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      1 // Components for manipulating sequences of characters -*- C++ -*-
      2 
      3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
      4 // 2006, 2007, 2008, 2009, 2010, 2011
      5 // Free Software Foundation, Inc.
      6 //
      7 // This file is part of the GNU ISO C++ Library.  This library is free
      8 // software; you can redistribute it and/or modify it under the
      9 // terms of the GNU General Public License as published by the
     10 // Free Software Foundation; either version 3, or (at your option)
     11 // any later version.
     12 
     13 // This library is distributed in the hope that it will be useful,
     14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
     15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     16 // GNU General Public License for more details.
     17 
     18 // Under Section 7 of GPL version 3, you are granted additional
     19 // permissions described in the GCC Runtime Library Exception, version
     20 // 3.1, as published by the Free Software Foundation.
     21 
     22 // You should have received a copy of the GNU General Public License and
     23 // a copy of the GCC Runtime Library Exception along with this program;
     24 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     25 // <http://www.gnu.org/licenses/>.
     26 
     27 /** @file bits/basic_string.tcc
     28  *  This is an internal header file, included by other library headers.
     29  *  Do not attempt to use it directly. @headername{string}
     30  */
     31 
     32 //
     33 // ISO C++ 14882: 21  Strings library
     34 //
     35 
     36 // Written by Jason Merrill based upon the specification by Takanori Adachi
     37 // in ANSI X3J16/94-0013R2.  Rewritten by Nathan Myers to ISO-14882.
     38 
     39 #ifndef _BASIC_STRING_TCC
     40 #define _BASIC_STRING_TCC 1
     41 
     42 #pragma GCC system_header
     43 
     44 #include <bits/cxxabi_forced.h>
     45 
     46 namespace std _GLIBCXX_VISIBILITY(default)
     47 {
     48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     49 
     50   template<typename _CharT, typename _Traits, typename _Alloc>
     51     const typename basic_string<_CharT, _Traits, _Alloc>::size_type
     52     basic_string<_CharT, _Traits, _Alloc>::
     53     _Rep::_S_max_size = (((npos - sizeof(_Rep_base))/sizeof(_CharT)) - 1) / 4;
     54 
     55   template<typename _CharT, typename _Traits, typename _Alloc>
     56     const _CharT
     57     basic_string<_CharT, _Traits, _Alloc>::
     58     _Rep::_S_terminal = _CharT();
     59 
     60   template<typename _CharT, typename _Traits, typename _Alloc>
     61     const typename basic_string<_CharT, _Traits, _Alloc>::size_type
     62     basic_string<_CharT, _Traits, _Alloc>::npos;
     63 
     64   // Linker sets _S_empty_rep_storage to all 0s (one reference, empty string)
     65   // at static init time (before static ctors are run).
     66   template<typename _CharT, typename _Traits, typename _Alloc>
     67     typename basic_string<_CharT, _Traits, _Alloc>::size_type
     68     basic_string<_CharT, _Traits, _Alloc>::_Rep::_S_empty_rep_storage[
     69     (sizeof(_Rep_base) + sizeof(_CharT) + sizeof(size_type) - 1) /
     70       sizeof(size_type)];
     71 
     72   // NB: This is the special case for Input Iterators, used in
     73   // istreambuf_iterators, etc.
     74   // Input Iterators have a cost structure very different from
     75   // pointers, calling for a different coding style.
     76   template<typename _CharT, typename _Traits, typename _Alloc>
     77     template<typename _InIterator>
     78       _CharT*
     79       basic_string<_CharT, _Traits, _Alloc>::
     80       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
     81 		   input_iterator_tag)
     82       {
     83 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
     84 	if (__beg == __end && __a == _Alloc())
     85 	  return _S_empty_rep()._M_refdata();
     86 #endif
     87 	// Avoid reallocation for common case.
     88 	_CharT __buf[128];
     89 	size_type __len = 0;
     90 	while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
     91 	  {
     92 	    __buf[__len++] = *__beg;
     93 	    ++__beg;
     94 	  }
     95 	_Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
     96 	_M_copy(__r->_M_refdata(), __buf, __len);
     97 	__try
     98 	  {
     99 	    while (__beg != __end)
    100 	      {
    101 		if (__len == __r->_M_capacity)
    102 		  {
    103 		    // Allocate more space.
    104 		    _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
    105 		    _M_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
    106 		    __r->_M_destroy(__a);
    107 		    __r = __another;
    108 		  }
    109 		__r->_M_refdata()[__len++] = *__beg;
    110 		++__beg;
    111 	      }
    112 	  }
    113 	__catch(...)
    114 	  {
    115 	    __r->_M_destroy(__a);
    116 	    __throw_exception_again;
    117 	  }
    118 	__r->_M_set_length_and_sharable(__len);
    119 	return __r->_M_refdata();
    120       }
    121 
    122   template<typename _CharT, typename _Traits, typename _Alloc>
    123     template <typename _InIterator>
    124       _CharT*
    125       basic_string<_CharT, _Traits, _Alloc>::
    126       _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
    127 		   forward_iterator_tag)
    128       {
    129 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
    130 	if (__beg == __end && __a == _Alloc())
    131 	  return _S_empty_rep()._M_refdata();
    132 #endif
    133 	// NB: Not required, but considered best practice.
    134 	if (__gnu_cxx::__is_null_pointer(__beg) && __beg != __end)
    135 	  __throw_logic_error(__N("basic_string::_S_construct null not valid"));
    136 
    137 	const size_type __dnew = static_cast<size_type>(std::distance(__beg,
    138 								      __end));
    139 	// Check for out_of_range and length_error exceptions.
    140 	_Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
    141 	__try
    142 	  { _S_copy_chars(__r->_M_refdata(), __beg, __end); }
    143 	__catch(...)
    144 	  {
    145 	    __r->_M_destroy(__a);
    146 	    __throw_exception_again;
    147 	  }
    148 	__r->_M_set_length_and_sharable(__dnew);
    149 	return __r->_M_refdata();
    150       }
    151 
    152   template<typename _CharT, typename _Traits, typename _Alloc>
    153     _CharT*
    154     basic_string<_CharT, _Traits, _Alloc>::
    155     _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
    156     {
    157 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
    158       if (__n == 0 && __a == _Alloc())
    159 	return _S_empty_rep()._M_refdata();
    160 #endif
    161       // Check for out_of_range and length_error exceptions.
