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Java references are pointers to objects. [16] Java references do not allow direct access to memory addresses or allow memory addresses to be manipulated with pointer arithmetic. In C++ one can construct pointers to pointers, pointers to ints and doubles, and pointers to arbitrary memory locations.
The Boost C++ library provides strong and weak references. It is a mistake to use regular C++ pointers as the weak counterparts of smart pointers because such usage removes the ability to detect when the strong reference count has gone to 0 and the object has been deleted. Worse yet, it does not allow for detection of whether another strong ...
Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
Smart pointers can facilitate intentional programming by expressing, in the type, how the memory of the referent of the pointer will be managed. For example, if a C++ function returns a pointer, there is no way to know whether the caller should delete the memory of the referent when the caller is finished with the information.
Since C++11, the C++ standard library also provides smart pointers (unique_ptr, shared_ptr and weak_ptr) which can be used in some situations as a safer alternative to primitive C pointers. C++ also supports another form of reference, quite different from a pointer, called simply a reference or reference type.
Another frequent source of dangling pointers is a jumbled combination of malloc() and free() library calls: a pointer becomes dangling when the block of memory it points to is freed. As with the previous example one way to avoid this is to make sure to reset the pointer to null after freeing its reference—as demonstrated below.
A reference is an abstract data type and may be implemented in many ways. Typically, a reference refers to data stored in memory on a given system, and its internal value is the memory address of the data, i.e. a reference is implemented as a pointer. For this reason a reference is often said to "point to" the data.
Reference counting in C++ is usually implemented using "smart pointers" [19] whose constructors, destructors, and assignment operators manage the references. A smart pointer can be passed by reference to a function, which avoids the need to copy-construct a new smart pointer (which would increase the reference count on entry into the function ...