MySQL  8.0.27
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malloc_allocator.h
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22 
23 #ifndef MALLOC_ALLOCATOR_INCLUDED
24 #define MALLOC_ALLOCATOR_INCLUDED
25 
26 #include <assert.h>
27 #include <limits>
28 #include <new>
29 #include <utility> // std::forward
30 
31 #include "my_sys.h"
33 #include "sql/psi_memory_key.h"
34 
35 /**
36  Malloc_allocator is a C++ STL memory allocator based on my_malloc/my_free.
37 
38  This allows for P_S instrumentation of memory allocation done by
39  internally by STL container classes.
40 
41  Example usage:
42  vector<int, Malloc_allocator<int>>
43  v((Malloc_allocator<int>(PSI_NOT_INSTRUMENTED)));
44 
45  If the type is complicated, you can just write Malloc_allocator<>(psi_key)
46  as a shorthand for Malloc_allocator<My_complicated_type>(psi_key), as all
47  Malloc_allocator instances are implicitly convertible to each other
48  and there is a default template parameter.
49 
50  @note allocate() throws std::bad_alloc() similarly to the default
51  STL memory allocator. This is necessary - STL functions which allocates
52  memory expects it. Otherwise these functions will try to use the memory,
53  leading to segfaults if memory allocation was not successful.
54 
55  @note This allocator cannot be used for std::basic_string with RHEL 6/7
56  because of this bug:
57  https://bugzilla.redhat.com/show_bug.cgi?id=1546704
58  "Define _GLIBCXX_USE_CXX11_ABI gets ignored by gcc in devtoolset-7"
59 */
60 
61 template <class T = void *>
63  // This cannot be const if we want to be able to swap.
65 
66  public:
67  typedef T value_type;
68  typedef size_t size_type;
69  typedef ptrdiff_t difference_type;
70 
71  typedef T *pointer;
72  typedef const T *const_pointer;
73 
74  typedef T &reference;
75  typedef const T &const_reference;
76 
77  pointer address(reference r) const { return &r; }
78  const_pointer address(const_reference r) const { return &r; }
79 
81 
82  template <class U>
83  Malloc_allocator(const Malloc_allocator<U> &other [[maybe_unused]])
84  : m_key(other.psi_key()) {}
85 
86  template <class U>
88  [[maybe_unused]]) {
89  assert(m_key == other.psi_key()); // Don't swap key.
90  }
91 
92  pointer allocate(size_type n, const_pointer hint [[maybe_unused]] = nullptr) {
93  if (n == 0) return nullptr;
94  if (n > max_size()) throw std::bad_alloc();
95 
96  pointer p = static_cast<pointer>(
97  my_malloc(m_key, n * sizeof(T), MYF(MY_WME | ME_FATALERROR)));
98  if (p == nullptr) throw std::bad_alloc();
99  return p;
100  }
101 
103 
104  template <class U, class... Args>
105  void construct(U *p, Args &&... args) {
106  assert(p != nullptr);
107  try {
108  ::new ((void *)p) U(std::forward<Args>(args)...);
109  } catch (...) {
110  assert(false); // Constructor should not throw an exception.
111  }
112  }
113 
114  void destroy(pointer p) {
115  assert(p != nullptr);
116  try {
117  p->~T();
118  } catch (...) {
119  assert(false); // Destructor should not throw an exception
120  }
121  }
122 
123  size_type max_size() const {
124  return std::numeric_limits<size_t>::max() / sizeof(T);
125  }
126 
127  template <class U>
128  struct rebind {
130  };
131 
132  PSI_memory_key psi_key() const { return m_key; }
133 };
134 
135 template <class T>
137  return a1.psi_key() == a2.psi_key();
138 }
139 
140 template <class T>
142  return a1.psi_key() != a2.psi_key();
143 }
144 
145 #endif // MALLOC_ALLOCATOR_INCLUDED
Malloc_allocator is a C++ STL memory allocator based on my_malloc/my_free.
Definition: malloc_allocator.h:62
Malloc_allocator(const Malloc_allocator< U > &other[[maybe_unused]])
Definition: malloc_allocator.h:83
size_t size_type
Definition: malloc_allocator.h:68
void construct(U *p, Args &&... args)
Definition: malloc_allocator.h:105
size_type max_size() const
Definition: malloc_allocator.h:123
PSI_memory_key psi_key() const
Definition: malloc_allocator.h:132
T & reference
Definition: malloc_allocator.h:74
const_pointer address(const_reference r) const
Definition: malloc_allocator.h:78
T value_type
Definition: malloc_allocator.h:67
pointer address(reference r) const
Definition: malloc_allocator.h:77
void deallocate(pointer p, size_type)
Definition: malloc_allocator.h:102
Malloc_allocator & operator=(const Malloc_allocator< U > &other[[maybe_unused]])
Definition: malloc_allocator.h:87
void destroy(pointer p)
Definition: malloc_allocator.h:114
PSI_memory_key m_key
Definition: malloc_allocator.h:64
const T * const_pointer
Definition: malloc_allocator.h:72
T * pointer
Definition: malloc_allocator.h:71
pointer allocate(size_type n, const_pointer hint[[maybe_unused]]=nullptr)
Definition: malloc_allocator.h:92
ptrdiff_t difference_type
Definition: malloc_allocator.h:69
Malloc_allocator(PSI_memory_key key)
Definition: malloc_allocator.h:80
const T & const_reference
Definition: malloc_allocator.h:75
const char * p
Definition: ctype-mb.cc:1236
#define U
Definition: ctype-tis620.cc:74
#define ME_FATALERROR
Definition: my_sys.h:151
#define MY_WME
Definition: my_sys.h:122
unsigned int PSI_memory_key
Instrumented memory key.
Definition: psi_memory_bits.h:48
bool operator==(const Malloc_allocator< T > &a1, const Malloc_allocator< T > &a2)
Definition: malloc_allocator.h:136
bool operator!=(const Malloc_allocator< T > &a1, const Malloc_allocator< T > &a2)
Definition: malloc_allocator.h:141
#define MYF(v)
Definition: my_inttypes.h:96
void my_free(void *ptr)
Frees the memory pointed by the ptr.
Definition: my_memory.cc:80
void * my_malloc(PSI_memory_key key, size_t size, int flags)
Allocates size bytes of memory.
Definition: my_memory.cc:56
Common header for many mysys elements.
const mysql_service_registry_t * r
Definition: pfs_example_plugin_employee.cc:85
required string key
Definition: replication_asynchronous_connection_failover.proto:59
Definition: malloc_allocator.h:128
Malloc_allocator< U > other
Definition: malloc_allocator.h:129
Definition: dtoa.cc:594
int n
Definition: xcom_base.cc:505