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Are handles garbage collected?
| Are handles garbage collected? [message #4739] |
Fri, 14 July 1995 00:00 |
chase
Messages: 62
Registered: May 1993
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If I lose a handle ID is the dynamic memory allocated to that handle
forever lost?
This would appear to be the case that it is lost since handle IDs are
not builtin data types but are stored in long integers. Hence
references to handles can not be kept track of (unless all long
integer valuesare checked before they are overwritten - a very
unlikely implementation). If I store a handle ID in a single location
and then overwrite that location the ID is lost. As a result the
memory can never be freed with handle_free.
It would seem that handle usage could be a source of memory leaks in
programs.
I like the concept of handles to create heterogeneous arrays/lists.
However, I am reluctant to use them wholesale in code manipulating
large amounts of data. Memory leak problems could be very difficult
to debug. Probably my most difficult and common bugs in C programs
are memory management problems associated with pointers. It would
appear that in IDL it is up to the user to manage handle memory -
reintroducing my greatest difficulty from C into IDL.
It would be best if handles were builtin data types so that their
memory would automatically be managed via garbage collection or
reference counting. In fact, references would only need to be checked
for top level handles.
I suppose the same memory leak problem is true with widgets that are
created but never realized and their IDs are lost. Although this only
happens when there is a bug preventing the execution of the code that
realizes and manages widgets. To prevent memory problems without user
intervention would require making widget IDs builtin data types,
probably the same as handles.
Chris
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The Applied Physics Laboratory
The Johns Hopkins University
Laurel, MD 20723-6099
(301)953-6000 x8529
chris.chase@jhuapl.edu
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