RE: [Swig-user] Will SWIG C# support multiple exceptions to be thrown?

[Tamas S. <sze...@gm...>]

I was talking about passing multiple exceptions as one (nested) =
exception
that corresponds to the current implementation. In my case the unmanaged
code may generate multiple errors stored in a global error stack within =
a
single function call, and I would like to forward all of the errors to =
the
C# code. With the current imlementation i can pass only one error per =
call.
But with minor modifications of csharphead.swg multiple exceptions could =
be
passed like (based on swig-1.3.28):

...
static void SetPendingIOException(string message) {
SWIGPendingException.Set(new
System.IO.IOException(message,
SWIGPendingException.pendingException));
...



public class SWIGPendingException {
    [ThreadStatic]
    internal static Exception pendingException =3D null;
    private static int numExceptionsPending =3D 0;
...

   public static void Set(Exception e) {
     pendingException =3D e;
     lock(typeof($imclassname)) {
     numExceptionsPending++;
   }
...
}


Tamas


-----Original Message-----
From: William S Fulton [mailto:ws...@fu...]=20
Sent: Tuesday, February 28, 2006 11:11 PM
To: Tamas Szekeres
Cc: swi...@li...
Subject: Re: [Swig-user] Will SWIG C# support multiple exceptions to be
thrown?

Tamas Szekeres wrote:
> Hi,
>=20
> =20
>=20
> The current implementation of the C# binding passes exceptions as=20
> callbacks through a global variable. When the nat=EFve code generates =
two=20
> or more exceptions within a call a new ApplicationException will be=20
> generated.
>=20
> =20
>=20
> In practice it would be desirable to create nested exception instead.=20
> The previous exception could be the inner of the current. To achieve=20
> this at least csharphead.swq should be modified. I could not find a =
way=20
> to redefine the swig exception mechanism without recreating it =
starting=20
>  from scratch.
>=20
> =20
>=20
> Any suggestions will be appreciated
>=20

It should not be possible to throw more than one exception per thread.=20
If you are, please post a small example showing how you do this. The=20
exceptions are stored using a thread local variable not a global=20
variable. The design was made so that more than one exception could=20
occur concurrently when more than one thread was involved, so it is=20
thread safe. There is even a testcase to check this, see the=20
csharp_exceptions.i testcase and the runtime test=20
csharp_exceptions_runme.cs.

William

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