PR 3983, basic_istringstream<unsigned char> fails

[Craig Rodrigues]

Hi,

I was looking at PR 3983:
http://gcc.gnu.org/ml/gcc-prs/2001-08/msg00154.html

I modified the testcase, and it fails under gcc 3.1:

================================================================
#include <sstream>
#include <iostream>
#include <exception>

using namespace std;

int
main ()
{
  int v;
  unsigned char s[2];
  s[0] = '1';
  s[1] = 0;

  try
  {
    basic_istringstream < unsigned char, 
                          std::char_traits < unsigned char >,
                          std::allocator < unsigned char > >strm (s);
    cout << "---" << endl;
    strm >> v;
    cerr << "result: " << v << endl;
  }
  catch (exception & e)
  {
    cout << e.what () << endl;
  }
  return 0;
}

================================================================

% ./a.out
St8bad_cast


If I trace the stack:
#0  0x40132811 in __kill () from /lib/libc.so.6
#1  0x4013258d in raise (sig=6) at ../sysdeps/posix/raise.c:27
#2  0x40133bf8 in abort () at ../sysdeps/generic/abort.c:88
#3  0x400626e4 in __cxxabiv1::__terminate(void (*)()) (
    handler=0x40133a5c <abort>) at eh_terminate.cc:47
#4  0x40062722 in std::terminate() () at eh_terminate.cc:57
#5  0x400628b5 in __cxa_throw () at eh_throw.cc:77
#6  0x40059003 in std::__throw_bad_cast() () at functexcept.cc:49
#7  0x0804a517 in std::basic_ios<unsigned char, std::char_traits<unsigned char> >::_M_check_facet(std::locale::facet const*) const (
    this=0xbffff688, __f=0x0) at basic_ios.h:195
#8  0x0804a967 in std::basic_ios<unsigned char, std::char_traits<unsigned char> >::widen(char) const (this=0xbffff688, __c=32 ' ')
    at basic_ios.tcc:120
#9  0x0804a314 in std::basic_ios<unsigned char, std::char_traits<unsigned char> >::init(std::basic_streambuf<unsigned char, std::char_traits<unsigned char> >*) (this=0xbffff688, __sb=0x0) at basic_ios.tcc:157
#10 0x0804a0f2 in basic_istream (this=0xbffff630,
    __vtt_parm=0x804ea50, __sb=0x0) at istream:78
#11 0x08049bc1 in basic_istringstream (this=0xbffff630,
    __str=@0xbffff620, __mode=8) at sstream:233
#12 0x08049733 in main () at a.cpp:19



The problem seems to be caused by line 157 of basic_ios.tcc:

 _M_fill = this->widen(' ');  


What is this line doing?  Why are we calling widen(char) if
we are using a CharT of unsigned char?


-- 
Craig Rodrigues        
http://www.gis.net/~craigr    
rodrigc@attbi.com