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This can be understood as taking a null pointer of type structure st, and then obtaining the address of member m within said structure. While this implementation works correctly in many compilers, it has generated some debate regarding whether this is undefined behavior according to the C standard, [2] since it appears to involve a dereference of a null pointer (although, according to the ...
The final value of k is undefined. The answer that it must be 10 assumes that it started at zero, which may or may not be true. Note that in the example, the variable i is initialized to zero by the first clause of the for statement. Another example can be when dealing with structs.
C++ generally prohibits forward references, but they are allowed in the special case of class members. Since the member function accessor cannot be compiled until the compiler knows the type of the member variable myValue , it is the compiler's responsibility to remember the definition of accessor until it sees myValue 's declaration.
In both C and C++, one can define nested struct types, but the scope is interpreted differently: in C++, a nested struct is defined only within the scope/namespace of the outer struct, whereas in C the inner struct is also defined outside the outer struct.
In computer programming, a declaration is a language construct specifying identifier properties: it declares a word's (identifier's) meaning. [1] Declarations are most commonly used for functions, variables, constants, and classes, but can also be used for other entities such as enumerations and type definitions. [1]
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.
The same is syntactically valid but has undefined behavior in C++, [8] however, where only the last-written member of a union is considered to have any value at all. For another example of type punning, see Stride of an array .
The latter list is sometimes called the "initializer list" or "initialization list" (although the term "initializer list" is formally reserved for initialization of class/struct members in C++; see below). A declaration which creates a data object, instead of merely describing its existence, is commonly called a definition.