mbed library sources. Supersedes mbed-src.
Dependents: Nucleo_Hello_Encoder BLE_iBeaconScan AM1805_DEMO DISCO-F429ZI_ExportTemplate1 ... more
platform/NonCopyable.h@189:f392fc9709a3, 2019-02-20 (annotated)
- Committer:
- AnnaBridge
- Date:
- Wed Feb 20 22:31:08 2019 +0000
- Revision:
- 189:f392fc9709a3
- Parent:
- 188:bcfe06ba3d64
mbed library release version 165
Who changed what in which revision?
User | Revision | Line number | New contents of line |
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AnnaBridge | 168:9672193075cf | 1 | /* Copyright (c) 2017 ARM Limited |
AnnaBridge | 189:f392fc9709a3 | 2 | * SPDX-License-Identifier: Apache-2.0 |
AnnaBridge | 168:9672193075cf | 3 | * |
AnnaBridge | 168:9672193075cf | 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
AnnaBridge | 168:9672193075cf | 5 | * you may not use this file except in compliance with the License. |
AnnaBridge | 168:9672193075cf | 6 | * You may obtain a copy of the License at |
AnnaBridge | 168:9672193075cf | 7 | * |
AnnaBridge | 168:9672193075cf | 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
AnnaBridge | 168:9672193075cf | 9 | * |
AnnaBridge | 168:9672193075cf | 10 | * Unless required by applicable law or agreed to in writing, software |
AnnaBridge | 168:9672193075cf | 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
AnnaBridge | 168:9672193075cf | 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
AnnaBridge | 168:9672193075cf | 13 | * See the License for the specific language governing permissions and |
AnnaBridge | 168:9672193075cf | 14 | * limitations under the License. |
AnnaBridge | 168:9672193075cf | 15 | */ |
AnnaBridge | 168:9672193075cf | 16 | |
AnnaBridge | 168:9672193075cf | 17 | #ifndef MBED_NONCOPYABLE_H_ |
AnnaBridge | 168:9672193075cf | 18 | #define MBED_NONCOPYABLE_H_ |
AnnaBridge | 168:9672193075cf | 19 | |
Anna Bridge |
180:96ed750bd169 | 20 | #if (!defined(MBED_DEBUG) && (MBED_CONF_PLATFORM_FORCE_NON_COPYABLE_ERROR == 0)) |
Anna Bridge |
180:96ed750bd169 | 21 | #include "mbed_toolchain.h" |
Anna Bridge |
180:96ed750bd169 | 22 | #include "mbed_debug.h" |
Anna Bridge |
180:96ed750bd169 | 23 | #endif |
Anna Bridge |
180:96ed750bd169 | 24 | |
Anna Bridge |
180:96ed750bd169 | 25 | namespace mbed { |
AnnaBridge | 168:9672193075cf | 26 | |
AnnaBridge | 188:bcfe06ba3d64 | 27 | /** \addtogroup platform */ |
AnnaBridge | 188:bcfe06ba3d64 | 28 | /** @{*/ |
AnnaBridge | 168:9672193075cf | 29 | /** |
AnnaBridge | 188:bcfe06ba3d64 | 30 | * \defgroup platform_NonCopyable NonCopyable class |
AnnaBridge | 188:bcfe06ba3d64 | 31 | * @{ |
AnnaBridge | 188:bcfe06ba3d64 | 32 | */ |
AnnaBridge | 188:bcfe06ba3d64 | 33 | |
AnnaBridge | 188:bcfe06ba3d64 | 34 | /** |
AnnaBridge | 189:f392fc9709a3 | 35 | * Prevents generation of copy constructor and copy assignment operator in |
AnnaBridge | 188:bcfe06ba3d64 | 36 | * derived classes. |
AnnaBridge | 189:f392fc9709a3 | 37 | * |
AnnaBridge | 188:bcfe06ba3d64 | 38 | * @par Usage |
AnnaBridge | 189:f392fc9709a3 | 39 | * |
AnnaBridge | 189:f392fc9709a3 | 40 | * To prevent generation of copy constructor and copy assignment operator, |
AnnaBridge | 189:f392fc9709a3 | 41 | * inherit privately from the NonCopyable class. |
AnnaBridge | 189:f392fc9709a3 | 42 | * |
AnnaBridge | 189:f392fc9709a3 | 43 | * @code |
