Date: Tue, 7 Mar 2000 22:22:04 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: cjclark@home.com Cc: bright@wintelcom.net (Alfred Perlstein), molter@csl.sri.com (Marco Molteni), freebsd-chat@FreeBSD.ORG Subject: Re: how to do this C preprocessor trick? Message-ID: <200003072222.PAA01371@usr09.primenet.com> In-Reply-To: <20000226003741.C20702@cc942873-a.ewndsr1.nj.home.com> from "Crist J. Clark" at Feb 26, 2000 12:37:41 AM
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> Why a,
>
> do { <stuff> } while(0)
>
> Rather than just,
>
> { <stuff> }
To make it anal.
It requires a semicolon in the first case.
In the second case, it can be expanded, e.g. in an "if/else" as
if( x)
{ <stuff> };
else
other_stuff...
as opposed to:
if( x)
do { <stuff> } while(0);
else
other_stuff...
Basically, it lets people be lazy about semicolongs and about
making macros upper case and functions lower case, so you can
tell if you are getting a function call overhead or an inline
preprocessor expansion of a macro.
I personally think it's lazy coding, and leads to bad practices,
like lowercase macro names or upper case function names becoming
an acceptable practice.
For blocks of code, it makes it real easy to include more than
the 10 lines of code allowed by the (L)GPL by innocently
including a header file, and not realizing that it's a block
macro instead of a simple macro, or that it's a macro instead
of a library function, etc..
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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