouge.usl.edu> pcb@gator.cacs.usl.edu (Peter C. Bahrs) writes:
>I am trying to detect overflow, 0 divide and, although it may seem
>unlikely, underflow.  Doesn't SIGFPE detect this?

SIGFPE is a signal that may (or may not, depending on the system) be
generated upon floating-point exception.  Most UNIX-based C
implementations will generate SIGFPE upon division by zero, some of
them upon other forms of overflow, but few of them upon underflow.
Some implementations generate no SIGFPE at all, e.g. Gould UTX-32,
whose hardware couples integer and floating exceptions and which
relies on benign integer overflow (so it must disable all arithmetic
exceptions, alas).

Some vendors provide ways for your program to control behavior upon
exception, e.g. #pragma, compiler option, or mode-setting library
function.

>a = 999999999999999999999999999999999999999999999999999999999999999999999999999999999.9;

This would be much more likely to generate a compile-time diagnostic
than a run-time overflow exception.