In C++ programming, the scope resolution operator (::) is used to qualify names with a namespace or class scope. Why does the C++ language forbid you from overloading the scope resolution operator (::) in your own classes or libraries?

Introduction / Context:
C++ allows developers to overload many operators so that user defined types can behave like built in types in expressions. However, certain operators, including the scope resolution operator (::), cannot be overloaded. Understanding why some operators are non overloadable is important for both exams and real world design, because it clarifies which parts of the language are controlled strictly by the compiler.

Given Data / Assumptions:

• The question refers specifically to the C++ scope resolution operator (::).
• You already know that C++ supports operator overloading for many operators such as +, -, [], and ().
• You want to know why :: is an exception and cannot be overloaded.
• The context is standard, conforming C++ as defined by the language specification.

Concept / Approach:
The scope resolution operator is used by the compiler to resolve names to a particular namespace, class, or global scope. This decision happens entirely during compilation, before any objects exist at runtime. Because operator overloading is implemented through functions that are called at compile time but executed at runtime, it only makes sense for operators that act on values or objects. Operators that control fundamental aspects of the language syntax, such as ::, ., .*, and ?:, are reserved by the language and cannot be redefined or overloaded by user code.

Step-by-Step Solution:
1. Recall the role of the scope resolution operator: it qualifies identifiers with a specific scope (for example, std::vector or MyClass::member). 2. Observe that this resolution is part of the compiler front end, which decides which symbol a particular name refers to before code generation. 3. Note that operator overloading in C++ is implemented by defining functions with special names that the compiler calls when it sees the corresponding operator being used with user defined types. 4. Realize that for :: there is no user defined type operand and no meaningful runtime behavior to customize; the operator exists purely to guide the compiler in name lookup. 5. The C++ standard therefore declares :: as one of several non overloadable operators, so any attempt to overload it is a violation of the language rules.

Verification / Alternative check:
You can verify this by checking a list of non overloadable operators in C++ references. In addition to ::, the . (member access), .*, ?: (conditional), sizeof, typeid, and a few others cannot be overloaded. Any attempt to declare an operator:: function will result in a compiler error. This is consistent across mainstream compilers because it is mandated by the standard, not by specific implementations.

Why Other Options Are Wrong:
Option b is incorrect because the Standard Template Library does not overload ::; operator overloading is not how namespace or member qualification works. Option c is wrong because :: is a core part of C++ syntax and does not exist in C in the same form; the explanation is backwards. Option d is nonsensical because :: does not return a value at runtime, so the discussion about returning void is irrelevant; the restriction is about compile time name resolution, not return types.

Common Pitfalls:
A frequent misunderstanding is to think that any operator symbol you see can be overloaded if you just write the right function signature. In reality, the C++ standard draws a clear line between operators that represent value level operations and operators that control language structure or introspection. Another pitfall is to think that non overloadable operators are arbitrary limitations; in fact they are fixed to keep the language parsable and predictable for both humans and compilers.

Final Answer:
You cannot overload the scope resolution operator (::) because it is evaluated entirely by the compiler at compile time for name lookup, is not associated with any runtime object, and the C++ language explicitly forbids overloading it.