Sowmy Srinivasan wrote:

> How can I embed a fn ptr in auto_ptr and make the indirect fn call
> transparently
> eg.
> auto_ptr<DWORD(*)(int)> pFn = GetFuncPtr();
> DWORD res = pFn(1);
>
> I guess the above statement will not compile unless auto_ptr has
> overloaded operator(). But how can I templatize the
> operator().(Remember
> the number of arguments the func takes is decided by the template
> parameter)


I don't quite understand the problem here. An auto_ptr owns dynamically
allocated objects and automatically deletes them when going out of scope. A
function is not an object, is never created dynamically and can't be
deleted --- s why would you want to store a pointer to a function in an
auto_ptr?

    Regards,
        Brane
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Branko Cibej wrote:

> I don't quite understand the problem here. An auto_ptr owns dynamically
> allocated objects and automatically deletes them when going out of scope. A
> function is not an object, is never created dynamically and can't be
> deleted --- s why would you want to store a pointer to a function in an
> auto_ptr?

I think he might be trying to use auto_ptr to refer to a temporarily
created array of bytes that contains a thunk, such as is often used for
callbacks in 16-bit Windows. But that would require that auto_ptr refer
to a struct containing a function pointer (and perhaps forwarding
operator() to the function), instead of a bare function pointer.

--

Ciao,
Paul

(Please remove the extra "crud" from the return address,
which has been altered to foil junk mail senders.)
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How can I embed a fn ptr in auto_ptr and make the indirect fn call
transparently
eg.
auto_ptr<DWORD(*)(int)> pFn = GetFuncPtr();
DWORD res = pFn(1);

I guess the above statement will not compile unless auto_ptr has
overloaded operator(). But how can I templatize the operator().(Remember
the number of arguments the func takes is decided by the template
parameter)
Any kind of help would be greatly appreciated.

Thanks
sowmy
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Sowmy Srinivasan <KSx_Sowmy@ccm.jf.intel.com> wrote:
: How can I embed a fn ptr in auto_ptr and make the indirect fn call
: transparently
: eg.
: auto_ptr<DWORD(*)(int)> pFn = GetFuncPtr();
: DWORD res = pFn(1);

auto_ptr<> won't work. Not only auto_ptr<> doen't have operator(),
but I doubt you want to delete the pointee :-).
Use pointer_to_unary_function<> (20.3.7) instead.

Oleg.
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Oleg Zabluda wrote:
>
> Sowmy Srinivasan <KSx_Sowmy@ccm.jf.intel.com> wrote:
> : How can I embed a fn ptr in auto_ptr and make the indirect fn call
> : transparently
> : eg.
> : auto_ptr<DWORD(*)(int)> pFn = GetFuncPtr();
> : DWORD res = pFn(1);
>
> auto_ptr<> won't work. Not only auto_ptr<> doen't have operator(),
> but I doubt you want to delete the pointee :-).
> Use pointer_to_unary_function<> (20.3.7) instead.
>
> Oleg.
I am sorry for not making myself clear. Actually I was looking for some
template definition which would be a wrapper to a function pointer (that
takes any type and returns any type) My example is almost correct except
that I used a auto_ptr. Consider a custom pointer-wrapper instead of
auto_ptr. Assume that the custom wrapper does not delete. (See below)

template <class T >
class CApiPtr {
protected:
  T* m_pApi;
public:
  CApiPtr(HMODULE hModule, LPTSTR szApi){
    m_pApi = (T*)GetProcAddress(hModule, szApi);
  }
  operator T*(){ return m_pApi;}
};

Now I can call as below

CApiPtr<DWORD(*)(int)> pFn (hKernel, "GetSystemMetrics");
DWORD res = (*pFn)(1);

But what I was looking for is someway to call as

CApiPtr<DWORD(*)(int)> pFn (hKernel, "GetSystemMetrics");
DWORD res = pFn(1);

THanks
Sowmy
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Oleg Zabluda <zabluda@math.psu.edu> wrote in article
<5n7c3p$219e@r02n01.cac.psu.edu>...
> Sowmy Srinivasan <KSx_Sowmy@ccm.jf.intel.com> wrote:
> : How can I embed a fn ptr in auto_ptr and make the indirect fn call
> : transparently
> : eg.
> : auto_ptr<DWORD(*)(int)> pFn = GetFuncPtr();
> : DWORD res = pFn(1);

You can't.  auto_ptr isn't designed for this.  auto_ptr is *not* a functor
(that is, it does not define an operator()).

Also, how is auto_ptr supposed to call delete (as it does in its dtor) on
such a function pointer?


Best regards,
Matt Arnold
Boston, USA :: http://python.ics.uci.edu/~marnold/
C++/MIDI/Win32/95 developer :: e/DM/7R7/RF/C&E/A-Box

Remove "don't.spam." prefix to obtain my valid email address.
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