Can an unnamed parameter of function have a default value?

c++, c++11, default-parameters, function, function-signature

Solution

Yes, it's legal.

There is no standard wording to allow this combination of features specifically; there simply isn't any to disallow it, either.

Default argument syntax applies to function parameters in a parameter-declaration:

`[C++11: 8.3.6/1]:` If an initializer-clause is specified in a parameter-declaration this initializer-clause is used as a default argument. Default arguments will be used in calls where trailing arguments are missing.

...and function parameters in a parameter-declaration may be unnamed:

`[C++11: 8.3.5/11]:` [..] An identifier can optionally be provided as a parameter name. [..]

There is even an example of this usage under 8.3.6/4 (though examples are not normative text, so this cannot be used to prove anything concretely).

Problem

Is the following code legal in C++? ``` void f(void* = 0) {} int main() { f(); } ``` Which page of the C++ standard states that this usage is legal?

Original source