Where to put default parameter value in C++?

What's the place for the default parameter value? Just in function definition, or declaration, or both places?

Default parameter values must appear on the declaration, since that is the only thing that the caller sees.

EDIT: As others point out, you can have the argument on the definition, but I would advise writing all code as if that wasn't true.

Stack Overflow Q#4989483, score: 365