Re: Using "this" in a base initializer list?

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Tue, 8 May 2007 14:39:14 -0400

Message-ID:

<f1qg4i$qal$1@news.datemas.de>

Alf P. Steinbach wrote:

* Victor Bazarov:

James Kanze wrote:

On May 8, 3:25 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:

Angel Tsankov wrote:

Hello! Is the following code illformed or does it yield undefined
behaviour:
class a
{};
class b
{
public:
b(a&){}
};
class c: private a, private b
{
public:
c():b(*this){}
};

Neither. The code is fine.

Are you sure? Throw in some virtual inheritance, and it core
dumps with Sun CC. [..]

Huh? Throw in division by zero or dereferencing a null pointer
and it may release nasal demons. What's it got to do with the
code at hand?

James is referring to the conversion from c* to a*, which ?3.8/5 says
is Undefined Behavior.

Yes, but where did you find that conversion? There is reference
binding (8.5.3/5), but no pointer conversion.

But the interpretation that yields that
conclusion also means that this,

  struct S
  {
      void foo() {}
      S() { this->foo(); }
  };

is undefined behavior, so that the common technique of using an
init-function called from multiple constructors, would be formally
Undefined Behavior. Which really means that part of the standard is
fishy Fishy FISHY, and should not be taken verbatim: some constructive
interpretation required, and I think it's impossible to say whether
the code above is formally OK (or not), only that it's in-practice OK.

<shrug> The reference (or pointer) is not being converted/used in the
code at all, why all the fuss?

V
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