1 // Support routines for the -*- C++ -*- dynamic memory management.
2
3 // Copyright (C) 1997-2022 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 int 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*
aligned_alloc(std::size_t al,std::size_t sz)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 *
operator new(std::size_t sz,std::align_val_t al)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 }
159