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Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle...

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle...
Date 2015-05-07 18:18 -0700
Organization None to speak of
Message-ID <87ioc3j29h.fsf@kst-u.example.com> (permalink)
References <a148e69a-0699-419d-ac3e-2fff86c8a158@googlegroups.com>

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G G <gdotone@gmail.com> writes:
> Could you please discuss whether casting a size_t variable
> to an unsigned variable the correct way to handle a warning
> I'm getting when I compile the program that follows.
>
> Inside the function mode(), rating is declared as a size_t variable.
> Ok, that makes sense to me because in the function, rating is
> is used as a subscript for an array. In order to capture the mode
> value, the author uses the variable rating and assigns it to
> modeValue which is declared as an unsigned int.

Surely you could have demonstrated the issue with a smaller program.

I don't get a warning with either version, but looking at the mode()
function:

> /************ mode() ************/
> void mode( unsigned int freq[], const unsigned int answer[] )
> {
>    size_t rating; 
[...]
>       if ( freq[ rating ] > largest ) 
>       {
>          largest = freq[ rating ];
>          modeValue = rating;
>       }
[...]
>    /* display mode value */
>    printf( "\nThe mode is the most frequent value.\n"
>            "For this run the mode is %u which occurred"
>           " %u times.\n", modeValue, largest );
> } 

the assignment

    modeValue = rating;

could lose information of rating exceeds UINT_MAX.

The obvious solution is to define modeValue as a size_t.  Like rating,
modeValue is an index into the array.

It might also be reasonable for both rating and modeValue to be of type
unsigned int *if* you can be sure that the array won't exceed UINT_MAX
elements.  But if you use size_t you don't have to worry about that.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... G G <gdotone@gmail.com> - 2015-05-07 17:12 -0700
  Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-07 18:18 -0700
    Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... G G <gdotone@gmail.com> - 2015-05-07 20:16 -0700
      Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... mark.bluemel@gmail.com - 2015-05-08 01:09 -0700
      Re: Could you please discuss whether casting a size_t variable to   unsigned int variable is the correct way to handle... Tim Prince <tprince@computer.org> - 2015-05-08 09:16 -0400
      Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-08 08:03 -0700
        Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-05-08 10:30 -0700
          Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... jadill33@gmail.com - 2015-05-08 11:12 -0700
          Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-08 11:22 -0700
            Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-08 18:42 +0000
          Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Bartc <bc@freeuk.com> - 2015-05-08 19:25 +0100
            Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Stephen Sprunk <stephen@sprunk.org> - 2015-05-08 15:12 -0500
              Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Bartc <bc@freeuk.com> - 2015-05-08 22:38 +0100
                Re: Could you please discuss whether casting a size_t variable to   unsigned int variable is the correct way to handle... Ian Collins <ian-news@hotmail.com> - 2015-05-09 11:01 +1200
        Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-10 09:19 -0700
          Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-10 11:26 -0700
            Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-11 21:31 -0700
              Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-12 05:50 +0000
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-12 10:05 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-12 11:10 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-12 12:59 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-22 08:11 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-22 11:20 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-24 07:59 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-24 13:44 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-12 11:09 -0700
              Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-05-12 11:02 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-22 08:01 -0700
            Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Waldek Hebisch <hebisch@antispam.uni.wroc.pl> - 2015-06-08 01:06 +0000
              Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-07 19:12 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... James Kuyper <jameskuyper@verizon.net> - 2015-06-08 11:28 -0400
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Waldek Hebisch <hebisch@antispam.uni.wroc.pl> - 2015-06-09 12:23 +0000
            Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-06-08 10:56 -0700
              Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-08 11:32 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Bartc <bc@freeuk.com> - 2015-06-08 19:40 +0100
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Richard Heathfield <rjh@cpax.org.uk> - 2015-06-08 20:03 +0100
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-08 13:43 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-06-08 21:03 +0000
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-08 14:52 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-06-09 08:30 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-06-09 16:48 +0100
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-09 08:55 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-06-10 10:09 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-10 11:05 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-06-11 11:04 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-06-11 11:31 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-06-11 13:49 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-06-12 09:00 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 07:25 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-07-11 10:04 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... James Kuyper <jameskuyper@verizon.net> - 2015-07-11 13:39 -0400
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 13:44 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Keith Thompson <kst-u@mib.org> - 2015-07-11 16:15 -0700
                Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... David Kleinecke <dkleinecke@gmail.com> - 2015-06-09 08:31 -0700
  Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-05-07 20:34 -0700
    Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... Richard Heathfield <rjh@cpax.org.uk> - 2015-05-08 09:48 +0100
  Re: Could you please discuss whether casting a size_t variable to unsigned int variable is the correct way to handle... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-08 05:12 +0000

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