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Path: utzoo!linus!security!genrad!decvax!duke!phs!smh@mit-eddie.UUCP (Steven M. Haflich)
From: smh@mit-eddie.UUCP
Newsgroups: net.lang.c
Subject: Re: Is this legal C?
Message-ID: <951@mit-eddi.UUCP>
Date: Wed, 23-Nov-83 07:25:42 EST
Article-I.D.: mit-eddi.951
Posted: Wed Nov 23 07:25:42 1983
Date-Received: Sun, 27-Nov-83 03:34:34 EST
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Path:duke!decvax!genrad!mit-eddie!smh
Message-ID:<951@mit-eddie.UUCP>
Date:Wed, 23-Nov-83 07:25:42 EST
Organization:MIT, Cambridge, MA

A minor quibble with Jerry Leichter, who writes:
---------------------------------------------
Consider setjmp/longjmp.  The standard way to use them is:

	if (setjmp(&buf) == 0)
	{	do something	}
	else
	{	handle the low-level error	}

This has the same control-passing structure as your goto example, once
the stack has been unwound.  Now, setjmp/longjmp are not part of the
language; but they have become pretty universal, and any compiler that
made them unimplementable would likely not gain much of a following.
---------------------------------------------
To the compiler there is a significant difference between a label on
an `if' conditional and the `setjmp' function call.  The former
requires the compiler generate code (if only an assembler label) while
the latter is a function which `magically' bashes -- whoops, I mean
restores -- the stack environment identically when `longjmp' is later
called.  `setjmp' is part of the object library environment, not the
language, and it would be incorrect for any C *compiler* to treat it
specially.

Steve Haflich, MIT Experimental Music Studio