Re: [Swig-user] C# Wrapper PINVOKE System.AccessViolation

[David P. <dpi...@me...>]

These symptoms suggest that the C++ object has been garbage-collected. If you still have a reference to a cppObj, this must mean either that you did not allocate it with new on the C# side (although you say you did), or that you somehow ended up using a copy of the C# wrapper object instead of the original wrapper. Use a debugger to make sure that the swigCMemOwn member of cppObj is true.

Another, less likely possibility is that the cppObj was somehow freed by the C++ code.

From: Griffith, John (ISST, Fort Collins CO) [mailto:joh...@hp...]

Hello,
I hope this is the correct method to ask for help, please forgive me if not and point me in the correct direction.

My situation is as follows:
I have a C++ DLL and a C# Power Shell API that I've written.  We use Swig 2.0.0 to generate a C# wrapper so that I can access the C++ dll.  Everything seems to work great, until I assign my C# object to a variable in Power Shell.  After I run a number of operations using the power shell variable,  I'll suddenly receive System.AccessViolation Exception on any PInvoke call that is issued by the SWIG wrapper.

In my C# code I'm simply doing something like:

Public class MyClass : PSCmdlet
{
    internal cppObj  myObj = new cppObj();

    public MyClass(cppObj _o)
    {
        myObj = _o;
    }

   public string Id
   {
       get{return myObj.getID();}
   }

  [Cmdlet (VerbsCommon.Get, "MyObj")]
   Public class GetMyObj : myCmdlet
  {
      cppvec cpps = getCppObjs();   //I've defined cppvec as a templat in my wrapper .i file, getCppObjs() just gets all of the C++ objects from the C++ dll
      foreach(cppObj o in cpps)
      {
           WriteObject(new MyClass(o));
      }
  }
}


Of course I've instantiated myObj via the constructor.  As I've mentioned all of this seems to work, until I assign the C# object to a power-shell variable.  I suspect that the response may be that this appears to be a power shell issue, but I'm really at a loss as to why I can access said variable a number of times without issue then suddenly get the exception on PINVOKE.

The Power Shell piece looks something like:
$foo = Get-MyObj -Name someName

Then I can access everything from $foo as expected, however after a while, I loose the ability to access anything from the C++ dll.   When I say "after a while" I mean like if I just run:
$foo
 ID
--
Some_id_string

$foo
ID
--
Some_id_string


$foo
ID
--
Some_id_string

$foo
                PUKE!!!

Over and over, after about 5 or 6 times it throws the exception and pukes.

Thanks,
John