Detect cycles in WeakHashMaps

[eclipsewebmaster]

| --- | --- | | Bugzilla Link | 296826 | | Status | ASSIGNED | | Importance | P3 enhancement | | Reported | Dec 03, 2009 11:22 EDT | | Modified | Feb 25, 2020 16:12 EDT | | Version | 1.1 | | Depends on | 297052 | | See also | Gerrit change https://git.eclipse.org/r/158295, Git commit e6465836, Gerrit change https://git.eclipse.org/r/158301, Git commit a78a213e, Gerrit change https://git.eclipse.org/r/158350, Git commit d8e9667e | | Reporter | Andrew Johnson |

Description

WeakHashMaps have entries with a key held by the reference of a WeakReference and a value. If the key is no longer accessible and is only weakly reachable then it can be cleared and then the hash map entry can be cleared.

A user error is to have a path from the value to the key. The key is then strongly referenced via the WeakReference value field and won't be cleared when otherwise inaccessible.

We should detect this problem.