From owner-freebsd-hackers  Thu Jun  4 23:18:36 1998
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Date: Thu, 4 Jun 1998 23:16:11 -0700 (PDT)
From: Julian Elischer <julian@whistle.com>
To: Chris Csanady <cc@swing.ca.sandia.gov>
cc: freebsd-hackers@FreeBSD.ORG
Subject: Re: style(9) error?
In-Reply-To: <199806042122.QAA00625@swing.ca.sandia.gov>
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not th econditional part, the THEN clause..

e.g.
if (condition)
	MACRO(x);
else
	MACRO2(y);

evaluates correctly to:


if (condition)
	do {
		sdfdfsg;
		sdfghdghh;
	} while (0);
 else
	do {
		ffdgdfsgs;
		sdfgsdfgsIdg;
	} while (0);


which is what you require, 

Hopefully the compiler will remove the un-needed loping code.
(certainly it will since this is so commmon.)


julian



On Thu, 4 Jun 1998, Chris Csanady wrote:

> 
> I would like to make use of a feature that style tells me I can use, but
> gcc tells me I can not..
> 
> From style(9):
> 
>      es, it makes it easier to read.  If the macro encapsulates a compound
>      statement, enclose it in a ``do'' loop, so that it can safely be used in
>      ``if'' statements.  Any final statement-terminating semicolon should be
>      supplied by the macro invocation rather than the macro, to make parsing
>      easier for pretty-printers and editors.
> 
>      #define MACRO(x, y) do {                                                \
>              variable = (x) + (y);                                           \
>              (y) += 2;                                                       \
>      } while(0)
> 
> As far as I can tell, it is impossible to put a do loop in a if statement,
> or anything else.  Is this correct?  I always thought that blocks evaluated
> to their last statements, but it seems not..
> 
> Chris Csanady
> 
> 
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