    162       _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
    163       if (__n)
    164 	_M_assign(__r->_M_refdata(), __n, __c);
    165 
    166       __r->_M_set_length_and_sharable(__n);
    167       return __r->_M_refdata();
    168     }
    169 
    170   template<typename _CharT, typename _Traits, typename _Alloc>
    171     basic_string<_CharT, _Traits, _Alloc>::
    172     basic_string(const basic_string& __str)
    173     : _M_dataplus(__str._M_rep()->_M_grab(_Alloc(__str.get_allocator()),
    174 					  __str.get_allocator()),
    175 		  __str.get_allocator())
    176     { }
    177 
    178   template<typename _CharT, typename _Traits, typename _Alloc>
    179     basic_string<_CharT, _Traits, _Alloc>::
    180     basic_string(const _Alloc& __a)
    181     : _M_dataplus(_S_construct(size_type(), _CharT(), __a), __a)
    182     { }
    183 
    184   template<typename _CharT, typename _Traits, typename _Alloc>
    185     basic_string<_CharT, _Traits, _Alloc>::
    186     basic_string(const basic_string& __str, size_type __pos, size_type __n)
    187     : _M_dataplus(_S_construct(__str._M_data()
    188 			       + __str._M_check(__pos,
    189 						"basic_string::basic_string"),
    190 			       __str._M_data() + __str._M_limit(__pos, __n)
    191 			       + __pos, _Alloc()), _Alloc())
    192     { }
    193 
    194   template<typename _CharT, typename _Traits, typename _Alloc>
    195     basic_string<_CharT, _Traits, _Alloc>::
    196     basic_string(const basic_string& __str, size_type __pos,
    197 		 size_type __n, const _Alloc& __a)
    198     : _M_dataplus(_S_construct(__str._M_data()
    199 			       + __str._M_check(__pos,
    200 						"basic_string::basic_string"),
    201 			       __str._M_data() + __str._M_limit(__pos, __n)
    202 			       + __pos, __a), __a)
    203     { }
    204 
    205   // TBD: DPG annotate
    206   template<typename _CharT, typename _Traits, typename _Alloc>
    207     basic_string<_CharT, _Traits, _Alloc>::
    208     basic_string(const _CharT* __s, size_type __n, const _Alloc& __a)
    209     : _M_dataplus(_S_construct(__s, __s + __n, __a), __a)
    210     { }
    211 
    212   // TBD: DPG annotate
    213   template<typename _CharT, typename _Traits, typename _Alloc>
    214     basic_string<_CharT, _Traits, _Alloc>::
    215     basic_string(const _CharT* __s, const _Alloc& __a)
    216     : _M_dataplus(_S_construct(__s, __s ? __s + traits_type::length(__s) :
    217 			       __s + npos, __a), __a)
    218     { }
    219 
    220   template<typename _CharT, typename _Traits, typename _Alloc>
    221     basic_string<_CharT, _Traits, _Alloc>::
    222     basic_string(size_type __n, _CharT __c, const _Alloc& __a)
    223     : _M_dataplus(_S_construct(__n, __c, __a), __a)
    224     { }
    225 
    226   // TBD: DPG annotate
    227   template<typename _CharT, typename _Traits, typename _Alloc>
    228     template<typename _InputIterator>
    229     basic_string<_CharT, _Traits, _Alloc>::
    230     basic_string(_InputIterator __beg, _InputIterator __end, const _Alloc& __a)
    231     : _M_dataplus(_S_construct(__beg, __end, __a), __a)
    232     { }
    233 
    234 #ifdef __GXX_EXPERIMENTAL_CXX0X__
    235   template<typename _CharT, typename _Traits, typename _Alloc>
    236     basic_string<_CharT, _Traits, _Alloc>::
    237     basic_string(initializer_list<_CharT> __l, const _Alloc& __a)
    238     : _M_dataplus(_S_construct(__l.begin(), __l.end(), __a), __a)
    239     { }
    240 #endif
    241 
    242   template<typename _CharT, typename _Traits, typename _Alloc>
    243     basic_string<_CharT, _Traits, _Alloc>&
    244     basic_string<_CharT, _Traits, _Alloc>::
    245     assign(const basic_string& __str)
    246     {
    247       if (_M_rep() != __str._M_rep())
    248 	{
    249 	  // XXX MT
    250 	  const allocator_type __a = this->get_allocator();
    251 	  _CharT* __tmp = __str._M_rep()->_M_grab(__a, __str.get_allocator());
    252 	  _M_rep()->_M_dispose(__a);
    253 	  _M_data(__tmp);
    254 	}
    255       return *this;
    256     }
    257 
    258   template<typename _CharT, typename _Traits, typename _Alloc>
    259     basic_string<_CharT, _Traits, _Alloc>&
    260     basic_string<_CharT, _Traits, _Alloc>::
    261     assign(const _CharT* __s, size_type __n)
    262     {
    263       __glibcxx_requires_string_len(__s, __n);
    264       _M_check_length(this->size(), __n, "basic_string::assign");
    265       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
    266 	return _M_replace_safe(size_type(0), this->size(), __s, __n);
    267       else
    268 	{
    269 	  // Work in-place.
