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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Behaviour of setjmp/longjmp and registers
Message-ID: <15559@mimsy.UUCP>
Date: 20 Jan 89 21:11:21 GMT
References: <25@torsqnt.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 21

In article <25@torsqnt.UUCP> david@torsqnt.UUCP (David Haynes) writes:
>What should be the result of running the following program?

[example of register variables and longjmp deleted]

>Sequent, Ultrix and Vax C give results of j = 1, j = 4.
>Gcc gives a result of j = 1, j = 1.
>What does the ANSI standard say about this?

The ANSI standard says that register variables, like all other
automatic variables, must be declared `volatile' for you to be able to
assume the output will be `j = 1, j = 4'.  Of course, since there is no
`volatile' qualifier in most existing C compilers, in practise this
means that you must not declare variables as register in order to count
on them (so that `#define volatile /*empty*/' will work).

(I guess you were not reading when I posted this the last two or three
times last month. . . .)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris