Re: [Boost-users] shared_ptr memory leak in VC2005?

From: Ovanes Markarian (om_boost_at_[hidden])
Date: 2007-10-29 09:26:17

This isssue is well discussed in the shared_ptr docs. And it is also
suggested there to use weak_ptr, instead of shared_ptr. shared_ptr can not
resolve cyclic dependencies:

Please read:
http://www.boost.org/libs/smart_ptr/shared_ptr.htm

...
"Because the implementation uses reference counting, cycles of
*shared_ptr*instances will not be reclaimed. For example, if
*main()* holds a *shared_ptr* to *A*, which directly or indirectly holds a *
shared_ptr* back to *A*, *A*'s use count will be 2. Destruction of the
original *shared_ptr* will leave *A* dangling with a use count of 1. Use
weak_ptr <http://www.boost.org/libs/smart_ptr/weak_ptr.htm> to "break
cycles.""
...

With Kind Regards,
Ovanes Markarian

On 10/29/07, zzp good <baobeileaf_at_[hidden]> wrote:
>
> hi, guys, I found memory leak using the following code:
>
> #include <boost\array.hpp>
> #include <boost\shared_ptr.hpp>
> using namespace boost;
>
> class C
> {
> public:
>     shared_ptr<C> pNext;
> };
>
> void test()
> {
>     shared_ptr<C> c0(new C());
>     shared_ptr<C> c1(new C());
>     c0 -> pNext = c1;
>     c1 -> pNext = c0;
> }
>
> void main()
> {
>     test();
>
>     _CrtDumpMemoryLeaks();
> }
>
> when running with F5, it said:
>
> Detected memory leaks!
> Dumping objects ->
> d:\program files\microsoft visual studio 8\vc\include\crtdbg.h(1147) :
> {126} normal block at 0x003A64B0, 16 bytes long.
>  Data: <  E         hd: > C4 17 45 00 01 00 00 00 01 00 00 00 68 64 3A 00
> d:\program files\microsoft visual studio 8\vc\include\crtdbg.h(1147) :
> {125} normal block at 0x003A6468, 8 bytes long.
>  Data: < c:  d: > D0 63 3A 00 18 64 3A 00
> d:\program files\microsoft visual studio 8\vc\include\crtdbg.h(1147) :
> {124} normal block at 0x003A6418, 16 bytes long.
>  Data: <  E          c: > C4 17 45 00 01 00 00 00 01 00 00 00 D0 63 3A 00
> d:\program files\microsoft visual studio 8\vc\include\crtdbg.h(1147) :
> {123} normal block at 0x003A63D0, 8 bytes long.
>  Data: <hd:  d: > 68 64 3A 00 B0 64 3A 00
> Object dump complete.
>
> Any body have an idea about this? Thanks very much.
>
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