How Does the C Scope Resolution Operator (::) Work Without a Specified Scope?

Global Scope Resolution Without a Scope

In C , the scope resolution operator (::) plays a crucial role in resolving scope and accessing identifiers within the program. However, what happens when the scope resolution operator is used without an explicit scope?

Purpose of :: without a Scope

The scope resolution operator (::) without a scope serves a specific purpose in C . It explicitly specifies the global scope, allowing access to global entities from any point within the program. This mechanism is particularly useful when a function or variable with the same name exists within the current scope and the global version needs to be accessed explicitly.

Syntax and Usage

To access global scope without using an explicit scope identifier, the following syntax is used:

::identifier;

Where identifier can be a function, variable, or class member that exists in the global scope.

An Example

Consider the following example:

void bar();    // Global function

class foo {
    void some_func() { ::bar(); }    // Accessing the global bar()
    void bar();                      // Class member function
};

In this example, both a bar function exist in the global scope and as a member function of the foo class. To invoke the global bar function from within the some_func member function, the :: scope resolution operator is employed to explicitly access the global scope.

By using :: without a scope, programmers can disambiguate identifiers with the same name and ensure that the correct version is accessed from within a specific scope.

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