Date: Wed, 9 Nov 2005 10:57:59 +1100
From: David Gibson <dwg@au1.ibm.com>
To: linas <linas@austin.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, linuxppc64-dev@ozlabs.org,
       linux-pci@atrey.karlin.mff.cuni.cz, linux-kernel@vger.kernel.org,
       bluesmoke-devel@lists.sourceforge.net
Subject: Re: typedefs and structs
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On Tue, Nov 08, 2005 at 05:23:27PM -0600, Linas Vepstas wrote:
> On Mon, Nov 07, 2005 at 08:11:13PM -0500, Steven Rostedt was heard to remark:
> > On Mon, 2005-11-07 at 14:41 -0600, linas wrote:
> > 
> > don't use typedef to get rid of "struct".
> > 
> > This was for the simple reason, too many developers were passing
> > structures by value instead of by reference, just because they were
> > using a type that they didn't realize was a structure. 
> 
> That's a rather bizarre mistake to make, since, in order to 
> access a values in such a beast, you have to use a dot . instead 
> of an arrow -> and so it hits ou in the face that you passed a value
> instead of a reference.
> 
> ----
> Off-topic: There's actually a neat little trick in C++ that can 
> help avoid accidentally passing null pointers.  One can declare 
> function declarations as:
> 
>   int func (sturct blah &v) {
>     v.a ++; 
>     return v.b;
>   }
> 
> The ampersand says "pass argument by reference (so as to get arg passing
> efficiency) but force coder to write code as if they were passing by value"
> As a result, it gets difficult to pass null pointers (for reasons
> similar to the difficulty of passing null pointers in Java (and yes,
> I loathe Java, sorry to subject you to that))  Anyway, that's a C++ trick 
> only; I wish it was in C so I could experiment more and find out if I 
> like it or hate it.

I hate it: it obscures the fact that it's a pass-by-reference at the
callsite, which is useful information.  Although this is, admittedly,
the least confusing use of C++ reference types.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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