[Swig-user] const reference argument but construct on the stack

[the4thamigo_uk <and...@ba...>]

Hi, 

I have a custom string class X, and functions that have input parameters
passed as const X&.

e.g.

void f(const X& foo);

I want to create a typemap such that a python string is converted to an
instance of X by allocation on the stack e.g.

%typemap(in) const X& { 
	X x( PyString_AsString($input) ); 
	$1 = x
}

However, it seems that swig generates code such that $1 is a pointer to X,
so that in order to get swig to work I must allocate on x on the heap and
provide a freearg typemap to deallocate it after the function call. 

I did try simply getting the address x e.g.

%typemap(in) const X& { 
	X x( PyString_AsString($input) ); 
	$1 = &x
}

.... but this doesnt work because the cxx wrapper code places the typemap
code within curly braces, so this code sets arg1 to be a dangling pointer...
e.g.

  {
    X x( PyString_AsString(obj0) ); 
    arg1 = &x;
  }
  f((X const &)*arg1);


What is the solution to this as I dont want to be forced to always allocate
on the heap for efficiency reasons.

Thanks

Andy
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