Re: Nested is a friend (or not)?

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
comp.lang.c++
Date:
Thu, 03 Sep 2009 12:22:55 +0200
Message-ID:
<h7o5e1$oqs$1@news.eternal-september.org>
* werasm:

Hi All,

I have this minimal bit of code that I found compiles under Comeau and
EDG++, but not under mingw and VC++8.

class Xc;
class Xx
{
  friend class Xc;
  static void doIt();
};

class Xc{ struct Impl; };
struct Xc::Impl
{
  Impl(){ Xx::doIt(); }
};

Should granting friendship to a class not grant friendship to its
nested classes too? I realise friendship is not inheritable, but
it is really constraining to prohibit nested types (which
effectively is part of that class - stronger relationship than
inheritance).

Is this a bug on the part of VCC and MingW or not?


The rules for nested classes have been revamped in C++0x (or will be).

There was a tread about this recently in [comp.lang.c++.moderated], or perhaps
in [comp.std.c++], but I think it was in the first group -- would be nice if
you posted a link if u find it! :-)

Anyway, as I recall the rules for nested classes have swung back and forth even
with the current standard. It seems it's one of those *dirty* corners of the
language. So, best not rely on friendship being transitive to nested classes.

Cheers & hth.,

- Alf

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