[Quickfix-developers] Fixed spurious System.NullReferenceException in .NET Application.toApp()
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[Quickfix-developers] Fixed spurious System.NullReferenceException in .NET Application.toApp()
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From: Vladimir A. <Vla...@FF...> - 2004-10-19 17:03:13
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Oren,
I=20have=20fixed=20a=20nasty=20bug=20in=20.NET=20Application=20class=20in=20=
QuickFIX=201.9.2.
From=20time=20to=20time,=20especially=20under=20high=20system=20load,=20se=
nding=20a=20FIX
message=20throws=20an=20exception=20like=20this=20one:
System.NullReferenceException:=20Object=20reference=20not=20set=20to=20an=20=
instance
of=20an=20object.
=20=20=20at=20FIX.message_order.=3D(message_order*=20,=20message_order*=20=
)
=20=20=20at=20FIX.message_order.__ctor(message_order*=20,=20message_order*=
=20copy)
=20=20=20at
std._Tree<std::_Tmap_traits<int,FIX::FieldBase,FIX::message_order,...>
>.key_comp(_Tree<...>*=20,=20message_order*=20)
=20=20=20at=20FIX.FieldMap.=3D(FieldMap*=20,=20FieldMap*=20)
=20=20=20at=20FIX.Message.=3D(Message*=20,=20Message*=20)
=20=20=20at=20Application.toApp(Application*=20,=20Message*=20message,=20S=
essionID*
sessionID)
=20=20=20at=20FIX.Session.sendToTarget(Message*=20,=20SessionID*=20)
=20=20=20at=20QuickFix.Session.sendToTarget(Message=20message,=20SessionID=
sessionID)
(The=20exception=20was=20thrown=20at=20random=20code=20locations,=20but=20=
always=20"below"
FIX.FieldMap.operator=3D)
As=20I=20have=20found,=20the=20problem=20lies=20in=20mixing=20unmanaged=20=
code=20and
garbage-collected=20data=20structures.=20Method=20toApp()=20creates=20mana=
ged
wrapper=20class=20QuickFix::Message=20for=20unmanaged=20class=20FIX::Messa=
ge,=20calls
managed=20method=20toApp()=20and=20copies=20the=20(modified?)=20message=20=
back=20to
FIX::Message.=20The=20problem=20is=20in=20the=20last=20operation,=20which=20=
will=20fail=20if
the=20.NET=20garbage=20collector=20decides=20to=20move=20QuickFix::Message=
=20in=20memory
while=20the=20unmanaged=20assignment=20operator=20is=20obliviously=20copyi=
ng
toMessage->unmanaged()=20back=20to=20message.=20This=20happens=20quite=20r=
arely=20(once
in=2010000=20messages=20or=20so),=20but=20the=20message=20is=20lost=20and=20=
never=20sent=20to=20the
client=20(sequence=20gap=20does=20not=20occur),=20which=20makes=20the=20pr=
oblem=20very
severe.
=20=20void=20toApp(=20FIX::Message&=20message,=20const=20FIX::SessionID&=20=
sessionID=20)
[simplified]
=20=20{
=20=20=20=20QuickFix::Message=20*=20toMessage=20=3D=20create(=20message=20=
);
=20=20=20=20m_application->toApp(=20toMessage,=20new=20QuickFix::SessionID=
(=20sessionID
)=20);
=20=20=20=20message=20=3D=20toMessage->unmanaged();
=20=20=20=20^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
=20=20}
The=20solution=20is=20quite=20easy:=20(well,=20once=20you=20identify=20the=
=20problem...=20;)
Simply=20'tag'=20all=20pointers=20to=20GC'ed=20classes=20with=20"__pin"=20=
keyword:
=20=20=20=20QuickFix::Message=20__pin=20*=20toMessage=20=3D=20create(=20me=
ssage=20);
The=20toMessage=20object=20stays=20locked=20in=20memory=20in=20the=20metho=
d=20body=20even=20if
GC=20is=20activated.
I=20have=20seen=20the=20problem=20only=20in=20toApp(),=20but=20I=20believe=
=20that=20toAdmin()=20is
affected=20in=20the=20same=20way.=20Since=20'pinning'=20a=20pointer=20for=20=
a=20short=20time
does=20not=20hurt=20performance,=20I=20decided=20to=20'pin'=20all=20QuickF=
ix::Message
pointers=20in=20the=20Application=20class.
