| Leaking objects... [message #29931] |
Wed, 27 March 2002 08:08 |
Randall Skelton
Messages: 169
Registered: October 2000
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Senior Member |
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Hi all,
I gave some IDL object code to someone who has no idea what object
programming is. Despite giving her a quick lesson on object life-cycles,
she did the inevitable and directly overwrote an object, creating dangling
pointers. A simplified example is:
The correct way:
IDL> a = obj_new('test', findgen(20))
% Compiled module: TEST__DEFINE.
IDL> obj_destroy, a
IDL> help, /heap ; see Mom, no leaks!
Heap Variables:
# Pointer: 0
# Object : 0
The incorrect way:
IDL> a = obj_new('test', findgen(20))
IDL> ; Dang, did I write findgen(20) there? I meant findgen(30) ...
IDL> a = obj_new('test', findgen(30))
IDL> obj_destroy, a
IDL> help, /heap ; oops
Heap Variables:
# Pointer: 1
# Object : 1
<ObjHeapVar51> STRUCT = -> TEST Array[1]
<PtrHeapVar52> FLOAT = Array[20]
At this point, a variable named 'A' perpetually exists, and is immune to
obj_destroy.
DL> obj_destroy, a
IDL> help
% At $MAIN$
A OBJREF = <ObjHeapVar57>
Compiled Procedures:
$MAIN$ TEST::CLEANUP TEST__DEFINE
Compiled Functions:
TEST::INIT
My question is, how do I prevent this from happening in my code? This
behavior seems a little fragile to me. Ideally, I would like obj_new to
either block the creation of a new object or cleanup pre-existing objects.
What I don't want to do is try and educate the user again... sorry mom.
Thanks in advance,
Randall
-- start: test__define.pro --
pro test::cleanup
ptr_free, self.data
end
function test::init, data
if n_params() ne 1 then begin
message, 'Expecting 1 parameter', /info
return, 0
endif
self.data = ptr_new(data)
return, 1
end
pro test__define
j = { test, data: ptr_new() }
end
-- end: test__define.pro --
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