libc/src/__support/CPP/new.h

   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 class AllocChecker {
  33   bool success = false;
  34
  35   LIBC_INLINE AllocChecker &operator=(bool status) {
  36     success = status;
  37     return *this;
  38   }
  39
  40 public:
  41   LIBC_INLINE AllocChecker() = default;
  42
  43   LIBC_INLINE operator bool() const { return success; }
  44
  45   LIBC_INLINE static void *alloc(size_t s, AllocChecker &ac) {
  46     void *mem = ::malloc(s);
  47     ac = (mem != nullptr);
  48     return mem;
  49   }
  50
  51   LIBC_INLINE static void *aligned_alloc(size_t s, std::align_val_t align,
  52                                          AllocChecker &ac) {
  53 #ifdef LIBC_TARGET_OS_IS_WINDOWS
  54     // std::aligned_alloc is not available on Windows because std::free on
  55     // Windows cannot deallocate any over-aligned memory. Microsoft provides an
  56     // alternative for std::aligned_alloc named _aligned_malloc, but it must be
  57     // paired with _aligned_free instead of std::free.
  58     void *mem = ::_aligned_malloc(static_cast<size_t>(align), s);
  59 #else
  60     void *mem = ::aligned_alloc(static_cast<size_t>(align), s);
  61 #endif
  62     ac = (mem != nullptr);
  63     return mem;
  64   }
  65 };
  66
  67 } // namespace LIBC_NAMESPACE_DECL
  68
  69 LIBC_INLINE void *operator new(size_t size,
  70                                LIBC_NAMESPACE::AllocChecker &ac) noexcept {
  71   return LIBC_NAMESPACE::AllocChecker::alloc(size, ac);
  72 }
  73
  74 LIBC_INLINE void *operator new(size_t size, std::align_val_t align,
  75                                LIBC_NAMESPACE::AllocChecker &ac) noexcept {
  76   return LIBC_NAMESPACE::AllocChecker::aligned_alloc(size, align, ac);
  77 }
  78
  79 LIBC_INLINE void *operator new[](size_t size,
  80                                  LIBC_NAMESPACE::AllocChecker &ac) noexcept {
  81   return LIBC_NAMESPACE::AllocChecker::alloc(size, ac);
  82 }
  83
  84 LIBC_INLINE void *operator new[](size_t size, std::align_val_t align,
  85                                  LIBC_NAMESPACE::AllocChecker &ac) noexcept {
  86   return LIBC_NAMESPACE::AllocChecker::aligned_alloc(size, align, ac);
  87 }
  88
  89 LIBC_INLINE void *operator new(size_t, void *p) { return p; }
  90
  91 LIBC_INLINE void *operator new[](size_t, void *p) { return p; }
  92
  93 // The ideal situation would be to define the various flavors of operator delete
  94 // inlinelike we do with operator new above. However, since we need operator
  95 // delete prototypes to match those specified by the C++ standard, we cannot
  96 // define them inline as the C++ standard does not allow inline definitions of
  97 // replacement operator delete implementations. Note also that we assign a
  98 // special linkage name to each of these replacement operator delete functions.
  99 // This is because, if we do not give them a special libc internal linkage name,
 100 // they will replace operator delete for the entire application. Including this
 101 // header file in all libc source files where operator delete is called ensures
 102 // that only libc call sites use these replacement operator delete functions.
 103
 104 #define DELETE_NAME(name)                                                      \
 105   __asm__(LIBC_MACRO_TO_STRING(LIBC_NAMESPACE) "_" LIBC_MACRO_TO_STRING(name))
 106
 107 void operator delete(void *) noexcept DELETE_NAME(delete);
 108 void operator delete(void *, std::align_val_t) noexcept
 109     DELETE_NAME(delete_aligned);
 110 void operator delete(void *, size_t) noexcept DELETE_NAME(delete_sized);
 111 void operator delete(void *, size_t, std::align_val_t) noexcept
 112     DELETE_NAME(delete_sized_aligned);
 113 void operator delete[](void *) noexcept DELETE_NAME(delete_array);
 114 void operator delete[](void *, std::align_val_t) noexcept
 115     DELETE_NAME(delete_array_aligned);
 116 void operator delete[](void *, size_t) noexcept DELETE_NAME(delete_array_sized);
 117 void operator delete[](void *, size_t, std::align_val_t) noexcept
 118     DELETE_NAME(delete_array_sized_aligned);
 119
 120 #undef DELETE_NAME
 121
 122 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_NEW_H