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From "Xiao-Feng Li (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-5395) [drlvm] vm.classloading.ClassCastTest hangs
Date Mon, 21 Jan 2008 14:38:36 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-5395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12561022#action_12561022
] 

Xiao-Feng Li commented on HARMONY-5395:
---------------------------------------

Btw, Ilya, since we found Linux64 gcc compiler indeed has various bugs, you probably can dig
out one case of atomic operation by understanding if its generated assembly really has wrong
instructions, if that helps.

For your reference, some known wrong instructions generated by Linux64 gcc are related to
local variable processing. That is, if a local variable is taken its address, gcc probably
will not able to deal with it correctly. For example:

foo(){
  int a = 0;
  tar( &a);
  //a might still be 0 without taking back the value assigned in tar().  

  char b = 'c';
  *(char*)(&a) = b;
  //a might still be 0.
}

If this is the case, some address-taken operations in atomic operation might have wrongly
generated code. 

This is bad to deal with a buggy compiler. It's not really bad to have a buggy compiler, but
it's bad to have such kind of naiive bug in it. Hope this could help your debugging.



> [drlvm] vm.classloading.ClassCastTest hangs
> -------------------------------------------
>
>                 Key: HARMONY-5395
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5395
>             Project: Harmony
>          Issue Type: Bug
>          Components: DRLVM
>         Environment: revision 612006 release mode
> Linux x86_64
>            Reporter: Andrey Yakushev
>         Attachments: atomics.patch
>
>
> [drlvm] vm.classloading.ClassCastTest stably hangs on first iteration

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