    270 	  const size_type __pos = __s - _M_data();
    271 	  if (__pos >= __n)
    272 	    _M_copy(_M_data(), __s, __n);
    273 	  else if (__pos)
    274 	    _M_move(_M_data(), __s, __n);
    275 	  _M_rep()->_M_set_length_and_sharable(__n);
    276 	  return *this;
    277 	}
    278      }
    279 
    280   template<typename _CharT, typename _Traits, typename _Alloc>
    281     basic_string<_CharT, _Traits, _Alloc>&
    282     basic_string<_CharT, _Traits, _Alloc>::
    283     append(size_type __n, _CharT __c)
    284     {
    285       if (__n)
    286 	{
    287 	  _M_check_length(size_type(0), __n, "basic_string::append");	  
    288 	  const size_type __len = __n + this->size();
    289 	  if (__len > this->capacity() || _M_rep()->_M_is_shared())
    290 	    this->reserve(__len);
    291 	  _M_assign(_M_data() + this->size(), __n, __c);
    292 	  _M_rep()->_M_set_length_and_sharable(__len);
    293 	}
    294       return *this;
    295     }
    296 
    297   template<typename _CharT, typename _Traits, typename _Alloc>
    298     basic_string<_CharT, _Traits, _Alloc>&
    299     basic_string<_CharT, _Traits, _Alloc>::
    300     append(const _CharT* __s, size_type __n)
    301     {
    302       __glibcxx_requires_string_len(__s, __n);
    303       if (__n)
    304 	{
    305 	  _M_check_length(size_type(0), __n, "basic_string::append");
    306 	  const size_type __len = __n + this->size();
    307 	  if (__len > this->capacity() || _M_rep()->_M_is_shared())
    308 	    {
    309 	      if (_M_disjunct(__s))
    310 		this->reserve(__len);
    311 	      else
    312 		{
    313 		  const size_type __off = __s - _M_data();
    314 		  this->reserve(__len);
    315 		  __s = _M_data() + __off;
    316 		}
    317 	    }
    318 	  _M_copy(_M_data() + this->size(), __s, __n);
    319 	  _M_rep()->_M_set_length_and_sharable(__len);
    320 	}
    321       return *this;
    322     }
    323 
    324   template<typename _CharT, typename _Traits, typename _Alloc>
    325     basic_string<_CharT, _Traits, _Alloc>&
    326     basic_string<_CharT, _Traits, _Alloc>::
    327     append(const basic_string& __str)
    328     {
    329       const size_type __size = __str.size();
    330       if (__size)
    331 	{
    332 	  const size_type __len = __size + this->size();
    333 	  if (__len > this->capacity() || _M_rep()->_M_is_shared())
    334 	    this->reserve(__len);
    335 	  _M_copy(_M_data() + this->size(), __str._M_data(), __size);
    336 	  _M_rep()->_M_set_length_and_sharable(__len);
    337 	}
    338       return *this;
    339     }    
    340 
    341   template<typename _CharT, typename _Traits, typename _Alloc>
    342     basic_string<_CharT, _Traits, _Alloc>&
    343     basic_string<_CharT, _Traits, _Alloc>::
    344     append(const basic_string& __str, size_type __pos, size_type __n)
    345     {
    346       __str._M_check(__pos, "basic_string::append");
    347       __n = __str._M_limit(__pos, __n);
    348       if (__n)
    349 	{
    350 	  const size_type __len = __n + this->size();
    351 	  if (__len > this->capacity() || _M_rep()->_M_is_shared())
    352 	    this->reserve(__len);
    353 	  _M_copy(_M_data() + this->size(), __str._M_data() + __pos, __n);
    354 	  _M_rep()->_M_set_length_and_sharable(__len);	  
    355 	}
    356       return *this;
    357     }
    358 
    359    template<typename _CharT, typename _Traits, typename _Alloc>
    360      basic_string<_CharT, _Traits, _Alloc>&
    361      basic_string<_CharT, _Traits, _Alloc>::
    362      insert(size_type __pos, const _CharT* __s, size_type __n)
    363      {
    364        __glibcxx_requires_string_len(__s, __n);
    365        _M_check(__pos, "basic_string::insert");
    366        _M_check_length(size_type(0), __n, "basic_string::insert");
    367        if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
    368          return _M_replace_safe(__pos, size_type(0), __s, __n);
    369        else
    370          {
    371            // Work in-place.
    372            const size_type __off = __s - _M_data();
    373            _M_mutate(__pos, 0, __n);
    374            __s = _M_data() + __off;
    375            _CharT* __p = _M_data() + __pos;
    376            if (__s  + __n <= __p)
    377              _M_copy(__p, __s, __n);
    378            else if (__s >= __p)
    379              _M_copy(__p, __s + __n, __n);
    380            else
    381              {
    382 	       const size_type __nleft = __p - __s;
    383                _M_copy(__p, __s, __nleft);
    384                _M_copy(__p + __nleft, __p + __n, __n - __nleft);
    385              }
    386            return *this;
    387          }
    388      }
    389 
    390    template<typename _CharT, typename _Traits, typename _Alloc>
    391      typename basic_string<_CharT, _Traits, _Alloc>::iterator
    392      basic_string<_CharT, _Traits, _Alloc>::
    393      erase(iterator __first, iterator __last)
    394      {
    395        _GLIBCXX_DEBUG_PEDASSERT(__first >= _M_ibegin() && __first <= __last
    396 				&& __last <= _M_iend());
    397 
    398        // NB: This isn't just an optimization (bail out early when
    399        // there is nothing to do, really), it's also a correctness
    400        // issue vs MT, see libstdc++/40518.
    401        const size_type __size = __last - __first;
    402        if (__size)
    403 	 {
    404 	   const size_type __pos = __first - _M_ibegin();
    405 	   _M_mutate(__pos, __size, size_type(0));
    406 	   _M_rep()->_M_set_leaked();
    407 	   return iterator(_M_data() + __pos);
    408 	 }
    409        else
    410 	 return __first;
    411      }
    412 
    413    template<typename _CharT, typename _Traits, typename _Alloc>
    414      basic_string<_CharT, _Traits, _Alloc>&
    415      basic_string<_CharT, _Traits, _Alloc>::
    416      replace(size_type __pos, size_type __n1, const _CharT* __s,
    417 	     size_type __n2)
    418      {
    419        __glibcxx_requires_string_len(__s, __n2);
    420        _M_check(__pos, "basic_string::replace");
    421        __n1 = _M_limit(__pos, __n1);
    422        _M_check_length(__n1, __n2, "basic_string::replace");
    423        bool __left;
    424        if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
    425          return _M_replace_safe(__pos, __n1, __s, __n2);
    426        else if ((__left = __s + __n2 <= _M_data() + __pos)
    427 		|| _M_data() + __pos + __n1 <= __s)
    428 	 {
    429 	   // Work in-place: non-overlapping case.
