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https://issues.apache.org/jira/browse/QPID-3193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171945#comment-13171945
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[email protected] commented on QPID-3193:
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This is definitely moving in the right direction. I would request 3 changes.
The changes you made to the use of destructors and finalizers are less correct
than the original code. You are duplicating the work of the IDispose wrapper
created by the compiler. See
"Destructors and Finalizers in Visual C++"
in the Microsoft documentation where it says "Calling the destructor will
suppress (with SuppressFinalize) finalization of the object".
The need for an explicit GC::SuppressFinalize(this) is only needed if there is
an additional mechanism from the IDisposable interface to allow user control of
the resources. As an example, see AmqpConnection::Close() in the Qpid wcf code.
Regarding your choice of "this" for locking:
WRT lock(this), I think it is the best choice. The entire Message class
storage consists of a single pointer into unmanaged space. There is no
finer-grained object on which to lock than 'this'.
I disagree. The provided library is at risk of deadlock due to sloppy user
code or inadvertent user error. You should use something along the lines of:
Object^ wrapperLock; // private, in .h file
wrapperLock = gcnew Object(); // in constructors
See the openCloseLock in the AmqpSession class in the Qpid wcf code for an
example where more locks were needed than available private objects. Or see
the use of thisLock in IssuedTokenCache.cs in the WCF examples from Microsoft.
The Macro:
I agree with Andrew that the side effects of the macro should be clearly
pointed out. One example, not using a macro, is the use of CheckOpen() in the
wcf client's AmqpSession class (and s/CheckOpen/ThrowIfDisposed/ for your
case). This is probably how most .NET programmers would approach it since they
tend not to prefer compactly written code over descriptive code.
However I am sympathetic to the magnitude of intrusion of the change to your
wrapper class which suddenly makes your code appear to be as much about
mutithreading as it is about its real job. Given that the complexities of the
managed/unmanaged boundary dwarf your intended use of the macro, I don't think
any one working with this code would find the macro confusing. If you prefer a
macro, that works for me, provided you address Andrew's concern and switch to
locking on a private reference.
Cliff
- Cliff
On 2011-12-16 21:04:58, Chug Rolke wrote:
bq.
bq. -----------------------------------------------------------
bq. This is an automatically generated e-mail. To reply, visit:
bq. https://reviews.apache.org/r/3239/
bq. -----------------------------------------------------------
bq.
bq. (Updated 2011-12-16 21:04:58)
bq.
bq.
bq. Review request for qpid, Andrew Stitcher, Gordon Sim, Ted Ross, Steve
Huston, and Cliff Jansen.
bq.
bq.
bq. Summary
bq. -------
bq.
bq. QPID-3193 .NET Binding - proper handling of disposed objects.
bq.
bq.
bq. This addresses bug QPID-3193.
bq. https://issues.apache.org/jira/browse/QPID-3193
bq.
bq.
bq. Diffs
bq. -----
bq.
bq. trunk/qpid/cpp/bindings/qpid/dotnet/src/BindingCommon.h PRE-CREATION
bq. trunk/qpid/cpp/bindings/qpid/dotnet/src/Message.h 1215245
bq. trunk/qpid/cpp/bindings/qpid/dotnet/src/Message.cpp 1215245
bq.
trunk/qpid/cpp/bindings/qpid/dotnet/src/msvc10/org.apache.qpid.messaging.vcxproj
1215245
bq.
trunk/qpid/cpp/bindings/qpid/dotnet/src/msvc9/org.apache.qpid.messaging.vcproj
1215245
bq.
bq. Diff: https://reviews.apache.org/r/3239/diff
bq.
bq.
bq. Testing
bq. -------
bq.
bq.
bq. Thanks,
bq.
bq. Chug
bq.
bq.
> .NET Binding for Messaging classes need a test to check that binding is still
> in effect
> ---------------------------------------------------------------------------------------
>
> Key: QPID-3193
> URL: https://issues.apache.org/jira/browse/QPID-3193
> Project: Qpid
> Issue Type: Improvement
> Affects Versions: 0.11
> Reporter: Chuck Rolke
> Assignee: Chuck Rolke
> Attachments: QPID-3694_lock-and-throw-preview.patch
>
>
> The .NET Binding for Messaging could be made more user-friendly with the
> addition of a property that indicates whether or not the underlying binding
> is still available. A C# coder may innocently write:
> (1) Message mA = new Message("a");
> (2) Message mB = mA;
> ...
> (N) mB.Dispose();
> After disposing of message mB then message mA is clobbered. 'Message' is a
> 'ref class' type and messages mA and mB refer to the same object on managed
> heap. When message mB is disposed then the bound C++ Messaging object is
> deleted [1]. Any reference to the bound message part of mA will result in an
> illegal memory reference (to 0) and a process exit. The .NET runtime can't
> catch this fault.
> The obvious answer is not to do that. If the second line of code was 'Message
> mB = new Message(mA)' then mA and mB would have been completely separate and
> disposing of either would have no effect on the other.
> Another answer is to have the binding check for a null binding reference on
> each and every access and then to throw if the underlying binding is gone.
> This is not very appealing from a performance standpoint.
> As a compromise I would like to add a property isBound to each class. Users
> then have a fighting chance to check that the binding is still in effect and
> that function calls on the object shouldn't blow up. This property would be
> useful in Assert statements or in debugging.
> [1] If anyone knows how to have my binding library intercept example code
> line (2) and create reference counts, please let me know.
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