libstdc++-v3/libsupc++/new

// The -*- C++ -*- dynamic memory management header.

// Copyright (C) 1994-2025 Free Software Foundation, Inc.

// This file is part of GCC.
//
// GCC 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 3, or (at your option)
// any later version.
// 
// GCC 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.
// 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file new
 *  This is a Standard C++ Library header.
 *
 *  The header @c new defines several functions to manage dynamic memory and
 *  handling memory allocation errors; see
 *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/dynamic_memory.html
 *  for more.
 */

#ifndef _NEW
#define _NEW

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/c++config.h>
#include <bits/exception.h>

#define __glibcxx_want_launder
#define __glibcxx_want_hardware_interference_size
#define __glibcxx_want_destroying_delete
#define __glibcxx_want_constexpr_new
#include <bits/version.h>

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++11-extensions" // scoped enum

#pragma GCC visibility push(default)

extern "C++" {

namespace std 
{
  /**
   *  @brief  Exception possibly thrown by @c new.
   *  @ingroup exceptions
   *
   *  @c bad_alloc (or classes derived from it) is used to report allocation
   *  errors from the throwing forms of @c new.  */
  class bad_alloc : public exception
  {
  public:
    bad_alloc() throw() { }

#if __cplusplus >= 201103L
    bad_alloc(const bad_alloc&) = default;
    bad_alloc& operator=(const bad_alloc&) = default;
#endif

    // This declaration is not useless:
    // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
    virtual ~bad_alloc() throw();

    // See comment in eh_exception.cc.
    virtual const char* what() const throw();
  };

#if __cplusplus >= 201103L
  class bad_array_new_length : public bad_alloc
  {
  public:
    bad_array_new_length() throw() { }

    // This declaration is not useless:
    // http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_6.html#SEC118
    virtual ~bad_array_new_length() throw();

    // See comment in eh_exception.cc.
    virtual const char* what() const throw();
  };
#endif

#if __cpp_aligned_new
  enum class align_val_t: size_t {};
#endif

  struct nothrow_t
  {
#if __cplusplus >= 201103L
    explicit nothrow_t() = default;
#endif
  };

  extern const nothrow_t nothrow;

  /** If you write your own error handler to be called by @c new, it must
   *  be of this type.  */
  typedef void (*new_handler)();

  /// Takes a replacement handler as the argument, returns the
  /// previous handler.
  new_handler set_new_handler(new_handler) throw();

#if __cplusplus >= 201103L
  /// Return the current new handler.
  new_handler get_new_handler() noexcept;
#endif
} // namespace std

//@{
/** These are replaceable signatures:
 *  - normal single new and delete (no arguments, throw @c bad_alloc on error)
 *  - normal array new and delete (same)
 *  - @c nothrow single new and delete (take a @c nothrow argument, return
 *    @c NULL on error)
 *  - @c nothrow array new and delete (same)
 *
 *  Placement new and delete signatures (take a memory address argument,
 *  does nothing) may not be replaced by a user's program.
*/
_GLIBCXX_NODISCARD void* operator new(std::size_t)
  _GLIBCXX_TXN_SAFE _GLIBCXX_THROW (std::bad_alloc)
  __attribute__((__externally_visible__, __malloc__));
_GLIBCXX_NODISCARD void* operator new[](std::size_t)
  _GLIBCXX_TXN_SAFE _GLIBCXX_THROW (std::bad_alloc)
  __attribute__((__externally_visible__, __malloc__));
void operator delete(void*) _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
void operator delete[](void*) _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
#if __cpp_sized_deallocation
void operator delete(void*, std::size_t)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
void operator delete[](void*, std::size_t)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
#endif
_GLIBCXX_NODISCARD void* operator new(std::size_t, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__, __alloc_size__ (1), __malloc__));
_GLIBCXX_NODISCARD void* operator new[](std::size_t, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__, __alloc_size__ (1), __malloc__));
void operator delete(void*, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
void operator delete[](void*, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__));
#if __cpp_aligned_new
_GLIBCXX_NODISCARD void* operator new(std::size_t, std::align_val_t)
  _GLIBCXX_TXN_SAFE
  __attribute__((__externally_visible__, __alloc_size__ (1), __alloc_align__ (2),  __malloc__));
_GLIBCXX_NODISCARD void* operator new(std::size_t, std::align_val_t, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__, __alloc_size__ (1), __alloc_align__ (2), __malloc__));
void operator delete(void*, std::align_val_t) _GLIBCXX_TXN_SAFE
  _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
void operator delete(void*, std::align_val_t, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE
  _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
_GLIBCXX_NODISCARD void* operator new[](std::size_t, std::align_val_t)
  _GLIBCXX_TXN_SAFE
  __attribute__((__externally_visible__, __alloc_size__ (1), __alloc_align__ (2), __malloc__));
_GLIBCXX_NODISCARD void* operator new[](std::size_t, std::align_val_t, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
  __attribute__((__externally_visible__, __alloc_size__ (1), __alloc_align__ (2), __malloc__));
void operator delete[](void*, std::align_val_t) _GLIBCXX_TXN_SAFE
  _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
void operator delete[](void*, std::align_val_t, const std::nothrow_t&)
  _GLIBCXX_TXN_SAFE
  _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
#if __cpp_sized_deallocation
void operator delete(void*, std::size_t, std::align_val_t) _GLIBCXX_TXN_SAFE
  _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
void operator delete[](void*, std::size_t, std::align_val_t) _GLIBCXX_TXN_SAFE
  _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
#endif // __cpp_sized_deallocation
#endif // __cpp_aligned_new