    430 	   size_type __off = __s - _M_data();
    431 	   __left ? __off : (__off += __n2 - __n1);
    432 	   _M_mutate(__pos, __n1, __n2);
    433 	   _M_copy(_M_data() + __pos, _M_data() + __off, __n2);
    434 	   return *this;
    435 	 }
    436        else
    437 	 {
    438 	   // Todo: overlapping case.
    439 	   const basic_string __tmp(__s, __n2);
    440 	   return _M_replace_safe(__pos, __n1, __tmp._M_data(), __n2);
    441 	 }
    442      }
    443 
    444   template<typename _CharT, typename _Traits, typename _Alloc>
    445     void
    446     basic_string<_CharT, _Traits, _Alloc>::_Rep::
    447     _M_destroy(const _Alloc& __a) throw ()
    448     {
    449       const size_type __size = sizeof(_Rep_base) +
    450 	                       (this->_M_capacity + 1) * sizeof(_CharT);
    451       _Raw_bytes_alloc(__a).deallocate(reinterpret_cast<char*>(this), __size);
    452     }
    453 
    454   template<typename _CharT, typename _Traits, typename _Alloc>
    455     void
    456     basic_string<_CharT, _Traits, _Alloc>::
    457     _M_leak_hard()
    458     {
    459 #ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
    460       if (_M_rep() == &_S_empty_rep())
    461 	return;
    462 #endif
    463       if (_M_rep()->_M_is_shared())
    464 	_M_mutate(0, 0, 0);
    465       _M_rep()->_M_set_leaked();
    466     }
    467 
    468   template<typename _CharT, typename _Traits, typename _Alloc>
    469     void
    470     basic_string<_CharT, _Traits, _Alloc>::
    471     _M_mutate(size_type __pos, size_type __len1, size_type __len2)
    472     {
    473       const size_type __old_size = this->size();
    474       const size_type __new_size = __old_size + __len2 - __len1;
    475       const size_type __how_much = __old_size - __pos - __len1;
    476 
    477       if (__new_size > this->capacity() || _M_rep()->_M_is_shared())
    478 	{
    479 	  // Must reallocate.
    480 	  const allocator_type __a = get_allocator();
    481 	  _Rep* __r = _Rep::_S_create(__new_size, this->capacity(), __a);
    482 
    483 	  if (__pos)
    484 	    _M_copy(__r->_M_refdata(), _M_data(), __pos);
    485 	  if (__how_much)
    486 	    _M_copy(__r->_M_refdata() + __pos + __len2,
    487 		    _M_data() + __pos + __len1, __how_much);
    488 
    489 	  _M_rep()->_M_dispose(__a);
    490 	  _M_data(__r->_M_refdata());
    491 	}
    492       else if (__how_much && __len1 != __len2)
    493 	{
    494 	  // Work in-place.
    495 	  _M_move(_M_data() + __pos + __len2,
    496 		  _M_data() + __pos + __len1, __how_much);
    497 	}
    498       _M_rep()->_M_set_length_and_sharable(__new_size);
    499     }
    500 
    501   template<typename _CharT, typename _Traits, typename _Alloc>
    502     void
    503     basic_string<_CharT, _Traits, _Alloc>::
    504     reserve(size_type __res)
    505     {
    506       if (__res != this->capacity() || _M_rep()->_M_is_shared())
    507         {
    508 	  // Make sure we don't shrink below the current size
    509 	  if (__res < this->size())
    510 	    __res = this->size();
    511 	  const allocator_type __a = get_allocator();
    512 	  _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
    513 	  _M_rep()->_M_dispose(__a);
    514 	  _M_data(__tmp);
    515         }
    516     }
    517 
    518   template<typename _CharT, typename _Traits, typename _Alloc>
    519     void
    520     basic_string<_CharT, _Traits, _Alloc>::
    521     swap(basic_string& __s)
    522     {
    523       if (_M_rep()->_M_is_leaked())
    524 	_M_rep()->_M_set_sharable();
    525       if (__s._M_rep()->_M_is_leaked())
    526 	__s._M_rep()->_M_set_sharable();
    527       if (this->get_allocator() == __s.get_allocator())
    528 	{
    529 	  _CharT* __tmp = _M_data();
    530 	  _M_data(__s._M_data());
    531 	  __s._M_data(__tmp);
    532 	}
    533       // The code below can usually be optimized away.
    534       else
    535 	{
    536 	  const basic_string __tmp1(_M_ibegin(), _M_iend(),
    537 				    __s.get_allocator());
    538 	  const basic_string __tmp2(__s._M_ibegin(), __s._M_iend(),
    539 				    this->get_allocator());
    540 	  *this = __tmp2;
    541 	  __s = __tmp1;
    542 	}
    543     }
    544 
    545   template<typename _CharT, typename _Traits, typename _Alloc>
    546     typename basic_string<_CharT, _Traits, _Alloc>::_Rep*
    547     basic_string<_CharT, _Traits, _Alloc>::_Rep::
    548     _S_create(size_type __capacity, size_type __old_capacity,
    549 	      const _Alloc& __alloc)
    550     {
    551       // _GLIBCXX_RESOLVE_LIB_DEFECTS
    552       // 83.  String::npos vs. string::max_size()
    553       if (__capacity > _S_max_size)
    554 	__throw_length_error(__N("basic_string::_S_create"));
    555 
    556       // The standard places no restriction on allocating more memory
    557       // than is strictly needed within this layer at the moment or as
    558       // requested by an explicit application call to reserve().
    559 
    560       // Many malloc implementations perform quite poorly when an
    561       // application attempts to allocate memory in a stepwise fashion
    562       // growing each allocation size by only 1 char.  Additionally,
    563       // it makes little sense to allocate less linear memory than the
    564       // natural blocking size of the malloc implementation.
    565       // Unfortunately, we would need a somewhat low-level calculation
    566       // with tuned parameters to get this perfect for any particular
    567       // malloc implementation.  Fortunately, generalizations about
    568       // common features seen among implementations seems to suffice.
