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Re: [platform-swt-dev] usage finalize() as last resort of resource management
- From: Peter Centgraf <peter@xxxxxxxxxxxx>
- Date: Tue, 07 Nov 2006 16:37:24 -0500
- Delivered-to: email@example.com
- User-agent: Thunderbird 18.104.22.168 (Windows/20060909)
Danail Nachev wrote:
The discussion which I
try to find is answer to the question: why finalize() isn't used as last
resort for freeing system resources as it is used for FileInputStream
for example? Am I missing something here?
The last comment on the bug refers to the specific issue in this case, which
is explained in the article. Some things that appear to be garbage on the
Java side (because there are no Java references to them) will still be in use
(because there are OS-level references to them). This bad sequence could happen:
1. Java objects initialize some resources.
2. OS sets up references to resources.
3. Java objects go out of scope.
4. Java objects are finalized.
5. OS resources are disposed.
6. Java call delegates to OS.
7. OS tries to use resources.
8. Pain and suffering.
Take the example (from the article) of an X-Windows GC and Font. A GC can
refer to a Font via OS-level structures. From the Java side, the Font appears
to be garbage, but it's actually still in use. If the Font is disposed by a
finalizer, things will blow up in an ugly way. Your JVM dies with a
Segmentation Fault or somesuch platform-specific nonsense.