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Initialization is distinct from (and preceded by) declaration, although the two can sometimes be conflated in practice. The complement of initialization is finalization, which is primarily used for objects, but not variables. Initialization is done either by statically embedding the value at compile time, or else by assignment at run time.
(However, default initialization to 0 is a right practice for pointers and arrays of pointers, since it makes them invalid before they are actually initialized to their correct value.) In C, variables with static storage duration that are not initialized explicitly are initialized to zero (or null, for pointers).
C++ allows more than one constructor. The other constructors must have different parameters. Additionally constructors which contain parameters which are given default values, must adhere to the restriction that not all parameters are given a default value. This is a situation which only matters if there is a default constructor.
The new syntax, however, allows the default value (42) to be expressed in the implementation rather than the interface — a benefit to maintainers of library code since default values for function parameters are “baked in” to call sites, whereas constructor delegation allows the value to be changed without recompilation of the code using ...
When a class constructor does not explicitly call the constructor of one of its object-valued fields in its initializer list, the default constructor for the field's class is called. In the standard library, certain containers "fill in" values using the default constructor when the value is not given explicitly. E.g.
The placement overloads of operator new and operator delete that employ an additional void * parameter are used for default placement, also known as pointer placement. Their definitions by the Standard C++ library, which it is not permitted for a C++ program to replace or override, are: [7] [8] [9]
The most vexing parse is a counterintuitive form of syntactic ambiguity resolution in the C++ programming language. In certain situations, the C++ grammar cannot distinguish between the creation of an object parameter and specification of a function's type. In those situations, the compiler is required to interpret the line as a function type ...
All variables declared within a block of code are automatic by default. An uninitialized automatic variable has an undefined value until it is assigned a valid value of its type. [1] The storage-class specifier auto can be added to these variable declarations as well, but as they are all automatic by default, this is entirely redundant and ...