[jira] [Commented] (BCEL-195) addition of hashCode() to generic/Instruction.java breaks Targeters

["Mark Roberts (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BCEL-195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14695556#comment-14695556 ] 

Mark Roberts commented on BCEL-195:
-----------------------------------

Well, about 6 months later and we still haven't run into any problems with Select.  So I'll answer my own question and say we should just go ahead with the change as proposed.  Thanks.

> addition of hashCode() to generic/Instruction.java breaks Targeters
> -------------------------------------------------------------------
>
>                 Key: BCEL-195
>                 URL: https://issues.apache.org/jira/browse/BCEL-195
>             Project: Commons BCEL
>          Issue Type: Bug
>          Components: Main
>    Affects Versions: 6.0
>            Reporter: Mark Roberts
>         Attachments: b195.diff
>
>
> [Revision 1532198|http://svn.apache.org/r1532198] added a {{hashCode()}} function to the Instruction class.  Unfortunately, this breaks the Instruction targeting mechanism. I understand the goal of trying to reuse instructions - an 'iadd' is the same as any other 'iadd'.  However,  one 'goto 50' is not the same as another 'goto 50' due to the way Targeters are implemented.  If branch instructions are reused, then only one entry gets put on the Targeter list.  So when some api is used to modify the instruction list and location 50 becomes location 52 ONLY ONE of the branches gets updated. A very bad thing.  So unless you modify the hash to special case branch instructions (and there might be other instructions needing special treatment as well) its broken.  We fixed it by simply commenting the hash out to make things like they used to be and all works great.



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