Is this legal C?

smh at mit-eddie.UUCP smh at mit-eddie.UUCP
Wed Nov 23 22:25:42 AEST 1983

References: utcsrgv.2783 <2454 at yale-com.UUCP>
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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	}
	{	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

Steve Haflich, MIT Experimental Music Studio

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