Very serious bug...

[Theodore Papadopoulo <Theodore dot Papadopoulo at sophia dot inria dot fr>]

	Hi,

libstdc++-v3 (mainline, I do not know about the branch) is badly 
broken. The simple program:

#include <iostream>

int
main()
{
    char buffer[256];
    std::cin >> buffer; //    Why does nothing is read here !!!! (TO).
    std::cout << "Read: " << buffer << std::endl;
}

reads nothing:

vanuatu->g++ -v
Reading specs from /net/home/robotvis/gnu/gcc/lib/gcc-lib/i686-pc-linux-gnu/3.1/specs
Configured with: ../../Cvs/gcc/configure --with-gnu-as --with-gnu-ld --with-as=/net/home/robotvis/gnu/binutils/bin/as --with-ld=/net/home/robotvis/gnu/binutils/bin/ld --prefix=/net/home/robotvis/gnu/gcc
gcc version 3.1 20010228 (experimental)

vanuatu->g++ -g Test1.C
vanuatu->./a.out
fjkhvfdjhfdjkd
Read: 

It looks like this is related to an int/unsigned problem as in:

2001-03-02  Peter Schmid  <schmid@snake.iap.physik.tu-darmstadt.de>

        * include/bits/istream.tcc: change type of __extracted to __size_type 


As pointed by Benjamin, the change

2001-02-11  Gabriel Dos Reis  <gdr@codesourcery.com>

	* include/bits/char_traits.h char_traits<char>::int_type: Change
	to `int' to match 21.1.3.1/2.

	* testsuite/21_strings/char_traits-int_type.C: New test.

seems to have non trivial repercussions.

Here the problem is that the following code (from
  template<typename _CharT, typename _Traits>
    basic_istream<_CharT, _Traits>&
    operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s):
in istream.tcc):

	    int_type __num = static_cast<int_type>(__in.width());
	    if (__num <= 0)
	      __num = basic_string<_CharT, _Traits>::npos;

assume that __num is unsigned.

The following patch corrects the problem mentionned above, but it 
looks like the implications of Gaby's patch need to be looked at 
closely.

	Theo.

Index: istream.tcc
===================================================================
RCS file: /cvs/gcc/egcs/libstdc++-v3/include/bits/istream.tcc,v
retrieving revision 1.9
diff -c -3 -p -r1.9 istream.tcc
*** istream.tcc 2001/03/04 21:34:00     1.9
--- istream.tcc 2001/03/05 17:38:23
*************** namespace std {
*** 1016,1029 ****
        typedef typename _Traits::int_type              int_type;
        typedef _CharT                                  char_type;
        typedef ctype<_CharT>                           __ctype_type;
!       int_type __extracted = 0;
  
        typename __istream_type::sentry __cerb(__in, false);
        if (__cerb)
        {
          try {
            // Figure out how many characters to extract.
!           int_type __num = static_cast<int_type>(__in.width());
            if (__num <= 0)
              __num = basic_string<_CharT, _Traits>::npos;
  
--- 1016,1030 ----
        typedef typename _Traits::int_type              int_type;
        typedef _CharT                                  char_type;
        typedef ctype<_CharT>                           __ctype_type;
!       typedef size_t                                  __size_type;
!       __size_type __extracted = 0;
  
        typename __istream_type::sentry __cerb(__in, false);
        if (__cerb)
        {
          try {
            // Figure out how many characters to extract.
!           __size_type __num = _in.width();
            if (__num <= 0)
              __num = basic_string<_CharT, _Traits>::npos;


 --------------------------------------------------------------------
 Theodore Papadopoulo
 Email: Theodore.Papadopoulo@sophia.inria.fr Tel: (33) 04 92 38 76 01
 --------------------------------------------------------------------

PGP signature