[Swig-devel] [ swig-Bugs-1875074 ] [csharp] getCPtr should use object.ReferenceEquals

[SourceForge.net <no...@so...>]

Bugs item #1875074, was opened at 2008-01-18 17:05
Message generated for change (Comment added) made by koro666
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101645&aid=1875074&group_id=1645

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: csharp
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Koro (koro666)
Assigned to: William Fulton (wsfulton)
Summary: [csharp] getCPtr should use object.ReferenceEquals

Initial Comment:
The internal getCPtr function uses operator== to compare
the "obj" parameters instead of using object.ReferenceEquals. This has bad side effects if the class has defined operator== (with %typemap(cscode)) that calls another wrapped function in the class (leading to an infinite loop)

As an attachment, a patch to correct the problem (which I hope I created correctly).


----------------------------------------------------------------------

Comment By: Koro (koro666)
Date: 2009-04-19 10:33

Message:
This was from a while ago, at a job I don't even work at anymore :)

Basically I was trying to work around the fact that the csharp module
doesn't wrap C++ operators. So what I did basically was:

1- %rename all of C++ operators in a class with "proper names" (aka
operator== becomes OperatorEqual) so they could be wrapped as regular
functions.
2- Make said functions private in the C# wrapper class.
3- Use %typemap(cscode) to add code to the C# class implementing a proper
operator== that just calls the private function from 1.

Now obviously, OperatorEqual will call getCPtr, which uses == (aka the C#
class's operator==) to check if obj is null. Since I defined it to call
OperatorEqual, which internaly calls getCPtr... bam, infinite recursion.

I don't think it matters much if Object.ReferenceEquals or
(object)obj==null is used to compare if obj is null, as long as it makes
sure to not call the operator== function if it's defined.

----------------------------------------------------------------------

Comment By: William Fulton (wsfulton)
Date: 2009-04-10 19:28

Message:
Using (object)obj == null could also be used instead. In the MSDN docs
http://msdn.microsoft.com/en-us/library/ms173147(VS.80).aspx on overloading
operator==, it suggests the operator== should be using the cast to object.
Perhaps your operator== isn't following the guidelines? Can you please
provide a testcase showing the problem? Thanks.

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=101645&aid=1875074&group_id=1645