http://buildlogs.mongodb.org/build/51824031d2a60f31d2000107/test/5182e052d2a60f407500080c/
Thu May 02 18:42:27.713 [conn13] KERNELBASE.dll
DebugBreak+0x2
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\util\debug_util.cpp(46)
mongo::mongo_breakpoint+0x22
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\util\debug_util.h(65)
mongo::breakpoint+0x25
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\util\assert_util.cpp(121)
mongo::verifyFailed+0x2b0
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\bson\bson-inl.h(183)
mongo::BSONElement::embeddedObject+0x6a
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\commands\mr.cpp(845)
mongo::mr::State::finalReduce+0x622
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\commands\mr.cpp(1266)
mongo::mr::MapReduceCommand::run+0x151b
m31100| Thu May 02 18:42:27.713 [conn124] warning: we think data is
in ram but system says no
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\dbcommands.cpp(2015)
mongo::_execCommand+0xb0
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\dbcommands.cpp(2126)
mongo::Command::execCommand+0xb19
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\dbcommands.cpp(2218)
mongo::_runCommands+0x3f6
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\ops\query.cpp(50)
mongo::runCommands+0x7b
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\ops\query.cpp(955)
mongo::runQuery+0x48c
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\instance.cpp(235)
mongo::receivedQuery+0x2f0
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\instance.cpp(374)
mongo::assembleResponse+0x353
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\db\db.cpp(194)
mongo::MyMessageHandler::process+0x133
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\mongo\util\net\message_server_port.cpp(206)
mongo::PortMessageServer::handleIncomingMsg+0x676
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\third_party\boost\boost\bind\bind.hpp(244)
boost::_bi::list1<boost::_bi::value<mongo::PortMessageServer::HandleIncomingMsgParam
* __ptr64> >::operator()<void * __ptr64,void * __ptr64 (__cdecl*)(void
* __ptr64),boost::_bi::list0>+0x56
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\third_party\boost\boost\bind\bind_template.hpp(21)
boost::_bi::bind_t<void * __ptr64,void * __ptr64 (__cdecl*)(void *
__ptr64),boost::_bi::list1<boost::_bi::value<mongo::PortMessageServer::HandleIncomingMsgParam
* __ptr64> > >::operator()+0x61
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\third_party\boost\boost\thread\detail\thread.hpp(63)
boost::detail::thread_data<boost::_bi::bind_t<void * __ptr64,void *
__ptr64 (__cdecl*)(void *
__ptr64),boost::_bi::list1<boost::_bi::value<mongo::PortMessageServer::HandleIncomingMsgParam
* __ptr64> > > >::run+0x2f
m31100| Thu May 02 18:42:27.713 [conn13] mongod.exe
...\src\third_party\boost\libs\thread\src\win32\thread.cpp(185)
boost::`anonymous namespace'::thread_start_function+0x4c
m31100| Thu May 02 18:42:27.713 [conn13] writing minidump diagnostic
file mongo.dmp
according to mathias, probably this link: https://github.com/mongodb/mongo/blob/master/src/mongo/db/commands/mr.cpp#L845