It=20is=20quite=20possible=20that=20other=20C#-to-C++=20wrappers=20suffer=20=
from=20the=20same
problem,=20but=20I=20have=20not=20analyzed=20them.
Important=20note:=20I=20was=20unable=20to=20reproduce=20the=20problem=20wh=
ile=20executing=20a
QuickFIX=20application=20in=20Visual=20Studio.NET's=20debugger.=20The=20ap=
plication
must=20be=20executed=20stand-alone=20from=20the=20command=20line,=20becaus=
e=20VS.NET
changes=20the=20way=20the=20garbage=20collector=20works.=20Both=20Debug=20=
and=20Release
builds=20produce=20the=20same=20erroneous=20behaviour.
Here=20is=20the=20diff:
---=20Application.h=092004-05-31=2015:27:42.000000000=20+0200
+++=20Application.h.new=092004-10-19=2017:22:15.011923000=20+0200
@@=20-71,7=20+71,7=20@@
=20
=20=20=20void=20toAdmin(=20FIX::Message&=20message,=20const=20FIX::Session=
ID&=20sessionID
)
=20=20=20{
-=20=20=20=20QuickFix::Message=20*=20toMessage=20=3D=20create(=20message=20=
);
+=20=20=20=20QuickFix::Message=20__pin=20*=20toMessage=20=3D=20create(=20m=
essage=20);
=20=20=20=20=20m_application->toAdmin(=20toMessage,=20new=20QuickFix::Sess=
ionID(
sessionID=20)=20);
=20=20=20=20=20message=20=3D=20toMessage->unmanaged();
=20=20=20}
@@=20-79,7=20+79,7=20@@
=20=20=20void=20toApp(=20FIX::Message&=20message,=20const=20FIX::SessionID=
&=20sessionID=20)
=20=20=20throw(=20FIX::DoNotSend&=20)
=20=20=20{
-=20=20=20=20QuickFix::Message=20*=20toMessage=20=3D=20create(=20message=20=
);
+=20=20=20=20QuickFix::Message=20__pin=20*=20toMessage=20=3D=20create(=20m=
essage=20);
=20=20=20=20=20try
=20=20=20=20=20{
=20=20=20=20=20=20=20m_application->toApp(=20toMessage,=20new=20QuickFix::=
SessionID(
sessionID=20)=20);
@@=20-95,7=20+95,7=20@@
=20=09=20FIX::IncorrectTagValue&,=20
=20=09=20FIX::RejectLogon&=20)
=20=20=20{
-=20=20=20=20QuickFix::Message=20*=20toMessage=20=3D=20create(=20message=20=
);
+=20=20=20=20QuickFix::Message=20__pin=20*=20toMessage=20=3D=20create(=20m=
essage=20);
=20=20=20=20=20try
=20=20=20=20=20{
=20=20=20=20=20=20=20m_application->fromAdmin
@@=20-122,7=20+122,7=20@@
=20=09=20FIX::IncorrectTagValue&,=20
=20=09=20FIX::UnsupportedMessageType&=20)
=20=20=20{
-=20=20=20=20QuickFix::Message=20*=20toMessage=20=3D=20create(=20message=20=
);
+=20=20=20=20QuickFix::Message=20__pin=20*=20toMessage=20=3D=20create(=20m=
essage=20);
=20=20=20=20=20try
=20=20=20=20=20{
=20=20=20=20=20=20=20m_application->fromApp
@@=20-153,7=20+153,7=20@@
=20=20=20=20=20FIX::MsgType=20msgType;
=20=20=20=20=20unmanaged.getHeader().getField(=20beginString=20);
=20=20=20=20=20unmanaged.getHeader().getField(=20msgType=20);
-=20=20=20=20QuickFix::Message*=20message=20
+=20=20=20=20QuickFix::Message=20__pin=20*=20message=20
=20=20=20=20=20=20=20=3D=20m_factory->create
=20=20=20=20=20=20=20(=20beginString.getValue().c_str(),=20msgType.getValu=
e().c_str()=20);
=20=20=20=20=20message->setUnmanaged(=20unmanaged=20);
Please=20put=20this=20patch=20to=20the=20official=20source=20tree=20ASAP.
Cheers,
=20=20Vlad
-------------------------------------------------------------
Ing.=20Vladimir=20Arnost,=20Developer,=20FFastFill=20Europe=20Ltd.
Vaclavske=20namesti=2055,=20Prague,=20Czech=20Republic
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