    569 
    570       // __pagesize need not match the actual VM page size for good
    571       // results in practice, thus we pick a common value on the low
    572       // side.  __malloc_header_size is an estimate of the amount of
    573       // overhead per memory allocation (in practice seen N * sizeof
    574       // (void*) where N is 0, 2 or 4).  According to folklore,
    575       // picking this value on the high side is better than
    576       // low-balling it (especially when this algorithm is used with
    577       // malloc implementations that allocate memory blocks rounded up
    578       // to a size which is a power of 2).
    579       const size_type __pagesize = 4096;
    580       const size_type __malloc_header_size = 4 * sizeof(void*);
    581 
    582       // The below implements an exponential growth policy, necessary to
    583       // meet amortized linear time requirements of the library: see
    584       // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
    585       // It's active for allocations requiring an amount of memory above
    586       // system pagesize. This is consistent with the requirements of the
    587       // standard: http://gcc.gnu.org/ml/libstdc++/2001-07/msg00130.html
    588       if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
    589 	__capacity = 2 * __old_capacity;
    590 
    591       // NB: Need an array of char_type[__capacity], plus a terminating
    592       // null char_type() element, plus enough for the _Rep data structure.
    593       // Whew. Seemingly so needy, yet so elemental.
    594       size_type __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
    595 
    596       const size_type __adj_size = __size + __malloc_header_size;
    597       if (__adj_size > __pagesize && __capacity > __old_capacity)
    598 	{
    599 	  const size_type __extra = __pagesize - __adj_size % __pagesize;
    600 	  __capacity += __extra / sizeof(_CharT);
    601 	  // Never allocate a string bigger than _S_max_size.
    602 	  if (__capacity > _S_max_size)
    603 	    __capacity = _S_max_size;
    604 	  __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
    605 	}
    606 
    607       // NB: Might throw, but no worries about a leak, mate: _Rep()
    608       // does not throw.
    609       void* __place = _Raw_bytes_alloc(__alloc).allocate(__size);
    610       _Rep *__p = new (__place) _Rep;
    611       __p->_M_capacity = __capacity;
    612       // ABI compatibility - 3.4.x set in _S_create both
    613       // _M_refcount and _M_length.  All callers of _S_create
    614       // in basic_string.tcc then set just _M_length.
    615       // In 4.0.x and later both _M_refcount and _M_length
    616       // are initialized in the callers, unfortunately we can
    617       // have 3.4.x compiled code with _S_create callers inlined
    618       // calling 4.0.x+ _S_create.
    619       __p->_M_set_sharable();
    620       return __p;
    621     }
    622 
    623   template<typename _CharT, typename _Traits, typename _Alloc>
    624     _CharT*
    625     basic_string<_CharT, _Traits, _Alloc>::_Rep::
    626     _M_clone(const _Alloc& __alloc, size_type __res)
    627     {
    628       // Requested capacity of the clone.
    629       const size_type __requested_cap = this->_M_length + __res;
    630       _Rep* __r = _Rep::_S_create(__requested_cap, this->_M_capacity,
    631 				  __alloc);
    632       if (this->_M_length)
    633 	_M_copy(__r->_M_refdata(), _M_refdata(), this->_M_length);
    634 
    635       __r->_M_set_length_and_sharable(this->_M_length);
    636       return __r->_M_refdata();
    637     }
    638 
    639   template<typename _CharT, typename _Traits, typename _Alloc>
    640     void
    641     basic_string<_CharT, _Traits, _Alloc>::
    642     resize(size_type __n, _CharT __c)
    643     {
    644       const size_type __size = this->size();
    645       _M_check_length(__size, __n, "basic_string::resize");
    646       if (__size < __n)
    647 	this->append(__n - __size, __c);
    648       else if (__n < __size)
    649 	this->erase(__n);
    650       // else nothing (in particular, avoid calling _M_mutate() unnecessarily.)
    651     }
    652 
    653   template<typename _CharT, typename _Traits, typename _Alloc>
    654     template<typename _InputIterator>
    655       basic_string<_CharT, _Traits, _Alloc>&
    656       basic_string<_CharT, _Traits, _Alloc>::
    657       _M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator __k1,
    658 			  _InputIterator __k2, __false_type)
    659       {
    660 	const basic_string __s(__k1, __k2);
    661 	const size_type __n1 = __i2 - __i1;
    662 	_M_check_length(__n1, __s.size(), "basic_string::_M_replace_dispatch");
    663 	return _M_replace_safe(__i1 - _M_ibegin(), __n1, __s._M_data(),
    664 			       __s.size());
    665       }
    666 
    667   template<typename _CharT, typename _Traits, typename _Alloc>
    668     basic_string<_CharT, _Traits, _Alloc>&
    669     basic_string<_CharT, _Traits, _Alloc>::
    670     _M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
    671 		   _CharT __c)
    672     {
    673       _M_check_length(__n1, __n2, "basic_string::_M_replace_aux");
    674       _M_mutate(__pos1, __n1, __n2);
    675       if (__n2)
    676 	_M_assign(_M_data() + __pos1, __n2, __c);
    677       return *this;
    678     }
    679 
    680   template<typename _CharT, typename _Traits, typename _Alloc>
    681     basic_string<_CharT, _Traits, _Alloc>&
    682     basic_string<_CharT, _Traits, _Alloc>::
    683     _M_replace_safe(size_type __pos1, size_type __n1, const _CharT* __s,
    684 		    size_type __n2)
    685     {
    686       _M_mutate(__pos1, __n1, __n2);
    687       if (__n2)
    688 	_M_copy(_M_data() + __pos1, __s, __n2);
    689       return *this;
    690     }
    691    
    692   template<typename _CharT, typename _Traits, typename _Alloc>
    693     basic_string<_CharT, _Traits, _Alloc>
    694     operator+(const _CharT* __lhs,
    695 	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
    696     {
    697       __glibcxx_requires_string(__lhs);
    698       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
    699       typedef typename __string_type::size_type	  __size_type;
    700       const __size_type __len = _Traits::length(__lhs);
    701       __string_type __str;
    702       __str.reserve(__len + __rhs.size());
    703       __str.append(__lhs, __len);
    704       __str.append(__rhs);
    705       return __str;
    706     }
    707 
    708   template<typename _CharT, typename _Traits, typename _Alloc>
    709     basic_string<_CharT, _Traits, _Alloc>
    710     operator+(_CharT __lhs, const basic_string<_CharT, _Traits, _Alloc>& __rhs)
    711     {
    712       typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
    713       typedef typename __string_type::size_type	  __size_type;
    714       __string_type __str;
    715       const __size_type __len = __rhs.size();
    716       __str.reserve(__len + 1);
    717       __str.append(__size_type(1), __lhs);
    718       __str.append(__rhs);
    719       return __str;
    720     }
    721 
    722   template<typename _CharT, typename _Traits, typename _Alloc>
    723     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    724     basic_string<_CharT, _Traits, _Alloc>::
    725     copy(_CharT* __s, size_type __n, size_type __pos) const
    726     {
    727       _M_check(__pos, "basic_string::copy");
    728       __n = _M_limit(__pos, __n);
    729       __glibcxx_requires_string_len(__s, __n);
    730       if (__n)
    731 	_M_copy(__s, _M_data() + __pos, __n);
    732       // 21.3.5.7 par 3: do not append null.  (good.)