AnnaBridge | 188:bcfe06ba3d64 | 44 | * class Resource : NonCopyable<Resource> { }; |
AnnaBridge | 189:f392fc9709a3 | 45 | * |
AnnaBridge | 188:bcfe06ba3d64 | 46 | * Resource r; |
AnnaBridge | 188:bcfe06ba3d64 | 47 | * // generates compile time error: |
AnnaBridge | 188:bcfe06ba3d64 | 48 | * Resource r2 = r; |
AnnaBridge | 188:bcfe06ba3d64 | 49 | * @endcode |
AnnaBridge | 189:f392fc9709a3 | 50 | * |
AnnaBridge | 188:bcfe06ba3d64 | 51 | * @par Background information |
AnnaBridge | 189:f392fc9709a3 | 52 | * |
AnnaBridge | 189:f392fc9709a3 | 53 | * Instances of polymorphic classes are not meant to be copied. The |
AnnaBridge | 189:f392fc9709a3 | 54 | * C++ standards generate a default copy constructor and copy assignment |
AnnaBridge | 188:bcfe06ba3d64 | 55 | * function if these functions have not been defined in the class. |
AnnaBridge | 189:f392fc9709a3 | 56 | * |
AnnaBridge | 188:bcfe06ba3d64 | 57 | * Consider the following example: |
AnnaBridge | 189:f392fc9709a3 | 58 | * |
AnnaBridge | 168:9672193075cf | 59 | * @code |
AnnaBridge | 188:bcfe06ba3d64 | 60 | * // base class representing a connection |
AnnaBridge | 189:f392fc9709a3 | 61 | * struct Connection { |
AnnaBridge | 188:bcfe06ba3d64 | 62 | * Connection(); |
AnnaBridge | 188:bcfe06ba3d64 | 63 | * virtual ~Connection(); |
AnnaBridge | 188:bcfe06ba3d64 | 64 | * virtual void open() = 0; |
AnnaBridge | 188:bcfe06ba3d64 | 65 | * } |
AnnaBridge | 189:f392fc9709a3 | 66 | * |
AnnaBridge | 189:f392fc9709a3 | 67 | * class SerialConnection : public Connection { |
Anna Bridge |
180:96ed750bd169 | 68 | * public: |
AnnaBridge | 188:bcfe06ba3d64 | 69 | * SerialConnection(Serial*); |
AnnaBridge | 189:f392fc9709a3 | 70 | * |
AnnaBridge | 168:9672193075cf | 71 | * private: |
AnnaBridge | 188:bcfe06ba3d64 | 72 | * Serial* _serial; |
AnnaBridge | 188:bcfe06ba3d64 | 73 | * }; |
AnnaBridge | 189:f392fc9709a3 | 74 | * |
AnnaBridge | 189:f392fc9709a3 | 75 | * Connection& get_connection() { |
AnnaBridge | 188:bcfe06ba3d64 | 76 | * static SerialConnection serial_connection; |
AnnaBridge | 188:bcfe06ba3d64 | 77 | * return serial_connection; |
AnnaBridge | 168:9672193075cf | 78 | * } |
Anna Bridge |
180:96ed750bd169 | 79 | * |
AnnaBridge | 188:bcfe06ba3d64 | 80 | * Connection connection = get_connection(); |
Anna Bridge |
180:96ed750bd169 | 81 | * @endcode |
AnnaBridge | 189:f392fc9709a3 | 82 | * |
AnnaBridge | 189:f392fc9709a3 | 83 | * There is a subtle bug in this code, the function get_connection returns a |
AnnaBridge | 189:f392fc9709a3 | 84 | * reference to a Connection which is captured by value instead of reference. |
AnnaBridge | 189:f392fc9709a3 | 85 | * |
AnnaBridge | 189:f392fc9709a3 | 86 | * When `get_connection` returns a reference to serial_connection it is copied into |
AnnaBridge | 189:f392fc9709a3 | 87 | * the local variable connection. The vtable and others members defined in Connection |
AnnaBridge | 189:f392fc9709a3 | 88 | * are copied, but members defined in SerialConnection are left apart. This can cause |
AnnaBridge | 189:f392fc9709a3 | 89 | * severe crashes or bugs if the virtual functions captured use members not present |
AnnaBridge | 188:bcfe06ba3d64 | 90 | * in the base declaration. |
AnnaBridge | 189:f392fc9709a3 | 91 | * |
