On Tuesday, November 16, 2010 10:59:38 am you wrote:
> On Tue, Nov 16, 2010 at 6:46 PM, Dave Steffen <dave.stef...@numerica.us>
wrote:
> > Hi Folks
> >
> > I've been tracking down some almost-certainly-false-positives.
> > Consider the following code:
> >
> >
> > #include <iostream>
> > #include <boost/shared_ptr.hpp>
> > #include <boost/make_shared.hpp>
> >
> >
> > using namespace std;
> > using boost::make_shared;
> >
> > struct StateSpace {
> > public:
> >
> > StateSpace(int spaceType) {
> > if (spaceType == 4)
> > cout << "Some Output" << endl;
> > }
> > };
> >
> > class State {
> > public:
> >
> >
> > State() : m_rep(make_shared<StateSpace>(0) ) {} // #1
> > // State() : m_rep(new StateSpace(0) ) {} // #2
> >
> >
> > boost::shared_ptr<StateSpace> m_rep;
> > };
> >
> >
> > int main() {
> > State state;
> > }
> >
> >
> > Valgrind 3.6 reports this:
> >
> > ==8198== Memcheck, a memory error detector
> > ==8198== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
> > ==8198== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for
> > copyright info
> > ==8198== Command: testState
> > ==8198==
> > ==8198== Conditional jump or move depends on uninitialised value(s)
> > ==8198== at 0x401659: StateSpace::StateSpace(int) (testState.cpp:14)
> > ==8198== by 0x401796: boost::shared_ptr<StateSpace>
> > boost::make_shared<StateSpace, int, >(int&&, ) (make_shared.hpp:150)
> > ==8198== by 0x4016BD: State::State() (testState.cpp:22)
> > ==8198== by 0x401317: main (testState.cpp:29)
> > ==8198==
> > ==8198==
> > ==8198== HEAP SUMMARY:
> > ==8198== in use at exit: 464 bytes in 5 blocks
> > ==8198== total heap usage: 240 allocs, 236 frees, 45,162 bytes
> > allocated ==8198==
> > ==8198== LEAK SUMMARY:
> > ==8198== definitely lost: 0 bytes in 0 blocks
> > ==8198== indirectly lost: 0 bytes in 0 blocks
> > ==8198== possibly lost: 0 bytes in 0 blocks
> > ==8198== still reachable: 464 bytes in 5 blocks
> > ==8198== suppressed: 0 bytes in 0 blocks
> > ==8198== Reachable blocks (those to which a pointer was found) are not
> > shown. ==8198== To see them, rerun with: --leak-check=full
> > --show-reachable=yes ==8198==
> > ==8198== For counts of detected and suppressed errors, rerun with: -v
> > ==8198== Use --track-origins=yes to see where uninitialised values come
> > from ==8198== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 5
> > from 5)
> >
> >
> > Interestingly, commenting out line 1 and replacing it with line 2
> > produces no errors.
>
> Can you rerun it with: --track-origins=yes ?
>
> Regards
> Gateano Mendola
Yes indeed:
==8416== Memcheck, a memory error detector
==8416== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==8416== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for
copyright info
==8416== Command: testState
==8416==
==8416== Conditional jump or move depends on uninitialised value(s)
==8416== at 0x401659: StateSpace::StateSpace(int) (testState.cpp:14)
==8416== by 0x401796: boost::shared_ptr<StateSpace>
boost::make_shared<StateSpace, int, >(int&&, ) (make_shared.hpp:150)
==8416== by 0x4016BD: State::State() (testState.cpp:22)
==8416== by 0x401317: main (testState.cpp:30)
==8416== Uninitialised value was created by a stack allocation
==8416== at 0x40176A: boost::shared_ptr<StateSpace>
boost::make_shared<StateSpace, int, >(int&&, ) (make_shared.hpp:150)
==8416==
==8416==
==8416== HEAP SUMMARY:
==8416== in use at exit: 464 bytes in 5 blocks
==8416== total heap usage: 238 allocs, 234 frees, 28,778 bytes allocated
==8416==
==8416== LEAK SUMMARY:
==8416== definitely lost: 0 bytes in 0 blocks
==8416== indirectly lost: 0 bytes in 0 blocks
==8416== possibly lost: 0 bytes in 0 blocks
==8416== still reachable: 464 bytes in 5 blocks
==8416== suppressed: 0 bytes in 0 blocks
==8416== Reachable blocks (those to which a pointer was found) are not shown.
==8416== To see them, rerun with: --leak-check=full --show-reachable=yes
==8416==
==8416== For counts of detected and suppressed errors, rerun with: -v
==8416== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 5 from 5)
FWIW, here's the relevent chunk of make_shared.hpp:
template< class T, class Arg1, class... Args > boost::shared_ptr< T >
make_shared( Arg1 && arg1, Args && ... args )
{
boost::shared_ptr< T > pt( static_cast< T* >( 0 ),
boost::detail::sp_ms_deleter< T >() );
boost::detail::sp_ms_deleter< T > * pd = boost::get_deleter<
boost::detail::sp_ms_deleter< T > >( pt );
void * pv = pd->address();
::new( pv ) T( boost::detail::sp_forward<Arg1>( arg1 ),
boost::detail::sp_forward<Args>( args )... );
pd->set_initialized();
T * pt2 = static_cast< T* >( pv );
boost::detail::sp_enable_shared_from_this( &pt, pt2, pt2 );
return boost::shared_ptr< T >( pt, pt2 );
}
Line 150 is the one with the call to ::new
--
Dave Steffen, Ph.D. - Software Engineer
Numerica Corporation <http://www.numerica.us>
4850 Hahns Peak Drive, Suite 200
Loveland, Colorado 80538
main (970) 461-2000 x 227 direct (970) 612-2327
Email: dave.stef...@numerica.us
fax (970) 461-2004
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