    733       return __n;
    734     }
    735 
    736   template<typename _CharT, typename _Traits, typename _Alloc>
    737     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    738     basic_string<_CharT, _Traits, _Alloc>::
    739     find(const _CharT* __s, size_type __pos, size_type __n) const
    740     {
    741       __glibcxx_requires_string_len(__s, __n);
    742       const size_type __size = this->size();
    743       const _CharT* __data = _M_data();
    744 
    745       if (__n == 0)
    746 	return __pos <= __size ? __pos : npos;
    747 
    748       if (__n <= __size)
    749 	{
    750 	  for (; __pos <= __size - __n; ++__pos)
    751 	    if (traits_type::eq(__data[__pos], __s[0])
    752 		&& traits_type::compare(__data + __pos + 1,
    753 					__s + 1, __n - 1) == 0)
    754 	      return __pos;
    755 	}
    756       return npos;
    757     }
    758 
    759   template<typename _CharT, typename _Traits, typename _Alloc>
    760     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    761     basic_string<_CharT, _Traits, _Alloc>::
    762     find(_CharT __c, size_type __pos) const
    763     {
    764       size_type __ret = npos;
    765       const size_type __size = this->size();
    766       if (__pos < __size)
    767 	{
    768 	  const _CharT* __data = _M_data();
    769 	  const size_type __n = __size - __pos;
    770 	  const _CharT* __p = traits_type::find(__data + __pos, __n, __c);
    771 	  if (__p)
    772 	    __ret = __p - __data;
    773 	}
    774       return __ret;
    775     }
    776 
    777   template<typename _CharT, typename _Traits, typename _Alloc>
    778     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    779     basic_string<_CharT, _Traits, _Alloc>::
    780     rfind(const _CharT* __s, size_type __pos, size_type __n) const
    781     {
    782       __glibcxx_requires_string_len(__s, __n);
    783       const size_type __size = this->size();
    784       if (__n <= __size)
    785 	{
    786 	  __pos = std::min(size_type(__size - __n), __pos);
    787 	  const _CharT* __data = _M_data();
    788 	  do
    789 	    {
    790 	      if (traits_type::compare(__data + __pos, __s, __n) == 0)
    791 		return __pos;
    792 	    }
    793 	  while (__pos-- > 0);
    794 	}
    795       return npos;
    796     }
    797 
    798   template<typename _CharT, typename _Traits, typename _Alloc>
    799     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    800     basic_string<_CharT, _Traits, _Alloc>::
    801     rfind(_CharT __c, size_type __pos) const
    802     {
    803       size_type __size = this->size();
    804       if (__size)
    805 	{
    806 	  if (--__size > __pos)
    807 	    __size = __pos;
    808 	  for (++__size; __size-- > 0; )
    809 	    if (traits_type::eq(_M_data()[__size], __c))
    810 	      return __size;
    811 	}
    812       return npos;
    813     }
    814 
    815   template<typename _CharT, typename _Traits, typename _Alloc>
    816     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    817     basic_string<_CharT, _Traits, _Alloc>::
    818     find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
    819     {
    820       __glibcxx_requires_string_len(__s, __n);
    821       for (; __n && __pos < this->size(); ++__pos)
    822 	{
    823 	  const _CharT* __p = traits_type::find(__s, __n, _M_data()[__pos]);
    824 	  if (__p)
    825 	    return __pos;
    826 	}
    827       return npos;
    828     }
    829 
    830   template<typename _CharT, typename _Traits, typename _Alloc>
    831     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    832     basic_string<_CharT, _Traits, _Alloc>::
    833     find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
    834     {
    835       __glibcxx_requires_string_len(__s, __n);
    836       size_type __size = this->size();
    837       if (__size && __n)
    838 	{
    839 	  if (--__size > __pos)
    840 	    __size = __pos;
    841 	  do
    842 	    {
    843 	      if (traits_type::find(__s, __n, _M_data()[__size]))
    844 		return __size;
    845 	    }
    846 	  while (__size-- != 0);
    847 	}
    848       return npos;
    849     }
    850 
    851   template<typename _CharT, typename _Traits, typename _Alloc>
    852     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    853     basic_string<_CharT, _Traits, _Alloc>::
    854     find_first_not_of(const _CharT* __s, size_type __pos, size_type __n) const
    855     {
    856       __glibcxx_requires_string_len(__s, __n);
    857       for (; __pos < this->size(); ++__pos)
    858 	if (!traits_type::find(__s, __n, _M_data()[__pos]))
    859 	  return __pos;
    860       return npos;
    861     }
    862 
    863   template<typename _CharT, typename _Traits, typename _Alloc>
    864     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    865     basic_string<_CharT, _Traits, _Alloc>::
    866     find_first_not_of(_CharT __c, size_type __pos) const
    867     {
    868       for (; __pos < this->size(); ++__pos)
    869 	if (!traits_type::eq(_M_data()[__pos], __c))
    870 	  return __pos;
    871       return npos;
    872     }
    873 
    874   template<typename _CharT, typename _Traits, typename _Alloc>
    875     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    876     basic_string<_CharT, _Traits, _Alloc>::
    877     find_last_not_of(const _CharT* __s, size_type __pos, size_type __n) const
    878     {
    879       __glibcxx_requires_string_len(__s, __n);