AnnaBridge | 189:f392fc9709a3 | 92 | * To solve that problem, the copy constructor and assignment operator have to |
AnnaBridge | 189:f392fc9709a3 | 93 | * be declared (but don't need to be defined) in the private section of the |
AnnaBridge | 188:bcfe06ba3d64 | 94 | * Connection class: |
AnnaBridge | 189:f392fc9709a3 | 95 | * |
Anna Bridge |
180:96ed750bd169 | 96 | * @code |
AnnaBridge | 189:f392fc9709a3 | 97 | * struct Connection { |
AnnaBridge | 168:9672193075cf | 98 | * private: |
AnnaBridge | 188:bcfe06ba3d64 | 99 | * Connection(const Connection&); |
AnnaBridge | 188:bcfe06ba3d64 | 100 | * Connection& operator=(const Connection&); |
AnnaBridge | 168:9672193075cf | 101 | * } |
AnnaBridge | 168:9672193075cf | 102 | * @endcode |
AnnaBridge | 189:f392fc9709a3 | 103 | * |
AnnaBridge | 189:f392fc9709a3 | 104 | * Although manually declaring private copy constructor and assignment functions |
AnnaBridge | 189:f392fc9709a3 | 105 | * works, it is not ideal. These declarations are usually easy to forget, |
AnnaBridge | 188:bcfe06ba3d64 | 106 | * not immediately visible, and may be obscure to uninformed programmers. |
AnnaBridge | 189:f392fc9709a3 | 107 | * |
AnnaBridge | 189:f392fc9709a3 | 108 | * Using the NonCopyable class reduces the boilerplate required and expresses |
AnnaBridge | 188:bcfe06ba3d64 | 109 | * the intent because class inheritance appears right after the class name |
AnnaBridge | 188:bcfe06ba3d64 | 110 | * declaration. |
AnnaBridge | 189:f392fc9709a3 | 111 | * |
AnnaBridge | 188:bcfe06ba3d64 | 112 | * @code |
AnnaBridge | 189:f392fc9709a3 | 113 | * struct Connection : private NonCopyable<Connection> { |
AnnaBridge | 188:bcfe06ba3d64 | 114 | * // regular declarations |
AnnaBridge | 168:9672193075cf | 115 | * } |
AnnaBridge | 188:bcfe06ba3d64 | 116 | * @endcode |
AnnaBridge | 189:f392fc9709a3 | 117 | * |
AnnaBridge | 189:f392fc9709a3 | 118 | * |
AnnaBridge | 189:f392fc9709a3 | 119 | * @par Implementation details |
AnnaBridge | 189:f392fc9709a3 | 120 | * |
AnnaBridge | 189:f392fc9709a3 | 121 | * Using a template type prevents cases where the empty base optimization cannot |
AnnaBridge | 189:f392fc9709a3 | 122 | * be applied and therefore ensures that the cost of the NonCopyable semantic |
AnnaBridge | 188:bcfe06ba3d64 | 123 | * sugar is null. |
AnnaBridge | 189:f392fc9709a3 | 124 | * |
Anna Bridge |
180:96ed750bd169 | 125 | * As an example, the empty base optimization is prohibited if one of the empty |
AnnaBridge | 188:bcfe06ba3d64 | 126 | * base classes is also a base type of the first nonstatic data member: |
Anna Bridge |
180:96ed750bd169 | 127 | * |
Anna Bridge |
180:96ed750bd169 | 128 | * @code |
AnnaBridge | 168:9672193075cf | 129 | * struct A { }; |
Anna Bridge |
180:96ed750bd169 | 130 | * struct B : A { |
AnnaBridge | 168:9672193075cf | 131 | * int foo; |
AnnaBridge | 168:9672193075cf | 132 | * }; |
AnnaBridge | 168:9672193075cf | 133 | * // thanks to empty base optimization, sizeof(B) == sizeof(int) |
Anna Bridge |
180:96ed750bd169 | 134 | * |
Anna Bridge |
180:96ed750bd169 | 135 | * struct C : A { |
AnnaBridge | 168:9672193075cf | 136 | * B b; |
AnnaBridge | 168:9672193075cf | 137 | * }; |
Anna Bridge |
180:96ed750bd169 | 138 | * |
AnnaBridge | 168:9672193075cf | 139 | * // empty base optimization cannot be applied here because A from C and A from |
