[jira] [Commented] (ZOOKEEPER-1643) Windows: fetch_and_add not 64bit-compatible, may not be correct

["Benjamin Reed (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13575594#comment-13575594 ] 

Benjamin Reed commented on ZOOKEEPER-1643:
------------------------------------------

we should also use __sync_fetch_and_add in the non windows case :)
                
> Windows: fetch_and_add not 64bit-compatible, may not be correct
> ---------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1643
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1643
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: c client
>    Affects Versions: 3.3.3
>         Environment: Windows 7
> Microsoft Visual Studio 2005
>            Reporter: Erik Anderson
>
> Note: While I am using a really old version of ZK, I did do enough "SVN Blame" operations to realize that this code hasn't changed.
> I am currently attempting to compile the C client under MSVC 2005 arch=x64.  There are three things I can see with fetch_and_add() inside of /src/c/src/mt_adapter.c
> (1) MSVC 2005 64bit will not compile inline _asm sections.  I'm moderately sure this code is x86-specific so I'm unsure whether it should attempt to either.
> (2) The Windows intrinsic InterlockedExchangeAdd [http://msdn.microsoft.com/en-us/library/windows/desktop/ms683597(v=vs.85).aspx] appears to do the same thing this code is attempting to do
> (3) I'm really rusty on my assembly, but why are we doing two separate XADD operations here, and is the code as-written anything approaching atomicity?
> If you want an official patch I likely can do an SVN checkout and submit a patch the replaces the entire #else on lines 495-505 with a "return InterlockedExchangeAdd(operand, incr);"
> Usually when I'm scratching my head this badly there's something I'm missing though.  As far as I can tell there has been no prior discussion on this code.

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