    880       size_type __size = this->size();
    881       if (__size)
    882 	{
    883 	  if (--__size > __pos)
    884 	    __size = __pos;
    885 	  do
    886 	    {
    887 	      if (!traits_type::find(__s, __n, _M_data()[__size]))
    888 		return __size;
    889 	    }
    890 	  while (__size--);
    891 	}
    892       return npos;
    893     }
    894 
    895   template<typename _CharT, typename _Traits, typename _Alloc>
    896     typename basic_string<_CharT, _Traits, _Alloc>::size_type
    897     basic_string<_CharT, _Traits, _Alloc>::
    898     find_last_not_of(_CharT __c, size_type __pos) const
    899     {
    900       size_type __size = this->size();
    901       if (__size)
    902 	{
    903 	  if (--__size > __pos)
    904 	    __size = __pos;
    905 	  do
    906 	    {
    907 	      if (!traits_type::eq(_M_data()[__size], __c))
    908 		return __size;
    909 	    }
    910 	  while (__size--);
    911 	}
    912       return npos;
    913     }
    914 
    915   template<typename _CharT, typename _Traits, typename _Alloc>
    916     int
    917     basic_string<_CharT, _Traits, _Alloc>::
    918     compare(size_type __pos, size_type __n, const basic_string& __str) const
    919     {
    920       _M_check(__pos, "basic_string::compare");
    921       __n = _M_limit(__pos, __n);
    922       const size_type __osize = __str.size();
    923       const size_type __len = std::min(__n, __osize);
    924       int __r = traits_type::compare(_M_data() + __pos, __str.data(), __len);
    925       if (!__r)
    926 	__r = _S_compare(__n, __osize);
    927       return __r;
    928     }
    929 
    930   template<typename _CharT, typename _Traits, typename _Alloc>
    931     int
    932     basic_string<_CharT, _Traits, _Alloc>::
    933     compare(size_type __pos1, size_type __n1, const basic_string& __str,
    934 	    size_type __pos2, size_type __n2) const
    935     {
    936       _M_check(__pos1, "basic_string::compare");
    937       __str._M_check(__pos2, "basic_string::compare");
    938       __n1 = _M_limit(__pos1, __n1);
    939       __n2 = __str._M_limit(__pos2, __n2);
    940       const size_type __len = std::min(__n1, __n2);
    941       int __r = traits_type::compare(_M_data() + __pos1,
    942 				     __str.data() + __pos2, __len);
    943       if (!__r)
    944 	__r = _S_compare(__n1, __n2);
    945       return __r;
    946     }
    947 
    948   template<typename _CharT, typename _Traits, typename _Alloc>
    949     int
    950     basic_string<_CharT, _Traits, _Alloc>::
    951     compare(const _CharT* __s) const
    952     {
    953       __glibcxx_requires_string(__s);
    954       const size_type __size = this->size();
    955       const size_type __osize = traits_type::length(__s);
    956       const size_type __len = std::min(__size, __osize);
    957       int __r = traits_type::compare(_M_data(), __s, __len);
    958       if (!__r)
    959 	__r = _S_compare(__size, __osize);
    960       return __r;
    961     }
    962 
    963   template<typename _CharT, typename _Traits, typename _Alloc>
    964     int
    965     basic_string <_CharT, _Traits, _Alloc>::
    966     compare(size_type __pos, size_type __n1, const _CharT* __s) const
    967     {
    968       __glibcxx_requires_string(__s);
    969       _M_check(__pos, "basic_string::compare");
    970       __n1 = _M_limit(__pos, __n1);
    971       const size_type __osize = traits_type::length(__s);
    972       const size_type __len = std::min(__n1, __osize);
    973       int __r = traits_type::compare(_M_data() + __pos, __s, __len);
    974       if (!__r)
    975 	__r = _S_compare(__n1, __osize);
    976       return __r;
    977     }
    978 
    979   template<typename _CharT, typename _Traits, typename _Alloc>
    980     int
    981     basic_string <_CharT, _Traits, _Alloc>::
    982     compare(size_type __pos, size_type __n1, const _CharT* __s,
    983 	    size_type __n2) const
    984     {
    985       __glibcxx_requires_string_len(__s, __n2);
    986       _M_check(__pos, "basic_string::compare");
    987       __n1 = _M_limit(__pos, __n1);
    988       const size_type __len = std::min(__n1, __n2);
    989       int __r = traits_type::compare(_M_data() + __pos, __s, __len);
    990       if (!__r)
    991 	__r = _S_compare(__n1, __n2);
    992       return __r;
    993     }
    994 
    995   // 21.3.7.9 basic_string::getline and operators
    996   template<typename _CharT, typename _Traits, typename _Alloc>
    997     basic_istream<_CharT, _Traits>&
    998     operator>>(basic_istream<_CharT, _Traits>& __in,
    999 	       basic_string<_CharT, _Traits, _Alloc>& __str)
   1000     {
   1001       typedef basic_istream<_CharT, _Traits>		__istream_type;
   1002       typedef basic_string<_CharT, _Traits, _Alloc>	__string_type;
   1003       typedef typename __istream_type::ios_base         __ios_base;
   1004       typedef typename __istream_type::int_type		__int_type;
   1005       typedef typename __string_type::size_type		__size_type;
   1006       typedef ctype<_CharT>				__ctype_type;
   1007       typedef typename __ctype_type::ctype_base         __ctype_base;
   1008 
   1009       __size_type __extracted = 0;
   1010       typename __ios_base::iostate __err = __ios_base::goodbit;
   1011       typename __istream_type::sentry __cerb(__in, false);
   1012       if (__cerb)
   1013 	{
   1014 	  __try
   1015 	    {
   1016 	      // Avoid reallocation for common case.
