NetNews Usenet Archive 1992 #19/NN_1992_19.iso/spool/comp/lang/cplus/13020

Text File | 1992-08-29 | 1.5 KB | 39 lines

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From: [e-mail] (Andrew Koenig)
Newsgroups: comp.lang.c++
Subject: Re: complex classes and temporary destruction.
Message-ID: <[e-mail]>
Date: 28 Aug 92 15:33:09 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Reply-To: [e-mail] ()
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 27

In article <[e-mail]> [e-mail] (Mark Christian Barnes) writes:

>  Have the temporary "inherit" (for lack of a better word) the
> storage class of p. If p is an auto variable then 's+t' should
> be auto too. Destroy p and 's+t' together. If p is static, then
> perhaps have 's+t' be static as well, onc instance of 's+t'
> gets re-used each time the statement is executed.

I'm afraid that wouldn't work.  Consider this:

    char* I(char* x) { return x; }

The function I (for identity) just returns its argument, but to make things
difficult, it is compiled separately.  Now, you would like

    char* p = s+t;

to cause the temporary for s+t to stick around as long as p does,
but what are you going to do about this?

    char* p = I(s+t);

There's no way to know what I() does, so what basis do you have for
letting the lifetime of p affect that of s+t?
--
                --Andrew Koenig
                  [e-mail]