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Groups > comp.lang.c > #21781

Re: Array sizes and const

From "BartC" <bc@freeuk.com>
Newsgroups comp.lang.c
Subject Re: Array sizes and const
Date 2012-06-04 00:23 +0100
Organization A noiseless patient Spider
Message-ID <jqgrmr$91a$1@dont-email.me> (permalink)
References (6 earlier) <a327a6F5maU3@mid.individual.net> <jqgpig$plu$1@dont-email.me> <a328b5F5maU4@mid.individual.net> <9aeb00b1-2fd5-4259-901b-54b6fbec8956@googlegroups.com> <a329evF5maU5@mid.individual.net>

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"Ian Collins" <ian-news@hotmail.com> wrote in message 
news:a329evF5maU5@mid.individual.net...
> On 06/ 4/12 11:04 AM, Malcolm McLean wrote:
>> בתאריך יום ראשון, 3 ביוני 2012 23:55:33 UTC+1, מאת Ian Collins:

>> But if it sends the triangle to the rendering hardware directly, the 
>> ENGINE *
>> is a const. If it buffers it, it is mutable.
>
> There's a good example of the confusion, does it modify the triangle or 
> not?  From the description you give, it looks like if does not in either 
> case.
>
> It is very much the callers business to know whether the triangle it 
> passes will or will not be molested by the function.  What if it has a 
> table of triangles in read only memory?
>
> The constness of the parameter has nothing to do with how the function 
> does its job.

Would a const attribute be any use here:

#include <stdio.h>
#include <string.h>

void changestr(char* s){
s[0]='?';
}

int main(void)
{
changestr("abcdef");
puts("abcdef");
}

I want to able to use changestr() to modify a string variable. But how can I 
stop a string literal being passed (which will either corrupt the literal, 
or will crash, on my tests)?

It's possible the new write-attribute I mentioned a couple of posts ago (eg. 
'var' to mean the opposite of 'const') could be useful here. Then the 
compiler knows passing the string literal is a mistake.

(And I can't find a gcc warning level to tell me that a string literal is 
being passed as a non-const char* parameter which could potentially 
overwrite it.)

-- 
Bartc 

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Thread

Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-02 15:43 -0500
  Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-03 08:56 +1200
  Re: Array sizes and const Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-02 16:59 -0400
    Re: Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-02 16:35 -0500
      Re: Array sizes and const jgk@panix.com (Joe keane) - 2012-06-08 20:05 +0000
      Re: Array sizes and const jgk@panix.com (Joe keane) - 2012-06-09 21:36 +0000
    Re: Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-02 16:43 -0500
  Re: Array sizes and const Keith Thompson <kst-u@mib.org> - 2012-06-02 14:59 -0700
    Re: Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-02 17:12 -0500
      Re: Array sizes and const Keith Thompson <kst-u@mib.org> - 2012-06-02 18:27 -0700
        Re: Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-02 22:27 -0500
      Re: Array sizes and const "BartC" <bc@freeuk.com> - 2012-06-03 11:24 +0100
        Re: Array sizes and const Keith Thompson <kst-u@mib.org> - 2012-06-03 13:51 -0700
          Re: Array sizes and const "BartC" <bc@freeuk.com> - 2012-06-04 12:20 +0100
            Re: Array sizes and const Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-04 13:54 +0200
            Re: Array sizes and const Keith Thompson <kst-u@mib.org> - 2012-06-04 14:32 -0700
  Re: Array sizes and const Nobody <nobody@nowhere.com> - 2012-06-02 23:50 +0100
    Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-03 10:53 +1200
      Re: Array sizes and const Nobody <nobody@nowhere.com> - 2012-06-03 14:35 +0100
    Re: Array sizes and const James Kuyper <jameskuyper@verizon.net> - 2012-06-02 21:11 -0400
      Re: Array sizes and const Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-03 07:39 -0700
        Re: Array sizes and const James Kuyper <jameskuyper@verizon.net> - 2012-06-03 16:03 -0400
        Re: Array sizes and const Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-03 21:49 +0100
          Re: Array sizes and const Keith Thompson <kst-u@mib.org> - 2012-06-03 14:49 -0700
          Re: Array sizes and const Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-03 15:02 -0700
            Re: Array sizes and const Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-04 01:21 +0100
        Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 09:08 +1200
          Re: Array sizes and const Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-03 15:08 -0700
            Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 10:37 +1200
              Re: Array sizes and const "BartC" <bc@freeuk.com> - 2012-06-03 23:47 +0100
                Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 10:55 +1200
                Re: Array sizes and const Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-03 16:04 -0700
                Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 11:14 +1200
                Re: Array sizes and const "BartC" <bc@freeuk.com> - 2012-06-04 00:23 +0100
                Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 11:30 +1200
                Re: Array sizes and const "BartC" <bc@freeuk.com> - 2012-06-04 00:52 +0100
                Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 12:04 +1200
                Re: Array sizes and const Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-04 01:39 +0100
                Re: Array sizes and const Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-04 02:35 -0700
                Re: Array sizes and const Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-04 01:33 +0100
                Re: Array sizes and const Ian Collins <ian-news@hotmail.com> - 2012-06-04 12:35 +1200
                Re: Array sizes and const pacman@kosh.dhis.org (Alan Curry) - 2012-06-04 21:28 +0000
        Re: Array sizes and const James Kuyper <jameskuyper@verizon.net> - 2012-06-04 12:08 -0400
        Re: Array sizes and const jgk@panix.com (Joe keane) - 2012-06-04 22:49 +0000
    Re: Array sizes and const David Brown <david.brown@hesbynett.no> - 2012-06-03 15:46 -0500
  Re: Array sizes and const Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-08 02:08 -0700
    Re: Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-08 06:45 -0500
      Re: Array sizes and const Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-08 10:49 -0700
        Re: Array sizes and const Les Cargill <lcargill99@comcast.com> - 2012-06-08 18:05 -0500
    Re: Array sizes and const Keith Thompson <kst-u@mib.org> - 2012-06-08 13:31 -0700
      Re: Array sizes and const Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-08 20:30 -0700

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