Qpid Messaging .NET Binding fails to translate exceptions from C++ to .NET
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Key: QPID-2923
URL: https://issues.apache.org/jira/browse/QPID-2923
Project: Qpid
Issue Type: Bug
Affects Versions: 0.7
Environment: Windows
Reporter: Chuck Rolke
Assignee: Chuck Rolke
Fix For: 0.7
While adding the FailoverUpdate object a problem in the .NET Binding's scheme
of error handling showed up. This issue will document the original problem and
show a proposed coding pattern to make it better.
Two versions of the FailoverUpdates constructor:
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Original Version
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FailoverUpdates::FailoverUpdates(Connection ^ connection) :
failoverupdatesp(new
::qpid::messaging::FailoverUpdates(*(connection->NativeConnection)))
{
}
This looks OK to me from a pure C++ standpoint. The problem comes from the
environment in which this code runs. It is called by a managed C# or other .NET
caller and it calls into the unmanaged C++ Qpid Messaging code. Using this code
when the C++ code throws, the exception goes to a handler that does not
understand what to do with it.
A. If the user has no try-catch in the .NET calling code then a popup box
shows:
---------------------------
Microsoft Visual C++ Runtime Library
---------------------------
Runtime Error!
Program: ...\src\Debug\csharp.map.sender.vshost.exe
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
"in an unusual way"? What does that mean? This is not good.
*****************
Improved Version
*****************
FailoverUpdates::FailoverUpdates(Connection ^ connection)
{
System::Exception ^ newException = nullptr;
try {
failoverupdatesp = new
::qpid::messaging::FailoverUpdates(*(connection->NativeConnection));
}
catch (const ::qpid::types::Exception & error) {
String ^ errmsg = gcnew String(error.what());
newException = gcnew QpidException(errmsg);
}
if (newException != nullptr) {
throw newException;
}
}
The idea is to catch the exception from native C++ and rethrow it as a
System::Exception.
B. Now the user sees:
An unhandled exception of type 'Org.Apache.Qpid.Messaging.QpidException'
occurred in org.apache.qpid.messagingd.dll
Additional information: Connection has not yet been opened
(..\..\cpp\src\qpid\client\Connection.cpp:139)
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I think the beauty of using a member initialization list is overshadowed by the
fact that the original version mishandles exceptions. I intend to replace all
instances of the .NET binding's constructors with the same pattern.
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