char（＆test（...））[2]是什么意思？

Question

What is the meaning of the following declaration:

char (& test(...))[2];

I pasted it inside a function body as is and it compiles all right. I don't know what I can do with it but it passes the compilation.

I've encountered something similar in this answer.

Answer 1

It's the declaration of a function taking a variable argument list and returning a reference to an array of 2 char .

Note that if define a function like this the parameters are inaccessible (via standard means) as the <cstdarg> macros require a variable argument list to follow a named parameter.

If you like, you can defined a function with this declaration and return a reference to suitable array. You can call it with any parameters, subject to the restrictions for ... parameters which include the restrictions that passing non-POD class types causes undefined behaviour.

Eg

namespace
{
    char samplearray[2];
}

char (& test(...))[2]
{
    return samplearray;
}

Answer 2

Declare test as a vararg function returning a reference to an array of 2 char s

A useful site for de-mangling such declarations is cdecl: C gibberish <-> English (although it doesn't understand varargs and is C oriented rather than C++).