Modifiers

Type modifiers attach to functions and (most of them) to variables. More than one may appear. The basic type is still void, int, float, string, object, mapping, function, mixed, buffer, a class name, or an array of those (int *, mixed **, …).

Visibility

Modifier	Meaning
public	Callable / visible from other objects (the default you should write).
protected	Visible to this program and its inheritors, not via call_other from outside.
private	Visible only in this program file.
nomask	Inheritors may not override this function (or hide this variable).

static is the historic spelling: it means protected + nosave unless the driver was built with sensible-modifier aliases. Prefer protected and nosave in new code.

Persistence

Modifier	Meaning
nosave	Not written by save_object() / not restored. Use on runtime caches, sockets, and UIDs.

Functions

Modifier	Meaning
varargs	Callers may pass fewer arguments than declared; omitted trailing args are 0. The last declared parameter may be a catch-all with ....
async	The function body may await. The call site yields a promise, not the declared return type. See async.

public nomask varargs void log(string msg, mixed extra) {
    if (undefinedp(extra))
        write(msg + "\n");
    else
        write(msg + " " + extra + "\n");
}

private nosave object conn;

async is not a variable modifier

async applies only to functions (including prototypes). It is not legal on variables or in a modifier_change block (async:). Applies such as create / logon must not be async — the driver reads the return value immediately. See async.

ref is not a storage class

ref (and &) mark pass-by-reference parameters, call-site arguments, and foreach loop variables. They are not private-style modifiers. See ref.