Valgrind的抱怨条件跳转或移动依赖于未初始化的值（一个或多个）

Question

我一直在运行的valgrind通过我的应用程序由于其他各种问题，我不断看到有关的警告：

==26447== Conditional jump or move depends on uninitialised value(s) 
==26447== at 0x5C244F: int std::__int_to_char<char, unsigned long>(char*, unsigned long, char const*, std::_Ios_Fmtflags, bool) (in /home/alex/projects/Icarus/trunk/build/icarus) 
==26447== by 0x5C2BB3: std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_int<unsigned long>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, unsigned long) const (in /home/alex/projects/Icarus/trunk/build/icarus) 
==26447== by 0x5C2E1C: std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, unsigned long) const (in /home/alex/projects/Icarus/trunk/build/icarus) 
==26447== by 0x5DB0BD: std::ostream& std::ostream::_M_insert<unsigned long>(unsigned long) (in /home/alex/projects/Icarus/trunk/build/icarus) 
==26447== by 0x55C9B8: ExampleProcessor::Process(std::shared_ptr<Example>) (ExampleProcessor.hpp:49) 
==26447== by 0x55D139: Controller::FIFO(std::shared_ptr<Message>) (Controller.hpp:51) 
==26447== by 0x55D7C2: TCPConnection::respond(std::string) (TCPConnection.hpp:71) 
==26447== by 0x55DC5E: TCPConnection::handle_read(boost::system::error_code const&, unsigned long) (TCPConnection.hpp:144) 
==26447== by 0x595CD8: void boost::_mfi::mf2<void, TCPConnection, boost::system::error_code const&, unsigned long>::call<boost::shared_ptr<TCPConnection>, boost::system::error_code const, unsigned long>(boost::shared_ptr<TCPConnection>&, void const*, boost::system::error_code const&, unsigned long&) const (mem_fn_template.hpp:271) 
==26447== by 0x591412: void boost::_mfi::mf2<void, TCPConnection, boost::system::error_code const&, unsigned long>::operator()<boost::shared_ptr<TCPConnection> >(boost::shared_ptr<TCPConnection>&, boost::system::error_code const&, unsigned long) const (mem_fn_template.hpp:286) 
==26447== by 0x58A46D: void boost::_bi::list3<boost::_bi::value<boost::shared_ptr<TCPConnection> >, boost::arg<1> (*)(), boost::arg<2> (*)()>::operator()<boost::_mfi::mf2<void, TCPConnection, boost::system::error_code const&, unsigned long>, boost::_bi::list2<boost::system::error_code const&, unsigned long const&> >(boost::_bi::type<void>, boost::_mfi::mf2<void, TCPConnection, boost::system::error_code const&, unsigned long>&, boost::_bi::list2<boost::system::error_code const&, unsigned long const&>&, int) (bind.hpp:392) 
==26447== by 0x5812BD: void boost::_bi::bind_t<void, boost::_mfi::mf2<void, TCPConnection, boost::system::error_code const&, unsigned long>, boost::_bi::list3<boost::_bi::value<boost::shared_ptr<TCPConnection> >, boost::arg<1> (*)(), boost::arg<2> (*)()> >::operator()<boost::system::error_code, unsigned long>(boost::system::error_code const&, unsigned long const&) (bind_template.hpp:102) 
==26447== Uninitialised value was created by a stack allocation 
==26447== at 0x553EAA: ConceptGraph::makeHash() (ConceptGraph.hpp:258) 

所以，我读了各地了一下，发现我可以导入MEMCHECK，并要求特定的内存请求：

std::size_t makeHash () 
{ 
    std::size_t tmp; 

    for (auto & concept : _concepts) 
    tmp += concept->Hash(); 

    for (auto & relation : _relations) 
    tmp += relation->Hash(); 

    for (auto & edge : _adjacency_list) 
    tmp += std::hash<std::size_t>()(edge.first->Hash() + edge.second->Hash()); 

    _hash = std::hash<std::size_t>()(tmp); 

    VALGRIND_CHECK_MEM_IS_DEFINED (_hash, sizeof(std::size_t)); 

    return _hash; 
} 

从该孔家当源自于实际问题的行是：

std::stringstream hash; 
hash << graph->Hash(); 

我知道的是初始化，并确定。

这是什么意思？

如果我理解正确，那么它的一个警告字节可能会丢失？

这是一个误报，还是我错过了别的东西？

Answer 1

std::size_t makeHash () 
{ 
    std::size_t tmp; 

    for (auto & concept : _concepts) 
    tmp += concept->Hash(); 

您可以添加到tmp，但其初始值未指定。