   1017 	      __str.erase();
   1018 	      _CharT __buf[128];
   1019 	      __size_type __len = 0;	      
   1020 	      const streamsize __w = __in.width();
   1021 	      const __size_type __n = __w > 0 ? static_cast<__size_type>(__w)
   1022 		                              : __str.max_size();
   1023 	      const __ctype_type& __ct = use_facet<__ctype_type>(__in.getloc());
   1024 	      const __int_type __eof = _Traits::eof();
   1025 	      __int_type __c = __in.rdbuf()->sgetc();
   1026 
   1027 	      while (__extracted < __n
   1028 		     && !_Traits::eq_int_type(__c, __eof)
   1029 		     && !__ct.is(__ctype_base::space,
   1030 				 _Traits::to_char_type(__c)))
   1031 		{
   1032 		  if (__len == sizeof(__buf) / sizeof(_CharT))
   1033 		    {
   1034 		      __str.append(__buf, sizeof(__buf) / sizeof(_CharT));
   1035 		      __len = 0;
   1036 		    }
   1037 		  __buf[__len++] = _Traits::to_char_type(__c);
   1038 		  ++__extracted;
   1039 		  __c = __in.rdbuf()->snextc();
   1040 		}
   1041 	      __str.append(__buf, __len);
   1042 
   1043 	      if (_Traits::eq_int_type(__c, __eof))
   1044 		__err |= __ios_base::eofbit;
   1045 	      __in.width(0);
   1046 	    }
   1047 	  __catch(__cxxabiv1::__forced_unwind&)
   1048 	    {
   1049 	      __in._M_setstate(__ios_base::badbit);
   1050 	      __throw_exception_again;
   1051 	    }
   1052 	  __catch(...)
   1053 	    {
   1054 	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
   1055 	      // 91. Description of operator>> and getline() for string<>
   1056 	      // might cause endless loop
   1057 	      __in._M_setstate(__ios_base::badbit);
   1058 	    }
   1059 	}
   1060       // 211.  operator>>(istream&, string&) doesn't set failbit
   1061       if (!__extracted)
   1062 	__err |= __ios_base::failbit;
   1063       if (__err)
   1064 	__in.setstate(__err);
   1065       return __in;
   1066     }
   1067 
   1068   template<typename _CharT, typename _Traits, typename _Alloc>
   1069     basic_istream<_CharT, _Traits>&
   1070     getline(basic_istream<_CharT, _Traits>& __in,
   1071 	    basic_string<_CharT, _Traits, _Alloc>& __str, _CharT __delim)
   1072     {
   1073       typedef basic_istream<_CharT, _Traits>		__istream_type;
   1074       typedef basic_string<_CharT, _Traits, _Alloc>	__string_type;
   1075       typedef typename __istream_type::ios_base         __ios_base;
   1076       typedef typename __istream_type::int_type		__int_type;
   1077       typedef typename __string_type::size_type		__size_type;
   1078 
   1079       __size_type __extracted = 0;
   1080       const __size_type __n = __str.max_size();
   1081       typename __ios_base::iostate __err = __ios_base::goodbit;
   1082       typename __istream_type::sentry __cerb(__in, true);
   1083       if (__cerb)
   1084 	{
   1085 	  __try
   1086 	    {
   1087 	      __str.erase();
   1088 	      const __int_type __idelim = _Traits::to_int_type(__delim);
   1089 	      const __int_type __eof = _Traits::eof();
   1090 	      __int_type __c = __in.rdbuf()->sgetc();
   1091 
   1092 	      while (__extracted < __n
   1093 		     && !_Traits::eq_int_type(__c, __eof)
   1094 		     && !_Traits::eq_int_type(__c, __idelim))
   1095 		{
   1096 		  __str += _Traits::to_char_type(__c);
   1097 		  ++__extracted;
   1098 		  __c = __in.rdbuf()->snextc();
   1099 		}
   1100 
   1101 	      if (_Traits::eq_int_type(__c, __eof))
   1102 		__err |= __ios_base::eofbit;
   1103 	      else if (_Traits::eq_int_type(__c, __idelim))
   1104 		{
   1105 		  ++__extracted;		  
   1106 		  __in.rdbuf()->sbumpc();
   1107 		}
   1108 	      else
   1109 		__err |= __ios_base::failbit;
   1110 	    }
   1111 	  __catch(__cxxabiv1::__forced_unwind&)
   1112 	    {
   1113 	      __in._M_setstate(__ios_base::badbit);
   1114 	      __throw_exception_again;
   1115 	    }
   1116 	  __catch(...)
   1117 	    {
   1118 	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
   1119 	      // 91. Description of operator>> and getline() for string<>
   1120 	      // might cause endless loop
   1121 	      __in._M_setstate(__ios_base::badbit);
   1122 	    }
   1123 	}
   1124       if (!__extracted)
   1125 	__err |= __ios_base::failbit;
   1126       if (__err)
   1127 	__in.setstate(__err);
   1128       return __in;
   1129     }
   1130 
   1131   // Inhibit implicit instantiations for required instantiations,
   1132   // which are defined via explicit instantiations elsewhere.
   1133 #if _GLIBCXX_EXTERN_TEMPLATE > 0
   1134   extern template class basic_string<char>;
   1135   extern template
   1136     basic_istream<char>&
   1137     operator>>(basic_istream<char>&, string&);
   1138   extern template
   1139     basic_ostream<char>&
   1140     operator<<(basic_ostream<char>&, const string&);
   1141   extern template
   1142     basic_istream<char>&
   1143     getline(basic_istream<char>&, string&, char);
   1144   extern template
   1145     basic_istream<char>&
   1146     getline(basic_istream<char>&, string&);
   1147 
   1148 #ifdef _GLIBCXX_USE_WCHAR_T
   1149   extern template class basic_string<wchar_t>;
   1150   extern template
   1151     basic_istream<wchar_t>&
   1152     operator>>(basic_istream<wchar_t>&, wstring&);
   1153   extern template
   1154     basic_ostream<wchar_t>&
   1155     operator<<(basic_ostream<wchar_t>&, const wstring&);
   1156   extern template
   1157     basic_istream<wchar_t>&
   1158     getline(basic_istream<wchar_t>&, wstring&, wchar_t);
   1159   extern template
   1160     basic_istream<wchar_t>&
   1161     getline(basic_istream<wchar_t>&, wstring&);
   1162 #endif
   1163 #endif
   1164 
   1165 _GLIBCXX_END_NAMESPACE_VERSION
   1166 } // namespace std
   1167 
   1168 #endif
   1169