Re: address of virtual member function passed as template argument

From:
pascal.zschumme@gmail.com
Newsgroups:
microsoft.public.vc.language
Date:
18 Mar 2007 11:31:50 -0700
Message-ID:
<1174242710.610813.111500@y80g2000hsf.googlegroups.com>
On 16 Mrz., 22:46, "Alex Blekhman" <x...@oohay.moc> wrote:

<pascal.zschu...@gmail.com> wrote:

Hello

My problem is that the following code using some very
specific stuff
fails to compile on MSVC8:
<code>
// main.cpp
//
// the error is:
// main.cpp(8) : fatal error C1001: internal compiler
error.// (File
"msc1.cpp", Line 1392)

#include <iostream>

// just a simple classtemplatewhich "holds" an address
of a member
//function
// i found out that this class doesn't even need to
contain anything
// else than this to produce the error
template<class Class, void(Class::*MemberFunction)()>
class mfaddr_hold
{
};

class Foo
{
public:
       void f1() {}
       virtualvoid f2() {}
};

class Boom
{
public:
       void f1() {}
       virtualvoid f2() {}

       mfaddr_hold<Foo, &Foo::f1> h1; // other class,
normalfunction
-> works
       mfaddr_hold<Foo, &Foo::f2> h2; // other class,
virtual
function-> works
       mfaddr_hold<Boom, &Boom::f1> h3; // same class,
normal
function-> works
       mfaddr_hold<Boom, &Boom::f2> h4; // same class,
virtual
function-> internal compiler error

};

int main(int argc, char* argv[])
{
       return 0;
}

</code>

The Code works with gcc4.
The problem in MSVC8 is that i can't pass the address of a
virtual
member
functionof a class (here Boom) to a member variable in
the same class
astemplateparameter ;)

Do you guys know any solutions to solve this? any
workarounds?


Possible workaround depends on what `mfaddr_hold' actually
does. Using your code I came up with workaround using
`std::mem_fun_t':

#include <functional>

...

class Boom
{
public:
    Boom() :
      h1(&Foo::f1),
      h2(&Foo::f2),
      h3(&Boom::f1),
      h4(&Boom::f2)
    {}

    void f1() {}
   virtualvoid f2() {}

    std::mem_fun_t<void, Foo> h1;
    std::mem_fun_t<void, Foo> h2;
    std::mem_fun_t<void, Boom> h3;
    std::mem_fun_t<void, Boom> h4;

};

int main()
{
    Boom b;
    Foo f;

    b.h1(&f);
    b.h2(&f);

    b.h3(&b);
    b.h4(&b);

    return 0;

}

Everything compiles and works perfectly.

Alex


The problem is that this doesn't fit my needs. But thank you for your
response.
I want to use Boost.Property and therefor it need to pass those
addresses to boost::property::object_property<...>

consider the following example:
<code>
class foo
{
private:
    int value;

public:
    int getValue() const { return value; }
    void setValue(const int& v) { value = v; }

    boost::scalar_property< boost::object_property
        <
        char, foo,
        &foo::getValue,
        &foo::setValue

         Value;
};
</code>

If you make getValue() oder setValue() virtual, it crashes.
Well, i could pass pointers to getValue and setValue to the property
using it's custuctor at RunTime.
But i had to write my own property-lib for that and (more importantly)
it wouldn't fit into my OOP-system that well. (would be better if
every devired class _had_ to use getValue and setValue for their
properties)

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