Re: problem with "gc" tag method

[Waldemar Celes <celes@...>]

The created object in your "makeobj" function is assigned to global var,
thus not being garbage collected.

> function makeobj (allocator,args)
>       result = call(allocator.new,args)  <<<<<<< SHOULD BE A LOCAL VAR
>

-- waldemar


----------------------------------------------------

> I'm trying to get C++ objects created with tolua garbage
> collected.  Setting the "gc" tag method from within Lua
> seems like it's the right thing to do, and it works if
> I do it "by hand".  But if I try to encapsulate that idea
> into its own function, it fails.  I'm using Lua 3.2.  The
> C++ objects are implemented using Tolua.  The C++ objects
> print something like [alloc empty vec 0x........] when they
> are created, and [destroy vec 0x........] when they are
> deleted.
>
> This seems like a bug to me, but maybe there is something
> I'm missing.
>
> Tom
>
> Here is the Lua code:
>
> ======================================================================
> use_makeobj = nil
>
> print("start")
>
> function delmethod (x)
>     print("delmethod",x)
>     x:delete()
> end
>
> print("delmethod is",delmethod)
>
> function makeobj (allocator,args)
>     result = call(allocator.new,args)
>     settagmethod(tag(result),"gc",delmethod)
>     print("tag",tag(result))
>     print("gc tag method is",gettagmethod(tag(result),"gc"))
>     return result
> end
>
> print("calling makeobj")
>
> if use_makeobj then
>     v = makeobj(Vec,{})
> else
>     v = Vec.new()
>     settagmethod(tag(v),"gc",delmethod)
> end
> print("v is",v)
> print("tag(v) is",tag(v))
>
> print("gc1")
> collectgarbage()
> print("gc tag method is",gettagmethod(tag(result),"gc"))
> v = ""
> print("gc2")
> collectgarbage()
> print("after")
> print("v is",v)
> collectgarbage()
> collectgarbage()
> collectgarbage()
> print("done")
> ======================================================================
>
> Here is the output with use_makeobj=nil:
>
> ======================================================================
> start
> delmethod is    function: 0x806bd30
> calling makeobj
> [alloc empty vec 0x806afd0]
> v is    userdata: 0x806afd0
> tag(v) is       -13
> gc1
> gc tag method is        nil
> gc2
> delmethod       userdata: 0x806afd0
> [destroy vec 0x806afd0]
> after
> v is
> done
> ======================================================================
>
> And here is the output with use_makeobj=1:
>
> ======================================================================
> start
> delmethod is    function: 0x806bd30
> calling makeobj
> [alloc empty vec 0x806afd0]
> tag     -13
> gc tag method is        function: 0x806bd30
> v is    userdata: 0x806afd0
> tag(v) is       -13
> gc1
> gc tag method is        function: 0x806bd30
> gc2
> after
> v is
> done
> ======================================================================