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From: chris@mimsy.umd.edu (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: compiler detecting divide by zero
Message-ID: <28079@mimsy.umd.edu>
Date: 29 Nov 90 08:22:50 GMT
References: <36233@cup.portal.com> <5857@stpstn.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26

In article <5857@stpstn.UUCP> lerman@stpstn.UUCP (Ken Lerman) writes:
>I haven't tried it, but I'll bet that:
>    int divide(int a, int b){ return a/b; }
>will cause your divide error when called by:
>    x = divide(1,0);
>Of course, if your compiler is brilliant, you might have to put the
>function divide in a separate file. :-)

Even that is unlikely to help for long.  (You can expect better IBM PC
compilers to do cross-module optimization within 5 years.  [I actually
expect it sooner than this.  MIPS and Sun already do it.])

Here is something that *will* (must) work:

	const volatile int zero = 0;
	int exception = 1 / zero;

A compiler cannot assume that a `const volatile int' has any particular
value.  For instance:

	extern const volatile int clock;	/* mapped by linker to clock */

might tell you the current time in seconds since the machine was booted.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 405 2750)
Domain:	chris@cs.umd.edu	Path:	uunet!mimsy!chris