#if __cpp_lib_constexpr_new >= 202406L
# define _GLIBCXX_PLACEMENT_CONSTEXPR constexpr
#else
# define _GLIBCXX_PLACEMENT_CONSTEXPR inline
#endif

// Default placement versions of operator new.
_GLIBCXX_NODISCARD _GLIBCXX_PLACEMENT_CONSTEXPR
void* operator new(std::size_t, void* __p)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
{ return __p; }
_GLIBCXX_NODISCARD _GLIBCXX_PLACEMENT_CONSTEXPR
void* operator new[](std::size_t, void* __p)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
{ return __p; }

#undef _GLIBCXX_PLACEMENT_CONSTEXPR

// Default placement versions of operator delete.
inline void operator delete  (void*, void*)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
{ }
inline void operator delete[](void*, void*)
  _GLIBCXX_TXN_SAFE _GLIBCXX_USE_NOEXCEPT
{ }
//@}
} // extern "C++"

namespace std
{
#ifdef __cpp_lib_launder // C++ >= 17 && HAVE_BUILTIN_LAUNDER
  /// Pointer optimization barrier [ptr.launder]
  template<typename _Tp>
    [[nodiscard]] constexpr _Tp*
    launder(_Tp* __p) noexcept
    {
      if constexpr (__is_same(const volatile _Tp, const volatile void))
	static_assert(!__is_same(const volatile _Tp, const volatile void),
		      "std::launder argument must not be a void pointer");
#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function)
      else if constexpr (__is_function(_Tp))
	static_assert(!__is_function(_Tp),
		      "std::launder argument must not be a function pointer");
#endif
      else
	return __builtin_launder(__p);
      return nullptr;
    }
#endif // __cpp_lib_launder

#ifdef __cpp_lib_hardware_interference_size // C++ >= 17 && defined(gcc_dest_sz)
  inline constexpr size_t hardware_destructive_interference_size = __GCC_DESTRUCTIVE_SIZE;
  inline constexpr size_t hardware_constructive_interference_size = __GCC_CONSTRUCTIVE_SIZE;
#endif // __cpp_lib_hardware_interference_size

// Emitted despite the FTM potentially being undefined.
#if __cplusplus >= 202002L
  /// Tag type used to declare a class-specific operator delete that can
  /// invoke the destructor before deallocating the memory.
  struct destroying_delete_t
  {
    explicit destroying_delete_t() = default;
  };
  /// Tag variable of type destroying_delete_t.
  inline constexpr destroying_delete_t destroying_delete{};
#endif // C++20
}

#pragma GCC visibility pop
#pragma GCC diagnostic pop

#endif