libstdc++-v3/libsupc++/new_opa.cc

   1 // Support routines for the -*- C++ -*- dynamic memory management.
   2
   3 // Copyright (C) 1997-2024 Free Software Foundation, Inc.
   4 //
   5 // This file is part of GCC.
   6 //
   7 // GCC is free software; you can redistribute it and/or modify
   8 // it under the terms of the GNU General Public License as published by
   9 // the Free Software Foundation; either version 3, or (at your option)
  10 // any later version.
  11 //
  12 // GCC is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16 //
  17 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 #include <bits/c++config.h>
  27 #include <stdlib.h>
  28 #include <stdint.h>
  29 #include <bit>
  30 #include "new"
  31
  32 #if !_GLIBCXX_HAVE_ALIGNED_ALLOC && !_GLIBCXX_HAVE__ALIGNED_MALLOC \
  33   && !_GLIBCXX_HAVE_POSIX_MEMALIGN && _GLIBCXX_HAVE_MEMALIGN
  34 # if _GLIBCXX_HOSTED && __has_include(<malloc.h>)
  35 // Some C libraries declare memalign in <malloc.h>
  36 #  include <malloc.h>
  37 # else
  38 extern "C" void *memalign(std::size_t boundary, std::size_t size);
  39 # endif
  40 #endif
  41
  42 using std::new_handler;
  43 using std::bad_alloc;
  44
  45 #if ! _GLIBCXX_HOSTED
  46 using std::size_t;
  47 extern "C"
  48 {
  49 # if _GLIBCXX_HAVE_POSIX_MEMALIGN
  50   void *posix_memalign(void **, size_t alignment, size_t size);
  51 # elif _GLIBCXX_HAVE_ALIGNED_ALLOC
  52   void *aligned_alloc(size_t alignment, size_t size);
  53 # elif _GLIBCXX_HAVE__ALIGNED_MALLOC
  54   void *_aligned_malloc(size_t size, size_t alignment);
  55 # elif _GLIBCXX_HAVE_MEMALIGN
  56   void *memalign(size_t alignment, size_t size);
  57 # else
  58   // A freestanding C runtime may not provide "malloc" -- but there is no
  59   // other reasonable way to implement "operator new".
  60   void *malloc(size_t);
  61 # endif
  62 }
  63 #endif
  64
  65 namespace __gnu_cxx {
  66 // Prefer posix_memalign if available, because it's older than aligned_alloc
  67 // and so more likely to be provided by replacement malloc libraries that
  68 // predate the addition of aligned_alloc. See PR libstdc++/113258.
  69 #if _GLIBCXX_HAVE_POSIX_MEMALIGN
  70 static inline void*
  71 aligned_alloc (std::size_t al, std::size_t sz)
  72 {
  73   void *ptr;
  74   // posix_memalign has additional requirement, not present on aligned_alloc:
  75   // The value of alignment shall be a power of two multiple of sizeof(void *).
  76   if (al < sizeof(void*))
  77     al = sizeof(void*);
  78   int ret = posix_memalign (&ptr, al, sz);
  79   if (ret == 0)
  80     return ptr;
  81   return nullptr;
  82 }
  83 #elif _GLIBCXX_HAVE_ALIGNED_ALLOC
  84 using ::aligned_alloc;
  85 #elif _GLIBCXX_HAVE__ALIGNED_MALLOC
  86 static inline void*
  87 aligned_alloc (std::size_t al, std::size_t sz)
  88 { return _aligned_malloc(sz, al); }
  89 #elif _GLIBCXX_HAVE_MEMALIGN
  90 static inline void*
  91 aligned_alloc (std::size_t al, std::size_t sz)
  92 {
  93   // Solaris requires al >= sizeof a word and QNX requires >= sizeof(void*)
  94   // but they both provide posix_memalign, so will use the definition above.
  95   return memalign (al, sz);
  96 }
  97 #else // !HAVE__ALIGNED_MALLOC && !HAVE_POSIX_MEMALIGN && !HAVE_MEMALIGN
  98 // The C library doesn't provide any aligned allocation functions, define one.
  99 // This is a modified version of code from gcc/config/i386/gmm_malloc.h
 100 static inline void*
 101 aligned_alloc (std::size_t al, std::size_t sz)
 102 {
 103   // We need extra bytes to store the original value returned by malloc.
 104   if (al < sizeof(void*))
 105     al = sizeof(void*);
 106   void* const malloc_ptr = malloc(sz + al);
 107   if (!malloc_ptr)
 108     return nullptr;
 109   // Align to the requested value, leaving room for the original malloc value.
 110   void* const aligned_ptr = (void *) (((uintptr_t) malloc_ptr + al) & -al);
 111
 112   // Store the original malloc value where it can be found by operator delete.
 113   ((void **) aligned_ptr)[-1] = malloc_ptr;
 114
 115   return aligned_ptr;
 116 }
 117 #endif
 118 } // namespace __gnu_cxx
 119
 120 _GLIBCXX_WEAK_DEFINITION void *
 121 operator new (std::size_t sz, std::align_val_t al)
 122 {
 123   std::size_t align = (std::size_t)al;
 124
 125   /* Alignment must be a power of two.  */
 126   /* XXX This should be checked by the compiler (PR 86878).  */
 127   if (__builtin_expect (!std::__has_single_bit(align), false))
 128     _GLIBCXX_THROW_OR_ABORT(bad_alloc());
 129
 130   /* malloc (0) is unpredictable; avoid it.  */
 131   if (__builtin_expect (sz == 0, false))
 132     sz = 1;
 133
 134 #if _GLIBCXX_HAVE_POSIX_MEMALIGN
 135 #elif _GLIBCXX_HAVE_ALIGNED_ALLOC
 136 # if defined _AIX || defined __APPLE__
 137   /* AIX 7.2.0.0 aligned_alloc incorrectly has posix_memalign's requirement
 138    * that alignment is a multiple of sizeof(void*).
 139    * OS X 10.15 has the same requirement.  */
 140   if (align < sizeof(void*))
 141     align = sizeof(void*);
 142 # endif
 143   /* C11: the value of size shall be an integral multiple of alignment.  */
 144   sz = (sz + align - 1) & ~(align - 1);
 145 #endif
 146
 147   void *p;
 148
 149   while ((p = __gnu_cxx::aligned_alloc (align, sz)) == nullptr)
 150     {
 151       new_handler handler = std::get_new_handler ();
 152       if (! handler)
 153         _GLIBCXX_THROW_OR_ABORT(bad_alloc());
 154       handler ();
 155     }
 156
 157   return p;
 158 }