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| -rw-r--r-- | docs/CodingStandards.rst | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/docs/CodingStandards.rst b/docs/CodingStandards.rst index a416a1e856..bc58f57cb7 100644 --- a/docs/CodingStandards.rst +++ b/docs/CodingStandards.rst @@ -818,6 +818,34 @@ least one out-of-line virtual method in the class. Without this, the compiler will copy the vtable and RTTI into every ``.o`` file that ``#include``\s the header, bloating ``.o`` file sizes and increasing link times. +Use ``LLVM_DELETED_FUNCTION`` to mark uncallable methods +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Prior to C++11, a common pattern to make a class uncopyable was to declare an +unimplemented copy constructor and copy assignment operator and make them +private. This would give a compiler error for accessing a private method or a +linker error because it wasn't implemented. + +With C++11, we can mark methods that won't be implemented with ``= deleted``. +This will trigger a much better error message and tell the compiler that the +method will never be implemented. This enables other checks like +``-Wunused-private-field`` to run correctly on classes that contain these +methods. + +To maintain compatibility with C++03, ``LLVM_DELETED_FUNCTION`` should be used +which will expand to ``= deleted`` if the compiler supports it. These methods +should still be declared private. Example of the uncopyable pattern: + +.. code-block:: c++ + + class DontCopy { + private: + DontCopy(const DontCopy&) LLVM_DELETED_FUNCTION; + DontCopy &operator =(const DontCopy&) LLVM_DELETED_FUNCTION; + public: + ... + }; + Don't evaluate ``end()`` every time through a loop ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |