Is sizeof(void()) a legal expression?

Question

From [5.3.3/1], I found that:

The sizeof operator shall not be applied to an expression that has function or incomplete type

Fro

Answer 1

As already highlighted in the docs here http://en.cppreference.com/w/cpp/language/sizeof

Notes

sizeof() cannot be used with function types, incomplete types, or bit-field glvalues.

Since void() is a function type, so its not a valid type of sizeof()

Note:

void() is a function that takes no arguments and returns nothing

Quoting a Example from Docs:

//<< "size of function: " << sizeof(void()) << '\n'  // error

So Answers to your questions:

1)No it is not a legal Expression.

2)It will show as 1 , but will show a warning

3)same as 1).