Re: Question about interpretation of ISO C++ standard

From: rwgk_at_[hidden]
Date: 2001-05-18 12:32:01

Attached is another response from Compaq.
What are the implications for Boost.Python?
Ralf

Date: Fri, 18 May 2001 12:29:16 -0400
From: cxxc_bugs_at_[hidden]
To: rwgk_at_c...
Subject: Re: CPP#5241: Subj:    cxx_bugreport: problem with friend 
functions

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Bjarne Stroustrup's "C++ Programming Language", third
edition, section 11.5.1, explains the behaviour:

"Like a member declaration, a friend declaration does
not introduce a name into an enclosing scope.
...
For large programs and classes, it is nice that
a class doesn't "quietly" add names to its enclosing
scope. 
...
A friend function can be explicitly declared just
like the friend classes, or it can be found
through its argument types as if it was declared
in the non-class scope immediately enclosing its
class.

If follows that a friend function should either
be explicitly declared in an enclosing scope
or take an argument of its class. If not
the friend cannot be called. For example:

// no f() here

void g();  // X's friend

class X {
     friend void f();  // useless
     friend void g();
     friend void f(const X&); // can be found through its argument
}

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