C++ Scoping Rules Summary

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The following rules apply to all names, including typedef names and class names, provided that C++ allows such names in the particular context discussed:

  • The name itself is tested for ambiguity. If no ambiguities are detected within its scope, the access sequence is initiated.
  • If no access control errors occur, the type of the object, function, class, typedef, and so on, is tested.
  • If the name is used outside any function and class, or is prefixed by the unary scope access operator ::, and if the name is not qualified by the binary :: operator or the member selection operators . and ->, then the name must be a global object, function, or enumerator.
  • If the name n appears in any of the forms X::n, x.n (where x is an object of X or a reference to X), or ptr->n (where ptr is a pointer to X), then n is the name of a member of X or the member of a class from which X is derived.
  • Any name that has not been discussed yet and that is used in a static member function must either be declared in the block it occurs in or in an enclosing block, or be a global name. The declaration of a local name n hides declarations of n in enclosing blocks and global declarations of n. Names in different scopes are not overloaded.
  • Any name that has not been discussed yet and that is used in a nonstatic member function of class X must either be declared in the block it occurs in or in an enclosing block, be a member of class X or a base class of X, or be a global name. The declaration of a local name n hides declarations of n in enclosing blocks, members of the function's class, and global declarations of n. The declaration of a member name hides declarations of the same name in base classes.
  • The name of a function argument in a function definition is in the scope of the outermost block of the function. The name of a function argument in a nondefining function declaration has no scope at all. The scope of a default argument is determined by the point of declaration of its argument, but it cannot access local variables or nonstatic class members. Default arguments are evaluated at each point of call.
  • A constructor initializer is evaluated in the scope of the outermost block of its constructor, so it can refer to the constructor's argument names.

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