libstdc++-v3/src/c++11/sso_string.cc

   1 // Helper for accessing __cxx11::string from the ABI -*- C++ -*-
   2
   3 // Copyright (C) 2014-2017 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25
  26 #define _GLIBCXX_USE_CXX11_ABI 1
  27 #define __sso_string __sso_stringxxx
  28 #include <string>
  29 #include <stdexcept>
  30 #undef __sso_string
  31
  32 #if ! _GLIBCXX_USE_DUAL_ABI
  33 # error This file should not be compiled for this configuration.
  34 #endif
  35
  36 namespace std _GLIBCXX_VISIBILITY(default)
  37 {
  38 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  39
  40 #pragma GCC diagnostic push
  41 #pragma GCC diagnostic ignored "-Wabi-tag"
  42   // Redefine __sso_string so that we can define and export its members
  43   // in terms of the SSO std::string.
  44   struct __sso_string
  45   {
  46     struct __str
  47     {
  48       const char* _M_p;
  49       size_t _M_string_length;
  50       char _M_local_buf[16];
  51     };
  52
  53     union {
  54       __str _M_s;
  55       char _M_bytes[sizeof(_M_s)];
  56       std::string _M_str;
  57     };
  58
  59     __sso_string();
  60     __sso_string(const std::string& s);
  61     __sso_string(const char*, size_t n);
  62     __sso_string(const __sso_string&) noexcept;
  63     __sso_string& operator=(const __sso_string&) noexcept;
  64     ~__sso_string();
  65     __sso_string(__sso_string&&) noexcept;
  66     __sso_string& operator=(__sso_string&&) noexcept;
  67   };
  68 #pragma GCC diagnostic pop
  69
  70   __sso_string::__sso_string() : _M_str() { }
  71
  72 #if _GLIBCXX_USE_CXX11_ABI
  73   static_assert(sizeof(__sso_string) == sizeof(std::string),
  74                 "sizeof(std::string) has changed");
  75   static_assert(alignof(__sso_string) == alignof(std::string),
  76                 "alignof(std::string) has changed");
  77
  78   // This constructor is defined in src/c++11/cow-stdexcept.cc for COW strings
  79   __sso_string::__sso_string(const std::string& s) : _M_str(s) { }
  80 #endif
  81
  82   __sso_string::__sso_string(const char* s, size_t n) : _M_str(s, n) { }
  83
  84   __sso_string::__sso_string(const __sso_string& s) noexcept
  85   : _M_str(s._M_str) { }
  86
  87   __sso_string&
  88   __sso_string::operator=(const __sso_string& s) noexcept
  89   {
  90     _M_str = s._M_str;
  91     return *this;
  92   }
  93
  94   __sso_string::~__sso_string() { _M_str.~basic_string(); }
  95
  96   __sso_string::__sso_string(__sso_string&& s) noexcept
  97   : _M_str(std::move(s._M_str)) { }
  98
  99   __sso_string&
 100   __sso_string::operator=(__sso_string&& s) noexcept
 101   {
 102     _M_str = std::move(s._M_str);
 103     return *this;
 104   }
 105
 106 _GLIBCXX_END_NAMESPACE_VERSION
 107 } // namespace