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Each pointer has a type it points to, but one can freely cast between pointer types (but not between a function pointer and an object pointer). A special pointer type called the “void pointer” allows pointing to any (non-function) object, but is limited by the fact that it cannot be dereferenced directly (it shall be cast).
C supports the use of pointers, a type of reference that records the address or location of an object or function in memory. Pointers can be dereferenced to access data stored at the address pointed to, or to invoke a pointed-to function. Pointers can be manipulated using assignment or pointer arithmetic. The run-time representation of a ...
When an object is created, a pointer to this table, called the virtual table pointer, vpointer or VPTR, is added as a hidden member of this object. As such, the compiler must also generate "hidden" code in the constructors of each class to initialize a new object's virtual table pointer to the address of its class's virtual method table.
In computer programming, run-time type information or run-time type identification (RTTI) [1] is a feature of some programming languages (such as C++, [2] Object Pascal, and Ada [3]) that exposes information about an object's data type at runtime. Run-time type information may be available for all types or only to types that explicitly have it ...
Specifically, C allows a void* pointer to be assigned to any pointer type without a cast, while C++ does not; this idiom appears often in C code using malloc memory allocation, [9] or in the passing of context pointers to the POSIX pthreads API, and other frameworks involving callbacks. For example, the following is valid in C but not C++:
In computer programming, an indirection (also called a reference) is a way of referring to something using a name, reference, or container instead of the value itself. The most common form of indirection is the act of manipulating a value through its memory address. For example, accessing a variable through the use of a pointer.
Fortran does not have an explicit representation of references, but does use them implicitly in its call-by-reference calling semantics. A Fortran reference is best thought of as an alias of another object, such as a scalar variable or a row or column of an array. There is no syntax to dereference the reference or manipulate the contents of the ...
We could use these 4 bits to mark the table entry with extra information. For example, bit 0 might mean read only, bit 1 might mean dirty (the table entry needs to be updated), and so on. If pointers are 16-bit values, then: 0x3421 is a read-only pointer to the table_entry at address 0x3420; 0xf472 is a pointer to a dirty table_entry at address ...