[Boost-users] 答复: Boost-users Digest, Vol 2718, Issue 3

11 May 2011

      typedef boost::shared_ptr<A> APtr;

void* callbk1 (void* o) {
   APtr a = *static_cast<APtr*>(o); // or APtr& a = *static_cast<APtr*>(o)
   a->hello();
}

void* callbk1 (void* o) {
   A* a = static_cast<A*>(o);
   a->hello();
}

boost::shared_ptr<A> sPtr(rawPtr);
if before a->hello(), the *rawPtr is not destroy(sPtr may be out of scope, but at least one boost::shared_ptr<A> holds it). Use:
callbk1(&sPtr);  or 
callbk2(sPtr.get());

If sPtr will out of the scope and no other boost::shared_ptr<A> holds *rawPtr, you should new a boost::shared_ptr<A>:
boost::shared_ptr<A>*p = new boost::shared_ptr<A> (sPtr); // keep A life.
// pass p to callback
callbk3(p); // may be invoke in other thread

void callbk3(void* o)
{
   // delete the p = new APtr(sPtr) when return if we only call callbk3 once.
   boost::scoped_ptr<Aptr> pp(static_cast<APtr*>(o)); 
   APtr& a = *pp; // at least we have this one boost::shared_ptr<A>
   a->hello();
}

Best
Regards!

Qiao Zhi Qiang
...
------------------------------
Message: 6
Date: Tue, 10 May 2011 14:24:26 +0530 (IST)
From: Mupparthy Ravindranath <rv_nath@yahoo.com>
To: "boost-users@lists.boost.org" <boost-users@lists.boost.org>
Subject: Re: [Boost-users] How to cast a boost::shared_ptr to void*
Message-ID: <443447.3562.qm@web94809.mail.in2.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"
Sorry for the spam.? I got the answer, how to do it. Ignore my previous mail.
[quote]
#include <boost/shared_ptr.hpp>
#include <iostream>
using namespace std;
class A {
??? public:
??? void hello () { cout << "Hello, friends...!" << endl; }
};
typedef boost::shared_ptr<A> APtr;
void* callbk (void* o) {
??? APtr a = *static_cast<APtr*>(o);
??? a->hello();
}
int main() {
A* rawPtr = new A;
boost::shared_ptr<A>sPtr(rawPtr);
callbk((void*)&sPtr);
return 0;
}
[/quote]
warm regars,
RV

[Boost-users] 答复: Boost-users Digest, Vol 2718, Issue 3

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