#954 Unable to delete derived class through object base pointer

[Jeff Marshall]

As given in the following example we should expect the derived destructor to be called, but is not:

type D extends object
    declare virtual destructor
end type

destructor D
    print "~D()"
end destructor

var x = new D
dim as object ptr y = x

'' delete derived object through base pointer
delete y

For comparison if we have a second derived class, we can destruct the instance through a base pointer:

type VirtualObject extends object
    declare virtual destructor
end type

destructor VirtualObject
    print "~VirtualObject()"
end destructor

type D extends VirtualObject
    declare virtual destructor
end type

destructor D
    print "~D()"
end destructor

var x = new D
dim as VirtualObject ptr y = x

'' delete derived object through base pointer
delete y

/' OUTPUT:
~D()
~VirtualObject()
'/

Reported at https://www.freebasic.net/forum/viewtopic.php?t=31566

This appears to mess with extern "c++" handling and we get a (likely) related issue:

extern "c++"
type foo extends object
    a as integer
    declare virtual destructor
end type
end extern

destructor foo
end destructor

the linker returnsundefined reference to foo::~foo()

[fxm (freebasic.net)]

'OBJECT' has no virtual 'destructor()', and even it has no 'destructor()' at all (only 'constructors').