From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-prs-return-12524-listarch-gcc-prs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 1782 invoked by alias); 7 Dec 2001 18:26:04 -0000
Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Archive: <http://gcc.gnu.org/ml/gcc-prs/>
List-Post: <mailto:gcc-prs@gcc.gnu.org>
List-Help: <mailto:gcc-prs-help@gcc.gnu.org>
Sender: gcc-prs-owner@gcc.gnu.org
Received: (qmail 1736 invoked by uid 71); 7 Dec 2001 18:26:02 -0000
Date: Fri, 07 Dec 2001 10:26:00 -0000
Message-ID: <20011207182602.1732.qmail@sources.redhat.com>
To: bkoz@gcc.gnu.org
Cc: gcc-prs@gcc.gnu.org,
From: Philip Martin <pmartin@uklinux.net>
Subject: Re: libstdc++/3720: Problems with num_get
Reply-To: Philip Martin <pmartin@uklinux.net>
X-SW-Source: 2001-12/txt/msg00432.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR libstdc++/3720; it has been noted by GNATS.

From: Philip Martin <pmartin@uklinux.net>
To: bkoz@gcc.gnu.org
Cc: gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
   schmid@snake.iap.physik.tu-darmstadt.de
Subject: Re: libstdc++/3720: Problems with num_get
Date: 07 Dec 2001 18:21:13 +0000

 bkoz@gcc.gnu.org writes:
 
 > Synopsis: Problems with num_get
 > 
 > State-Changed-From-To: analyzed->feedback
 > State-Changed-By: bkoz
 > State-Changed-When: Fri Dec  7 01:11:50 2001
 > State-Changed-Why:
 >     Try this:
 >     
 >     2001-12-06  Benjamin Kosnik  <bkoz@redhat.com>
 >     
 >             libstdc++/3720
 >             * include/bits/locale_facets.tcc (num_put): Clean.
 >             (num_get::_M_extract_float): Change argument to string. 
 >             (num_get::do_get(float)): Fixup.
 >             (num_get::do_get(double)): Same.
 >             (num_get::do_get(long double)): Same.
 >             (num_get::_M_extract_int): Add maximum length parameter, __max.
 >             (num_get::_M_extract_float): Correct zeros, use string.
 >             * include/bits/locale_facets.h (num_get::_M_extract_float): Change
 >             declaration here.
 >             * src/locale.cc (__num_base::_S_atoms): Remove x, X.
 >             * testsuite/27_io/istream_extractor_arith.cc (test13): Add.
 >             
 >     2001-12-06  Philip Martin  <pmartin@uklinux.net>
 >     
 >             * testsuite/27_io/istream_extractor_arith.cc    
 >     (test12): Add
 >             tests for excess input digits.
 >        
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&pr=3720&database=gcc
 
 
 1. Looking at the code, there are two calls to log() per integer
    input in _M_extract_int() in locale_facets.tcc
 
       // Figure out the maximum number of digits that can be extracted
       // for the given type, using the determined base.
       int __max_digits;
       if (__base != 10)
         __max_digits = static_cast<int>(ceil(__max * log(10.0)
                                            /log(static_cast<double>(__base))));
       else
         __max_digits = __max;
 
    All standard input is in base 8, 10, or 16, so how about something
    based on
 
        if (__base == 10)
          __max_digits = __max;
        else if (__base == 8)
          __max_digits = 1 + __max * 11073 / 10000; // approx. log(10)/log(8)
        else if (__base == 16)
          __max_digits = 1 + __max *  8305 / 10000; // approx. log(10)/log(16)
        else
          ???
 
    I haven't fully checked if this is accurate enough, however with
    the truncation to an int no great accuracy is required.
 
 
 2. You aren't calling test13() from main() in
    testsuite/27_io/istream_extractor_arith.cc
 
 
 3. Trying the code, input of std::numeric_limits<T>::max() in octal or
    hex doesn't appear to work for integers, e.g. reading 017777777777
    into a long on x86 doesn't work, it appears to accept one character
    too few. Decimal works.
 
 
 Philip