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Date: Wed, 18 Sep 2002 01:46:00 -0000
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From: Andreas Schwab <schwab@suse.de>
Subject: Re: libstdc++/7961: compare( char *) implemented incorrectly.
Reply-To: Andreas Schwab <schwab@suse.de>
X-SW-Source: 2002-09/txt/msg00543.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR libstdc++/7961; it has been noted by GNATS.

From: Andreas Schwab <schwab@suse.de>
To: john.carter@tait.co.nz
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: libstdc++/7961: compare( char *) implemented incorrectly.
Date: Wed, 18 Sep 2002 10:39:54 +0200

 john.carter@tait.co.nz writes:
 
 |> A correct implementation would be...
 |>   template<typename _CharT, typename _Traits, typename _Alloc>
 |>     int
 |>     basic_string<_CharT, _Traits, _Alloc>::
 |>     compare(const _CharT* __s) const
 |>     {
 |>       size_type __size = this->size();
 |>       size_type __s_size = traits_types::length(__s);
 |>       size_type __min = __size;
 |>       if ( __size  > __s_size) 
 |>         __min = __s_size;
 |> 
 |>       int __r = traits_type::compare(_M_data(), __s, __min);
 |>       if (!__r)
 |> 	__r = __size - _s_size;
 |>        
 |>       return __r;
 |>     }
 
 This is not correct either, because __size - __s_size may overflow the
 range of int.  Try this instead:
 
       if (!__r)
 	__r = (__size > __s_size) - (__size < __s_size);
 
 Andreas.
 
 -- 
 Andreas Schwab, SuSE Labs, schwab@suse.de
 SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 Nürnberg
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