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There are several loopholes to pure const-correctness in C and C++. They exist primarily for compatibility with existing code. The first, which applies only to C++, is the use of const_cast, which allows the programmer to strip the const qualifier, making any object modifiable. The necessity of stripping the qualifier arises when using existing ...
immutable is a stronger variant of const, indicating data that can never change its value, while const indicates data that cannot be changed through this reference: it is a constant view on possibly mutable data. shared is used for shared data in multi-threading (as volatile was briefly used for in C++).
Although static_cast conversions are checked at compile time to prevent obvious incompatibilities, no run-time type checking is performed that would prevent a cast between incompatible data types, such as pointers. A static_cast from a pointer to a class B to a pointer to a derived class D is ill-formed if B is an inaccessible or ambiguous base ...
C++ is also more strict in conversions to enums: ints cannot be implicitly converted to enums as in C. Also, enumeration constants (enum enumerators) are always of type int in C, whereas they are distinct types in C++ and may have a size different from that of int. [needs update] In C++ a const variable must be initialized; in C this is not ...
Even functions can be const in C++. The meaning here is that only a const function may be called for an object instantiated as const; a const function doesn't change any non-mutable data. C# has both a const and a readonly qualifier; its const is only for compile-time constants, while readonly can be used in constructors and other runtime ...
In the C family of languages and ALGOL 68, the word cast typically refers to an explicit type conversion (as opposed to an implicit conversion), causing some ambiguity about whether this is a re-interpretation of a bit-pattern or a real data representation conversion. More important is the multitude of ways and rules that apply to what data ...
In C and C++, constructs such as pointer type conversion and union — C++ adds reference type conversion and reinterpret_cast to this list — are provided in order to permit many kinds of type punning, although some kinds are not actually supported by the standard language.
In class-based programming, downcasting, or type refinement, is the act of casting a base or parent class reference, to a more restricted derived class reference. [1] This is only allowable if the object is already an instance of the derived class, and so this conversion is inherently fallible.