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From: niklas@appli.se (Niklas Hallqvist)
Newsgroups: comp.lang.c++
Subject: Re: references as class member variables
Message-ID: <1391@appli.se>
Date: 3 Jun 91 10:31:52 GMT
References: <9105300036.aa15925@ics.uci.edu>
Organization: Applitron Datasystem AB, GOTHENBURG, SWEDEN
Lines: 41

schmidt@crimee.ics.uci.edu (Douglas C. Schmidt) writes:

>Hi,

>	I'm curious...  Does anyone know what the "proper" output for
>the following program should be (or is it perhaps officially undefined?)
>g++ prints 10, 11, whereas cfront 2.0 prints 11, 11.

>--------------------------------------
>struct Foo
>{
>  int &r;

>  Foo (int s): r (s) { }
>};

>extern "C" void printf (const char *, ...);

>main ()
>{
>  Foo f (10);
>  Foo g (11);

>  printf ("%d, %d\n", f.r, g.r);
>}
>----------------------------------------

I don't have my ARM with me, but as I recall it, this is officially
undefined.  You are aliasing a parameter passed by value, which is
risky, at least.  If the parameter is passed in a register, the compiler
is allowed to make a temporary which is then aliased.  If it's
passed in a stack slot, the stack slot will be aliased.  This stack
slot could of course be reused when it goes out of scope.  If this is
incorrect, please flame me ;->

						Niklas
-- 
Niklas Hallqvist	Phone: +46-(0)31-40 75 00
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