AnnaBridge | 188:bcfe06ba3d64 | 140 | * // B have a different address. In that case, with the alignment |
AnnaBridge | 168:9672193075cf | 141 | * // sizeof(C) == 2* sizeof(int) |
AnnaBridge | 168:9672193075cf | 142 | * @endcode |
Anna Bridge |
180:96ed750bd169 | 143 | * |
AnnaBridge | 188:bcfe06ba3d64 | 144 | * The solution to that problem is to templatize the empty class to make it |
Anna Bridge |
180:96ed750bd169 | 145 | * unique to the type it is applied to: |
Anna Bridge |
180:96ed750bd169 | 146 | * |
Anna Bridge |
180:96ed750bd169 | 147 | * @code |
AnnaBridge | 168:9672193075cf | 148 | * template<typename T> |
AnnaBridge | 168:9672193075cf | 149 | * struct A<T> { }; |
Anna Bridge |
180:96ed750bd169 | 150 | * struct B : A<B> { |
AnnaBridge | 168:9672193075cf | 151 | * int foo; |
AnnaBridge | 168:9672193075cf | 152 | * }; |
Anna Bridge |
180:96ed750bd169 | 153 | * struct C : A<C> { |
AnnaBridge | 168:9672193075cf | 154 | * B b; |
AnnaBridge | 168:9672193075cf | 155 | * }; |
Anna Bridge |
180:96ed750bd169 | 156 | * |
Anna Bridge |
180:96ed750bd169 | 157 | * // empty base optimization can be applied B and C does not refer to the same |
AnnaBridge | 168:9672193075cf | 158 | * // kind of A. sizeof(C) == sizeof(B) == sizeof(int). |
AnnaBridge | 168:9672193075cf | 159 | * @endcode |
Anna Bridge |
180:96ed750bd169 | 160 | * |
AnnaBridge | 189:f392fc9709a3 | 161 | * @tparam T The type that should be made noncopyable. |
AnnaBridge | 188:bcfe06ba3d64 | 162 | * |
AnnaBridge | 188:bcfe06ba3d64 | 163 | * @note Compile time errors are disabled if you use the develop or release profile. |
AnnaBridge | 188:bcfe06ba3d64 | 164 | * To override this behavior and force compile time errors in all profiles, |
Anna Bridge |
180:96ed750bd169 | 165 | * set the configuration parameter "platform.force-non-copyable-error" to true. |
AnnaBridge | 168:9672193075cf | 166 | */ |
AnnaBridge | 168:9672193075cf | 167 | template<typename T> |
Anna Bridge |
180:96ed750bd169 | 168 | class NonCopyable { |
AnnaBridge | 188:bcfe06ba3d64 | 169 | #ifndef DOXYGEN_ONLY |
AnnaBridge | 168:9672193075cf | 170 | protected: |
Anna Bridge |
180:96ed750bd169 | 171 | /** |
AnnaBridge | 184:08ed48f1de7f | 172 | * Disallow construction of NonCopyable objects from outside of its hierarchy. |
AnnaBridge | 168:9672193075cf | 173 | */ |
AnnaBridge | 168:9672193075cf | 174 | NonCopyable() { } |
Anna Bridge |
180:96ed750bd169 | 175 | /** |
AnnaBridge | 184:08ed48f1de7f | 176 | * Disallow destruction of NonCopyable objects from outside of its hierarchy. |
AnnaBridge | 168:9672193075cf | 177 | */ |
AnnaBridge | 168:9672193075cf | 178 | ~NonCopyable() { } |
AnnaBridge | 168:9672193075cf | 179 | |
Anna Bridge |
180:96ed750bd169 | 180 | #if (!defined(MBED_DEBUG) && (MBED_CONF_PLATFORM_FORCE_NON_COPYABLE_ERROR == 0)) |
Anna Bridge |
180:96ed750bd169 | 181 | /** |
Anna Bridge |
180:96ed750bd169 | 182 | * NonCopyable copy constructor. |
Anna Bridge |
180:96ed750bd169 | 183 | * |
AnnaBridge | 188:bcfe06ba3d64 | 184 | * A compile time warning is issued when this function is used, and a runtime |
AnnaBridge | 188:bcfe06ba3d64 | 185 | * warning is printed when the copy construction of the noncopyable happens. |
Anna Bridge |
180:96ed750bd169 | 186 | * |
Anna Bridge |
