1 //===-- Libc specific custom operator new and delete ------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_NEW_H
10 #define LLVM_LIBC_SRC___SUPPORT_CPP_NEW_H
11
12 #include "hdr/func/aligned_alloc.h"
13 #include "hdr/func/free.h"
14 #include "hdr/func/malloc.h"
15 #include "src/__support/common.h"
16 #include "src/__support/macros/config.h"
17 #include "src/__support/macros/properties/os.h"
18
19 #include <stddef.h> // For size_t
20
21 // Defining members in the std namespace is not preferred. But, we do it here
22 // so that we can use it to define the operator new which takes std::align_val_t
23 // argument.
24 namespace std {
25
26 enum class align_val_t : size_t {};
27
28 } // namespace std
29
30 namespace LIBC_NAMESPACE_DECL {
31
32 namespace cpp {
launder(T * p)33 template <class T> [[nodiscard]] constexpr T *launder(T *p) {
34 static_assert(__has_builtin(__builtin_launder),
35 "cpp::launder requires __builtin_launder");
36 return __builtin_launder(p);
37 }
38 } // namespace cpp
39
40 class AllocChecker {
41 bool success = false;
42
43 LIBC_INLINE AllocChecker &operator=(bool status) {
44 success = status;
45 return *this;
46 }
47
48 public:
49 LIBC_INLINE AllocChecker() = default;
50
51 LIBC_INLINE operator bool() const { return success; }
52
alloc(size_t s,AllocChecker & ac)53 LIBC_INLINE static void *alloc(size_t s, AllocChecker &ac) {
54 void *mem = ::malloc(s);
55 ac = (mem != nullptr);
56 return mem;
57 }
58
aligned_alloc(size_t s,std::align_val_t align,AllocChecker & ac)59 LIBC_INLINE static void *aligned_alloc(size_t s, std::align_val_t align,
60 AllocChecker &ac) {
61 #ifdef LIBC_TARGET_OS_IS_WINDOWS
62 // std::aligned_alloc is not available on Windows because std::free on
63 // Windows cannot deallocate any over-aligned memory. Microsoft provides an
64 // alternative for std::aligned_alloc named _aligned_malloc, but it must be
65 // paired with _aligned_free instead of std::free.
66 void *mem = ::_aligned_malloc(static_cast<size_t>(align), s);
67 #else
68 void *mem = ::aligned_alloc(static_cast<size_t>(align), s);
69 #endif
70 ac = (mem != nullptr);
71 return mem;
72 }
73 };
74
75 } // namespace LIBC_NAMESPACE_DECL
76
new(size_t size,LIBC_NAMESPACE::AllocChecker & ac)77 LIBC_INLINE void *operator new(size_t size,
78 LIBC_NAMESPACE::AllocChecker &ac) noexcept {
79 return LIBC_NAMESPACE::AllocChecker::alloc(size, ac);
80 }
81
new(size_t size,std::align_val_t align,LIBC_NAMESPACE::AllocChecker & ac)82 LIBC_INLINE void *operator new(size_t size, std::align_val_t align,
83 LIBC_NAMESPACE::AllocChecker &ac) noexcept {
84 return LIBC_NAMESPACE::AllocChecker::aligned_alloc(size, align, ac);
85 }
86
87 LIBC_INLINE void *operator new[](size_t size,
88 LIBC_NAMESPACE::AllocChecker &ac) noexcept {
89 return LIBC_NAMESPACE::AllocChecker::alloc(size, ac);
90 }
91
92 LIBC_INLINE void *operator new[](size_t size, std::align_val_t align,
93 LIBC_NAMESPACE::AllocChecker &ac) noexcept {
94 return LIBC_NAMESPACE::AllocChecker::aligned_alloc(size, align, ac);
95 }
96
new(size_t,void * p)97 LIBC_INLINE void *operator new(size_t, void *p) { return p; }
98
99 LIBC_INLINE void *operator new[](size_t, void *p) { return p; }
100
101 // The ideal situation would be to define the various flavors of operator delete
102 // inlinelike we do with operator new above. However, since we need operator
103 // delete prototypes to match those specified by the C++ standard, we cannot
104 // define them inline as the C++ standard does not allow inline definitions of
105 // replacement operator delete implementations. Note also that we assign a
106 // special linkage name to each of these replacement operator delete functions.
107 // This is because, if we do not give them a special libc internal linkage name,
108 // they will replace operator delete for the entire application. Including this
109 // header file in all libc source files where operator delete is called ensures
110 // that only libc call sites use these replacement operator delete functions.
111
112 #define DELETE_NAME(name) \
113 __asm__(LIBC_MACRO_TO_STRING(LIBC_NAMESPACE) "_" LIBC_MACRO_TO_STRING(name))
114
115 void operator delete(void *) noexcept DELETE_NAME(delete);
116 void operator delete(void *, std::align_val_t) noexcept
117 DELETE_NAME(delete_aligned);
118 void operator delete(void *, size_t) noexcept DELETE_NAME(delete_sized);
119 void operator delete(void *, size_t, std::align_val_t) noexcept
120 DELETE_NAME(delete_sized_aligned);
121 void operator delete[](void *) noexcept DELETE_NAME(delete_array);
122 void operator delete[](void *, std::align_val_t) noexcept
123 DELETE_NAME(delete_array_aligned);
124 void operator delete[](void *, size_t) noexcept DELETE_NAME(delete_array_sized);
125 void operator delete[](void *, size_t, std::align_val_t) noexcept
126 DELETE_NAME(delete_array_sized_aligned);
127
128 #undef DELETE_NAME
129
130 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_NEW_H
131