RE: libstdc++/6360: Wrong workaround in char_traits.h - ignore stops on \0xff

RE: libstdc++/6360: Wrong workaround in char_traits.h - ignore stops on \0xff

[Mads]

The following reply was made to PR libstdc++/6360; it has been noted by GNATS.

From: "Mads" <mki@maconomy.dk>
To: <gcc-gnats@gcc.gnu.org>,
	<nobody@gcc.gnu.org>
Cc:  
Subject: RE: libstdc++/6360: Wrong workaround in char_traits.h - ignore stops on \0xff
Date: Thu, 18 Apr 2002 17:23:33 +0200

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 I tried to attach the attached file to the bugreport - but failed.
 
 Can it be submitted this way?
 
 /Mads
 
 > -----Original Message-----
 > From: gcc-gnats@gcc.gnu.org [mailto:gcc-gnats@gcc.gnu.org]
 > Sent: Thursday, April 18, 2002 5:06 PM
 > To: mki@maconomy.dk
 > Subject: Re: libstdc++/6360: Wrong workaround in 
 > char_traits.h - ignore
 > stops on \0xff
 > 
 > 
 > Thank you very much for your problem report.
 > It has the internal identification `libstdc++/6360'.
 > The individual assigned to look at your
 > report is: unassigned. 
 > 
 > >Category:       libstdc++
 > >Responsible:    unassigned
 > >Synopsis:       Wrong workaround in char_traits.h - ignore 
 > stops on \0xff
 > >Arrival-Date:   Thu Apr 18 08:06:00 PDT 2002
 > 
 
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 	name="IstreamIgnore.cpp"
 Content-Transfer-Encoding: quoted-printable
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 	filename="IstreamIgnore.cpp"
 
 #include <iostream>=0A=
 #include <sstream>=0A=
 =0A=
 using namespace std;=0A=
 =0A=
 int main()=0A=
 {=0A=
   stringstream ss("abcd" "\xFF" "1234abcd");=0A=
 =0A=
   char c;=0A=
   ss >> c;=0A=
   cout << "1st char is: " << c << endl;=0A=
 =0A=
   cout << "Skipping 8 chars (i.e. until after the digits)..." << endl;=0A=
   ss.ignore(8);=0A=
 =0A=
   cout << "The rest of the stream contains: '" << ss.rdbuf() << '\'' << =
 endl;=0A=
 =0A=
   return 0;=0A=
 }=0A=
 
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Re: libstdc++/6360: Wrong workaround in char_traits.h - ignore stops on \0xff

[bkoz]

Synopsis: Wrong workaround in char_traits.h - ignore stops on \0xff

Responsible-Changed-From-To: unassigned->bkoz
Responsible-Changed-By: bkoz
Responsible-Changed-When: Mon Apr 22 13:31:19 2002
Responsible-Changed-Why:
    Mine.
State-Changed-From-To: analyzed->closed
State-Changed-By: bkoz
State-Changed-When: Mon Apr 22 13:31:19 2002
State-Changed-Why:
    Fixed.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6360

Re: libstdc++/6360: Wrong workaround in char_traits.h - ignore stops on \0xff

[bkoz]

Synopsis: Wrong workaround in char_traits.h - ignore stops on \0xff

State-Changed-From-To: open->analyzed
State-Changed-By: bkoz
State-Changed-When: Fri Apr 19 12:28:52 2002
State-Changed-Why:
    confirmed on 3.1, 3.2 sources
    
    // 2002-04-19 PR libstdc++ 6360
    #include <sstream>
    using namespace std;
     
    int main()
    {
      bool test = true;
      stringstream ss("abcd" "\xFF" "1234ina donna coolbrith");
      
      char c;
      ss >> c;
      test &= c == 'a';
      ss.ignore(8);
      ss >> c;
      test &= c == 'i';  
      
      return 0;
    }
    

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6360

libstdc++/6360: Wrong workaround in char_traits.h - ignore stops on \0xff

[mki]

>Number:         6360
>Category:       libstdc++
>Synopsis:       Wrong workaround in char_traits.h - ignore stops on \0xff
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 18 08:06:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Mads Kiilerich
>Release:        3.0.4
>Organization:
>Environment:
Seen on RedHat linux 6.2 - and on Solaris 2.7
>Description:
The default delimiter for Istream::ignore is EOF (-1).

Several places in include/g++-v3/bits/istream.tcc the following is found:

    const int_type __idelim = traits_type::to_int_type(__delim);

calling the method in gcc/include/g++-v3/bits/char_traits.h:184 :

        // To keep both the byte 0xff and the eof symbol 0xffffffff
        // from ending up as 0xffffffff.
        static int_type
        to_int_type(const char_type& __c)
        { return static_cast<int_type>(static_cast<unsigned char>(__c)); }

- but then __idelim is set to 255, causing Istream::ignore to stop ignoring first time it meets a char value of 255.

In this case the delimiter should be -1, so that ignorance only stops when a real negative unsigned char is found - and that hardly happens...
>How-To-Repeat:
The following testcase is expected to do as it does when compiled with KAI:

[mk@linux-tools IstreamIgnore]$ ./IstreamIgnore.KCC
1st char is: a
Skipping 8 chars (i.e. until after the digits)...
The rest of the stream contains: 'abcd'

But using gcc 3.0.4 we get:

[mk@linux-tools IstreamIgnore]$ ./IstreamIgnore.gcc
1st char is: a
Skipping 8 chars (i.e. until after the digits)...
The rest of the stream contains: '1234abcd'
>Fix:
Idunno. But the current workaround does not seem good...
>Release-Note:
>Audit-Trail:
>Unformatted: