Re: %newobject and typemap(out)

Might a "newfree" typemap get you what you want?  I would think so from the std::string example here:

https://www.swig.org/Doc4.0/Typemaps.html#Typemaps_nn34


________________________________
From: Langer, Stephen A. (Fed) via Swig-user <[email protected]>
Sent: Thursday, July 7, 2022 3:14 PM
To: [email protected] <[email protected]>
Subject: [EXTERNAL] Re: [Swig-user] %newobject and typemap(out)

I understand why what I expected to happen doesn’t happen, so I'll rephrase the question:  Is there a way to write a typemap(out) so that it either deletes its source or doesn't, depending on a flag in the swig file that indicates whether or not the object was newly allocated before being returned?

To be specific, I'm trying to do something like this:

%typemap(out) MyClass * {
  $result = some_operations_on($1);
  if(newly_allocated)  // <<-- how???
    delete $1;
}

so that I can do this:

MyClass *getOldObject();
%newobject getNewObject;
MyClass *getNewObject();

or something along those lines.

I know that I can write two typemaps, one for MyClass and one for NewMyClass, put the delete statement only in the NewMyClass typemap, and typedef NewMyClass to MyClass.  Is there a better way?

Thanks,

 -- Steve



-----Original Message-----
From: "Langer, Stephen A. (Fed) via Swig-user" <[email protected]>
Reply-To: "Langer, Stephen A. (Fed)" <[email protected]>
Date: Thursday, July 7, 2022 at 10:20 AM
To: "[email protected]" <[email protected]>
Subject: [Swig-user] %newobject and typemap(out)

    Hi --

    Is it possible for a typemap to know whether or not it's being invoked in conjunction with %newobject?

    If %newobject is used on a function where the return value has a typemap(newfree) but no typemap(out), the wrapper will correctly delete the return value.  But if there's a typemap(out), newfree doesn't seem to be used.  How can a typemap(out) know whether or not it should delete the return value?

    Thanks.
     -- Steve



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