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Asked: 2026-05-11T03:13:04+00:00

Why is it impossible to have a reference to void? The only thing I

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Why is it impossible to have a reference to void? The only thing I found in the C++ Standard is this line, at 8.3.2.1

A declarator that specifies the type ‘reference to cv void’ is ill-formed.

Why is it that way? Why can’t I write a ‘generic’ function that accept a void&?

Just to be clear, I have no useful application in mind where using a reference-to-void could be better than using templates, but I’m just curious about the rationale for forbidding this construct.

To clarify a little, I understand that using a reference-to-void ‘as is’ would be as meaningless as dereferencing a pointer-to-void. However, I could cast it to a reference-to-sometype in order to use it, couldn’t I? In fact, I don’t see why the following snippet can work…

void foo(void *data) {     int *i = reinterpret_cast<int*>(data);     // do something with i }

…while this one cannot:

void foo(void &data) {     int &i = reinterpret_cast<int&>(data);     // do something with i }
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  1. If you did have a reference to void, what would you do with it? It wouldn’t be a number, or a character, or a pointer, or anything like that. Your hypothetical generic function couldn’t perform any operation on it, except taking its address (and not its size).

    ‘void’ has two uses: to disclaim any knowledge of type (as in void *), and to specify nothing as opposed to something (void function return). In neither case is it possible to say anything about a void something except that it may have an address.

    If you can’t think of a way something can be useful, and I can’t, that is at least evidence that something is useless, and that may well be at least part of the rationale here.

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