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Path: utzoo!utcsri!greg
From: greg@utcsri.UUCP (Gregory Smith)
Newsgroups: net.lang.c
Subject: Re: sizeof "string"?  multi-line macro usage?
Message-ID: <3098@utcsri.UUCP>
Date: Sun, 13-Jul-86 14:53:45 EDT
Article-I.D.: utcsri.3098
Posted: Sun Jul 13 14:53:45 1986
Date-Received: Sun, 13-Jul-86 15:03:09 EDT
References: <343@vu-vlsi.UUCP>
Reply-To: greg@utcsri.UUCP (Gregory Smith)
Organization: CSRI, University of Toronto
Lines: 65
Summary: 

In article <343@vu-vlsi.UUCP> colin@vu-vlsi.UUCP writes:
>Question 1.
>
>Is it (portably) legal for sizeof to operate on a string constant?  I
>checked K&R, and they seem to have nothing to say about the subject.
..
>This came up because I have coded
>
>#define PROMPT "prog> "
>
>in an include file, and then later used 
>
>for (i = 0; i < sizeof(PROMPT) - 1; i++)	/* indent to first char of input */
>	putchar(' ');
>
>to get the proper indentation for error messages.  This worked great when
>compiled on Pyramid C, VAX VMS C, and Lattice C on a PC.  Then I ran into the
>Regulus C compiler (Regulus 4.2C) which is truly brain-damaged in many
>respects; as far as I can tell, its sizeof returns a random value when given
>a string.

Regulus is screwed up.
BTW,
	printf( "%*s",sizeof(PROMPT)-1, " ");
will work except that Regulus may not support * in formats.
Or if you want to get really efficient at the expense of weirdness:

	printf( "                    "+20-( sizeof(PROMPT)-1 ) );

>So is it just Regulus that's screwed up, or do I have to explicitly
>declare
>
>char prompt[] = PROMPT;
>
>and then take sizeof(prompt)?  (The latter _does_ work in Regulus.)
>
Interestingly, using PCC, sizeof("foobar") gives 7 but stuffs the string
"foobar" into memory which will never be used, so you may as well use the
prompt[] solution above. This may depend on the dialect of PCC you are using,
but all of ours do, and so does cc11 (PDP11). Dem bugs, dem bugs....

>
>Question 2.
>
>Does ANSI say anything about macro usage spanning more than one line?  Lattice
>C has something like
>
>#define max(a,b) ((a > b) ? a : b)
>
>but then barfs when I use the macro over more than one line, like
>
>x = min(very-long-expression-here,
>	another-very-long-expression-here);
>
>All the other compilers I've used have no trouble with this.  (By not allowing
>multi-line macro usage, Lattice is screwing with the usually transparent
>interchangeability of functions and macros...)
>
This is #definitely a preprocessor bug.

-- 
"You'll need more than a Tylenol if you don't tell me where my father is!"
						- The Ice Pirates
----------------------------------------------------------------------
Greg Smith     University of Toronto      UUCP: ..utzoo!utcsri!greg