Re: Right trim string function in C

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: Right trim string function in C
Date	2012-02-11 12:06 -0800
Organization	None to speak of
Message-ID	<lnzkcpjfse.fsf@nuthaus.mib.org> (permalink)
References	(2 earlier) <op.v9hajzxp5qv6o3@toshiba-laptop> <trim-20120210205032@ram.dialup.fu-berlin.de> <trim-20120210210617@ram.dialup.fu-berlin.de> <0.6430c14d237a7d688fd1.20120210215638GMT.87pqdmbbe1.fsf@bsb.me.uk> <isspace-20120211201630@ram.dialup.fu-berlin.de>

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ram@zedat.fu-berlin.de (Stefan Ram) writes:
> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>>In addition to being careful about the pointers, you need to finesse the
>>mess that is isspace (and friends) when char might be signed.  
>
>   Ok, I admit that I do not understand this. After
>
> #include <ctype.h>
>
>   , and in the scope of something like
>
> char c;
>
>   , the expression
>
> isspace( c )
>
>   will be nonzero, when c is a standard white-space character
>   (or is one of a locale-specific set of characters).
>
>   Where is the problem Ben refers to?

N1570 7.4p1:

    ... the argument is an int, the value of which shall be
    representable as an unsigned char or shall equal the value of
    the macro EOF. If the argument has any other value, the behavior
    is undefined.

If plain char is signed and the value of c is negative (and not
equal to EOF), then the behavior of isspace(c) is undefined.

This can be avoided by writing:

    isspace((unsigned char)c)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

Right trim string function in C peter <pc722@nospam.mail.com.br> - 2012-02-10 18:17 +0000
  Re: Right trim string function in C James Kuyper <jameskuyper@verizon.net> - 2012-02-10 13:36 -0500
    Re: Right trim string function in C Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-10 11:00 -0800
      Re: Right trim string function in C "BartC" <bc@freeuk.com> - 2012-02-14 12:41 +0000
        Re: Right trim string function in C "BartC" <bc@freeuk.com> - 2012-02-14 14:14 +0000
          Re: Right trim string function in C Ike Naar <ike@iceland.freeshell.org> - 2012-02-15 00:03 +0000
            Re: Right trim string function in C "BartC" <bc@freeuk.com> - 2012-02-15 01:00 +0000
              Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-15 02:08 +0000
              Re: Right trim string function in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-15 03:08 -0800
                Re: Right trim string function in C gazelle@shell.xmission.com (Kenny McCormack) - 2012-02-15 13:00 +0000
                Re: Right trim string function in C Kaz Kylheku <kaz@kylheku.com> - 2012-02-16 00:36 +0000
              Re: Right trim string function in C Kaz Kylheku <kaz@kylheku.com> - 2012-02-16 00:28 +0000
              Re: Right trim string function in C gordonb.7bjv1@burditt.org (Gordon Burditt) - 2012-03-12 03:27 -0500
                Re: Right trim string function in C China Blue Water Navy <chine.bleu@yahoo.com> - 2012-03-12 03:57 -0800
        Re: Right trim string function in C Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-14 09:59 -0800
      Re: Right trim string function in C Kaz Kylheku <kaz@kylheku.com> - 2012-02-14 12:56 +0000
        Re: Right trim string function in C Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-14 09:17 -0800
        Re: Right trim string function in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-14 10:10 -0800
  Re: Right trim string function in C Barry Schwarz <schwarzb@dqel.com> - 2012-02-10 11:30 -0800
    Re: Right trim string function in C James Kuyper <jameskuyper@verizon.net> - 2012-02-10 14:45 -0500
      Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-10 22:15 +0000
        Re: Right trim string function in C James Kuyper <jameskuyper@verizon.net> - 2012-02-10 17:21 -0500
          Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-10 23:25 +0000
          Re: Right trim string function in C Keith Thompson <kst-u@mib.org> - 2012-02-10 15:31 -0800
      Re: Right trim string function in C pete <pfiland@mindspring.com> - 2012-02-10 17:17 -0500
        Re: Right trim string function in C Devil with the China Blue Dress <chine.bleu@yahoo.com> - 2012-02-10 15:12 -0800
  Re: Right trim string function in C "Morris Keesan" <mkeesan@post.harvard.edu> - 2012-02-10 14:46 -0500
    Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-10 21:56 +0000
      Re: Right trim string function in C James Kuyper <jameskuyper@verizon.net> - 2012-02-10 17:08 -0500
        Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-10 23:14 +0000
          Re: Right trim string function in C David Thompson <dave.thompson2@verizon.net> - 2012-02-18 23:11 -0500
      Re: Right trim string function in C Keith Thompson <kst-u@mib.org> - 2012-02-11 12:06 -0800
      Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 20:12 +0000
      Re: Right trim string function in C Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-08 13:10 -0800
  Re: Right trim string function in C "Scott Fluhrer" <sfluhrer@ix.netcom.com> - 2012-02-10 15:39 -0500
  Re: Right trim string function in C Shao Miller <sha0.miller@gmail.com> - 2012-02-11 03:52 -0500
    Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 13:50 +0000
      Re: Right trim string function in C Shao Miller <sha0.miller@gmail.com> - 2012-02-11 11:47 -0500
        Re: Right trim string function in C Shao Miller <sha0.miller@gmail.com> - 2012-02-11 12:20 -0500
        Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 20:57 +0000
          Re: Right trim string function in C Shao Miller <sha0.miller@gmail.com> - 2012-02-11 17:43 -0500
  Re: Right trim string function in C Willem <willem@toad.stack.nl> - 2012-02-11 11:57 +0000
    Re: Right trim string function in C Willem <willem@toad.stack.nl> - 2012-02-11 18:11 +0000
  Re: Right trim string function in C August Karlstrom <fusionfile@gmail.com> - 2012-02-11 18:41 +0100
    Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 19:58 +0000
      Re: Right trim string function in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-11 13:11 -0800
      Re: Right trim string function in C August Karlstrom <fusionfile@gmail.com> - 2012-02-11 22:18 +0100
        Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-11 23:48 +0000
          Re: Right trim string function in C August Karlstrom <fusionfile@gmail.com> - 2012-02-12 02:20 +0100
          Re: Right trim string function in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-12 03:44 -0800
            Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-12 14:01 +0000
              Re: Right trim string function in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-12 11:06 -0800
                Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-12 19:34 +0000
                Re: Right trim string function in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-02-12 23:35 +0000
    Re: Right trim string function in C Barry Schwarz <schwarzb@dqel.com> - 2012-02-11 14:27 -0800
      Re: Right trim string function in C August Karlstrom <fusionfile@gmail.com> - 2012-02-12 14:40 +0100

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