180:96ed750bd169 | 187 | * If you see this warning, your code is probably doing something unspecified. |
AnnaBridge | 188:bcfe06ba3d64 | 188 | * Copying of noncopyable resources can lead to resource leak and random error. |
Anna Bridge |
180:96ed750bd169 | 189 | */ |
Anna Bridge |
180:96ed750bd169 | 190 | MBED_DEPRECATED("Invalid copy construction of a NonCopyable resource.") |
AnnaBridge | 187:0387e8f68319 | 191 | NonCopyable(const NonCopyable &) |
Anna Bridge |
180:96ed750bd169 | 192 | { |
Anna Bridge |
180:96ed750bd169 | 193 | debug("Invalid copy construction of a NonCopyable resource: %s\r\n", MBED_PRETTY_FUNCTION); |
Anna Bridge |
180:96ed750bd169 | 194 | } |
Anna Bridge |
180:96ed750bd169 | 195 | |
AnnaBridge | 168:9672193075cf | 196 | /** |
Anna Bridge |
180:96ed750bd169 | 197 | * NonCopyable copy assignment operator. |
Anna Bridge |
180:96ed750bd169 | 198 | * |
AnnaBridge | 188:bcfe06ba3d64 | 199 | * A compile time warning is issued when this function is used, and a runtime |
AnnaBridge | 188:bcfe06ba3d64 | 200 | * warning is printed when the copy construction of the noncopyable happens. |
Anna Bridge |
180:96ed750bd169 | 201 | * |
Anna Bridge |
180:96ed750bd169 | 202 | * If you see this warning, your code is probably doing something unspecified. |
AnnaBridge | 188:bcfe06ba3d64 | 203 | * Copying of noncopyable resources can lead to resource leak and random error. |
Anna Bridge |
180:96ed750bd169 | 204 | */ |
Anna Bridge |
180:96ed750bd169 | 205 | MBED_DEPRECATED("Invalid copy assignment of a NonCopyable resource.") |
AnnaBridge | 187:0387e8f68319 | 206 | NonCopyable &operator=(const NonCopyable &) |
Anna Bridge |
180:96ed750bd169 | 207 | { |
Anna Bridge |
180:96ed750bd169 | 208 | debug("Invalid copy assignment of a NonCopyable resource: %s\r\n", MBED_PRETTY_FUNCTION); |
Anna Bridge |
180:96ed750bd169 | 209 | return *this; |
Anna Bridge |
180:96ed750bd169 | 210 | } |
Anna Bridge |
180:96ed750bd169 | 211 | |
Anna Bridge |
180:96ed750bd169 | 212 | #else |
Anna Bridge |
180:96ed750bd169 | 213 | private: |
Anna Bridge |
180:96ed750bd169 | 214 | /** |
AnnaBridge | 188:bcfe06ba3d64 | 215 | * Declare copy constructor as private. Any attempt to copy construct |
AnnaBridge | 168:9672193075cf | 216 | * a NonCopyable will fail at compile time. |
AnnaBridge | 168:9672193075cf | 217 | */ |
AnnaBridge | 187:0387e8f68319 | 218 | NonCopyable(const NonCopyable &); |
AnnaBridge | 168:9672193075cf | 219 | |
AnnaBridge | 168:9672193075cf | 220 | /** |
AnnaBridge | 188:bcfe06ba3d64 | 221 | * Declare copy assignment operator as private. Any attempt to copy assign |
AnnaBridge | 168:9672193075cf | 222 | * a NonCopyable will fail at compile time. |
AnnaBridge | 168:9672193075cf | 223 | */ |
AnnaBridge | 187:0387e8f68319 | 224 | NonCopyable &operator=(const NonCopyable &); |
Anna Bridge |
180:96ed750bd169 | 225 | #endif |
AnnaBridge | 189:f392fc9709a3 | 226 | #endif |
AnnaBridge | 168:9672193075cf | 227 | }; |
AnnaBridge | 168:9672193075cf | 228 | |
AnnaBridge | 188:bcfe06ba3d64 | 229 | /**@}*/ |
AnnaBridge | 188:bcfe06ba3d64 | 230 | |
AnnaBridge | 188:bcfe06ba3d64 | 231 | /**@}*/ |
AnnaBridge | 188:bcfe06ba3d64 | 232 | |
Anna Bridge |
180:96ed750bd169 | 233 | } // namespace mbed |
AnnaBridge | 168:9672193075cf | 234 | |
AnnaBridge | 168:9672193075cf | 235 | #endif /* MBED_NONCOPYABLE_H_ */ |