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فرمت فایل: word (قابل ویرایش و آماده پرینت)
تعداد صفحات 37
C++ offers tremendous flexibility in managing memory, but few C++ programmers fully understand the available mechanisms. In this area of the language ,overloading , name hiding, constructors and destructors, exceptions, static and virtual functions, operator and non-operator functions all come together to provide great flexibility and customizability of memory management. Unfortunately, and perhaps unavoidably, things can also get a bit complex.
In this chapter, we’ll look at how the various features of C++ are used together in memory management, how they sometimes interact in surprising ways, and how to simplify their interactions.
Inasmuch as memory is just one of many resources a program manages, we’ll also look at how to bind other resources to memory so we can use C++’s sophisticated memory management facilities to manage other resources as well.
Failure to Distinguish Scalar and Array Allocation
Is a Widget the same thing as an array of Widgets? Of course not. Then why are so many C++ programmers surprised to find that different operators are used to allocate and free arrays and scalars?
We know how to allocate and free a single Widget. We use the new and delete operators:
Widget *w = new Widget( arg );
// . . .
delete w;
Unlike most operators in C++, the behavior of the new operator can’t be modified by overloading. The new operator always calls a function named operator new to obtain some storage, then may initialize that storage. In the case of Widget, above, use of the new operator will cause a call to an operator new function that takes a single argument of type size_t, then will invoke a Widget constructor on the uninitialized storage returned by operator new to produce a Widget object.
The delete operator invokes a destructor on the Widget and then calls a function named operator delete to deallocate the storage formerly occupied by the now deceased Widget object.
