Re: [Boost-users] Valgrind false positive in make_shared

Subject: Re: [Boost-users] Valgrind false positive in make_shared
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2010-11-16 14:04:26

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On Tuesday 16 November 2010, Dave Steffen wrote:
> ==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)

> Any ideas about why
> Valgrind doesn't like the call to make_shared?  

It looks like it might be a bug in make_shared's perfect forwarding when 
compiling in c++0x mode.  When I compile your example I get a warning:

$ g++ -Wall -g -std=c++0x -I ~/svn/boost_trunk/  make_shared_valgrind.cpp
/svn/boost_trunk/boost/smart_ptr/make_shared.hpp: In function ‘T&& 
boost::detail::sp_forward(T&) [with T = int]’:
/svn/boost_trunk/boost/smart_ptr/make_shared.hpp:150:   instantiated 
from ‘boost::shared_ptr<X> boost::make_shared(Arg1&&, Args&& ...) [with T = 
StateSpace, Arg1 = int, Args = ]’
make_shared_valgrind.cpp:21:   instantiated from here
/svn/boost_trunk/boost/smart_ptr/make_shared.hpp:93: warning: returning 
reference to temporary

> Any ideas about how to 
> silence this warning (other than adding it to Valgrind's suppressions
> file)?

Not forwarding a literal constant works:

class State {
public:

    State() : m_rep(make_shared<StateSpace>(spaceType) ) {}

    static const int spaceType;
    boost::shared_ptr<StateSpace> m_rep;
};
const int State::spaceType = 0;
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