Defined Terms - allocator class
Standard library class that supports type-specific allocation of raw, unconstructed memory. The allocator class is a class template that defines member functions to allocate, deallocate, construct, and destroy objects of the allocator's template parameter type.
- anonymous union
Unnamed union that is not used to define an object. Members of the anonymous union are referred to directly. These unions may not have member functions and may not have private or protected members.
- bit-field
Class member with an signed or unsigned integral type that specifies the number of bits to allocate to the member. Bit-fields defined in consecutive order in the class are, if possible, compacted into a common integral value.
- delete expression
A delete expression destroys a dynamically allocated object of a specified type and frees the memory used by that object. A delete[] expression destroys the elements of a dynamically allocated array of a specified type and frees the memory used by the array. These expressions use the corresponding version of the library or class-specific operator delete functions to free raw memory that held the object or array.
- discriminant
Programming technique that uses an object to determine which actual type is held in a union at any given time.
- dynamic_cast
Operator that performs a checked cast from a base type to a derived type. The base type must define at least one virtual function. The operator checks the dynamic type of the object to which the reference or pointer is bound. If the object type is the same as the type of the cast (or a type derived from that type), then the cast is done. Otherwise, a zero pointer is returned for a pointer cast, or an exception is thrown for a cast of a reference.
- freelist
Memory management technique that involves preallocating unconstructed memory to hold objects that will be created as needed. When objects are freed, their memory is put back on the free list rather than being returned to the system.
- linkage directive
Mechanism used to allow functions written in a different language to be called from a C++ program. All compilers must support calling C and C++ functions. It is compiler-dependent whether any other languages are supported.
- local class
Class defined inside a function. A local class is visible only inside the function in which it is defined. All members of the class must be defined inside the class body. There can be no static members of a local class. Local class members may not access the local variables defined in the enclosing function. They may use type names, static variables, or enumerators defined in the enclosing function.
- member operators new and delete
Class member functions that override the default memory allocation performed by the global library operator new and operator delete functions. Both object (new) and array (new[]) forms of these functions may be defined. The member new and delete functions are implicitly declared as static. These operators allocate (deal-locate) memory. They are used automatically by new (delete) expressions, which handle object initialization and destruction.
- nested class
Class defined inside another class. A nested class is defined inside its enclosing scope: Nested-class names must be unique within the class scope in which they are defined but can be reused in scopes outside the enclosing class. Access to the nested class outside the enclosing class requires use of the scope operator to specify the scope(s) in which the class is nested.
- nested type
Synonym for nested class.
- new expression
A new expression allocates and constructs an object of a specified type. A new[] expression allocates and constructs an array of objects. These expressions use the corresponding version of the library operator new functions to allocate raw memory in which the expression constructs an object or array of the specified type.
- operator delete
A library function that frees untyped, unconstructed memory allocated by operator new. The library operator delete[] frees memory used to hold an array that was allocated by operator new[].
- operator new
A library function that allocates untyped, unconstructed memory of a given size. The library function operator new[] allocates raw memory for arrays. These library functions provide a more primitive allocation mechanism than the library allocator class. Modern C++ programs should use the allocator classes rather than these library functions.
- placement new expression
The form of new that constructs its object in specified memory. It does no allocation; instead, it takes an argument that specifies where the object should be constructed. It is a lower-level analog of the behavior provided by the construct member of the allocator class.
- pointer to member
Pointer that encapsulates the class type as well as the member type to which the pointer points. The definition of a pointer to member must specify the class name as well as the type of the member(s) to which the pointer may point: TC::*pmem = &C::member;
This statement defines pmem as a pointer that can point to members of the class named C that have type T and initializes it to point to the member in C named member. When the pointer is dereferenced, it must be bound to an object of or pointer to type C: classobj.*pmem; classptr->*pmem;
fetches member from the object classobj of the object pointed to by classptr.
- portable
Term used to describe a program that can be moved to a new machine with relatively little effort.
- run-time type identification
Term used to describe the language and library facilities that allow the dynamic type of a reference or pointer to be obtained at run time. The RTTI operators, typeid and dynamic_cast, provide the dynamic type only for references or pointers to class types with virtual functions. When applied to other types, the type returned is the static type of the reference or pointer.
- typeid
Unary operator that takes an expression and returns a reference to an object of the library type named type_info that describes the type of the expression. When the expression is an object of a type that has virtual functions, then the dynamic type of the expression is returned. If the type is a reference, pointer, or other type that does not define virtual functions, then the type returned is the static type of the reference, pointer, or object.
- type_info
Library type that describes a type. The type_info class is inherently machine-dependent, but any library must define type_info with members listed in Table 18.2 (p. 779). type_info objects may not be copied.
- union
Classlike aggregate type that may define multiple data members, only one of which can have a value at any one point. Members of a union must be simple types: They can be a built-in or compound type or a class type that does not define a constructor, destructor, or the assignment operator. Unions may have member functions, including constructors and destructors. A union may not serve as a base class.
- volatile
Type qualifier that signifies to the compiler that a variable might be changed outside the direct control of the program. It is a signal to the compiler that it may not perform certain optimizations.
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