Path: utzoo!attcan!uunet!mcvax!ukc!strath-cs!glasgow!orr
From: orr@cs.glasgow.ac.uk (Fraser Orr)
Newsgroups: comp.lang.c++
Subject: Re: goodbye cpp ??? (macros vs. inline functions)
Keywords: cpp inline functions
Message-ID: <1931@crete.cs.glasgow.ac.uk>
Date: 23 Nov 88 18:13:44 GMT
References: <6590072@hplsla.HP.COM> <1757@dataio.Data-IO.COM> <3637@pt.cs.cmu.edu>
Reply-To: orr@cs.glasgow.ac.uk (Fraser Orr)
Organization: Comp Sci, Glasgow Univ, Scotland
Lines: 50

In article <3637@pt.cs.cmu.edu> agn@unh.cs.cmu.edu (Andreas Nowatzyk) writes:
>Bjarne Strousrup's C++ book claims that inline functions
>eliminate the need for most uses of macros and other
>cpp-features. I find that statement overly optimistic and
>plain false in many actual cases. Using the ATT version 1.2.1
>of C++, I found inline functions to be inadequate because:
>
Summary of critisims -
 a) Produce poor code
 b) Produce large numbers of temporary variables
 c) They have a lot of restrictions (loops etc)
 d) Lack control of instansiation
 e) There is no reasonalble substitute for conditional compilation.

Firstly, it seems points a) and b) are a fair critisism of
the compilers that we have at present. I would just say,
write a better compiler.

Restrictions - There are some unfortunate restrictions,
and there is no easy solution to this. But then again,
I never could write recursive macros anyway so its no
great loss to me.

Lack of control of instansiation, I don't see where the problem could
be.  The whole point of inline functions is that they should be
semantically identical to a function call.  I'd be interested to see an
example of this problem.

There is a reasonable substitute for conditional compilation,
its called modularisation. You write a system dependent file
for each system, and then link the appropriate one to a file
called "sys_depends.h". Simple, eh? What about if I want
one of my functions to do this for system A and that for system
B, you may ask. Simple, you write two functions, one for each system.
This might require you to have something like

SYS5= ...
BSD= ...
VMS= ...
SYSDEPENDS = SYS5

in your makefile, and you have to edit a line of it - big deal!
In fact with all these configure programs that seem to be distributed
with sources these days, you probably wouldn't even have to do that.

>   --  Andreas Nowatzyk  (DC5ZV)

==Fraser Orr ( Dept C.S., Univ. Glasgow, Glasgow, G12 8QQ, UK)
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