gcc/libstdc++-v3/config/locale/generic/c_locale.h

// Wrapper for underlying C-language localization -*- C++ -*-

// Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

//
// ISO C++ 14882: 22.8  Standard locale categories.
//

// Written by Benjamin Kosnik <bkoz@redhat.com>

#ifndef _C_LOCALE_H
#define _C_LOCALE_H 1

#pragma GCC system_header

#include <clocale>
#include <cstdlib>   // get std::malloc
#include <cstring>   // get std::strlen
#include <cstdio>    // get std::snprintf or std::sprintf

#define _GLIBCXX_NUM_CATEGORIES 0

namespace std
{
  typedef int*			__c_locale;

  // Convert numeric value of type _Tv to string and return length of
  // string.  If snprintf is available use it, otherwise fall back to
  // the unsafe sprintf which, in general, can be dangerous and should
  // be avoided.
  template<typename _Tv>
    int
    __convert_from_v(char* __out, 
		     const int __size __attribute__((__unused__)),
		     const char* __fmt,
		     _Tv __v, const __c_locale&, int __prec = -1)
    {
      char* __old = std::setlocale(LC_ALL, NULL);
      char* __sav = static_cast<char*>(std::malloc(std::strlen(__old) + 1));
      if (__sav)
        std::strcpy(__sav, __old);
      std::setlocale(LC_ALL, "C");

      int __ret;
#ifdef _GLIBCXX_USE_C99
      if (__prec >= 0)
        __ret = std::snprintf(__out, __size, __fmt, __prec, __v);
      else
        __ret = std::snprintf(__out, __size, __fmt, __v);
#else
      if (__prec >= 0)
        __ret = std::sprintf(__out, __fmt, __prec, __v);
      else
        __ret = std::sprintf(__out, __fmt, __v);
#endif
      std::setlocale(LC_ALL, __sav);
      std::free(__sav);
      return __ret;
    }
}

#endif