1 // Support routines for the -*- C++ -*- dynamic memory management.
2
3 // Copyright (C) 1997-2021 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_ALIGNED_ALLOC
50 void *aligned_alloc(size_t alignment, size_t size);
51 # elif _GLIBCXX_HAVE__ALIGNED_MALLOC
52 void *_aligned_malloc(size_t size, size_t alignment);
53 # elif _GLIBCXX_HAVE_POSIX_MEMALIGN
54 void *posix_memalign(void **, size_t alignment, size_t size);
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 #if _GLIBCXX_HAVE_ALIGNED_ALLOC
67 using ::aligned_alloc;
68 #elif _GLIBCXX_HAVE__ALIGNED_MALLOC
69 static inline void*
70 aligned_alloc (std::size_t al, std::size_t sz)
71 { return _aligned_malloc(sz, al); }
72 #elif _GLIBCXX_HAVE_POSIX_MEMALIGN
73 static inline void*
74 aligned_alloc (std::size_t al, std::size_t sz)
75 {
76 void *ptr;
77 // posix_memalign has additional requirement, not present on aligned_alloc:
78 // The value of alignment shall be a power of two multiple of sizeof(void *).
79 if (al < sizeof(void*))
80 al = sizeof(void*);
81 int ret = posix_memalign (&ptr, al, sz);
82 if (ret == 0)
83 return ptr;
84 return nullptr;
85 }
86 #elif _GLIBCXX_HAVE_MEMALIGN
87 static inline void*
88 aligned_alloc (std::size_t al, std::size_t sz)
89 {
90 return memalign (al, sz);
91 }
92 #else // !HAVE__ALIGNED_MALLOC && !HAVE_POSIX_MEMALIGN && !HAVE_MEMALIGN
93 // The C library doesn't provide any aligned allocation functions, define one.
94 // This is a modified version of code from gcc/config/i386/gmm_malloc.h
95 static inline void*
96 aligned_alloc (std::size_t al, std::size_t sz)
97 {
98 // We need extra bytes to store the original value returned by malloc.
99 if (al < sizeof(void*))
100 al = sizeof(void*);
101 void* const malloc_ptr = malloc(sz + al);
102 if (!malloc_ptr)
103 return nullptr;
104 // Align to the requested value, leaving room for the original malloc value.
105 void* const aligned_ptr = (void *) (((uintptr_t) malloc_ptr + al) & -al);
106
107 // Store the original malloc value where it can be found by operator delete.
108 ((void **) aligned_ptr)[-1] = malloc_ptr;
109
110 return aligned_ptr;
111 }
112 #endif
113 } // namespace __gnu_cxx
114
115 _GLIBCXX_WEAK_DEFINITION void *
operator new(std::size_t sz,std::align_val_t al)116 operator new (std::size_t sz, std::align_val_t al)
117 {
118 std::size_t align = (std::size_t)al;
119
120 /* Alignment must be a power of two. */
121 /* XXX This should be checked by the compiler (PR 86878). */
122 if (__builtin_expect (!std::__has_single_bit(align), false))
123 _GLIBCXX_THROW_OR_ABORT(bad_alloc());
124
125 /* malloc (0) is unpredictable; avoid it. */
126 if (__builtin_expect (sz == 0, false))
127 sz = 1;
128
129 #if _GLIBCXX_HAVE_ALIGNED_ALLOC
130 # if defined _AIX || defined __APPLE__
131 /* AIX 7.2.0.0 aligned_alloc incorrectly has posix_memalign's requirement
132 * that alignment is a multiple of sizeof(void*).
133 * OS X 10.15 has the same requirement. */
134 if (align < sizeof(void*))
135 align = sizeof(void*);
136 # endif
137 /* C11: the value of size shall be an integral multiple of alignment. */
138 sz = (sz + align - 1) & ~(align - 1);
139 #endif
140
141 void *p;
142
143 while ((p = __gnu_cxx::aligned_alloc (align, sz)) == nullptr)
144 {
145 new_handler handler = std::get_new_handler ();
146 if (! handler)
147 _GLIBCXX_THROW_OR_ABORT(bad_alloc());
148 handler ();
149 }
150
151 return p;
152 }
153