[jira] Commented: (AMQCPP-41) Byte swap on float and double truncates values

["Timothy Bish (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/activemq/browse/AMQCPP-41?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_37853 ] 

Timothy Bish commented on AMQCPP-41:
------------------------------------

You'll need to commit a new patch that works against the latest trunk.  Changes have been made that address some of this already.

> Byte swap on float and double truncates values
> ----------------------------------------------
>
>                 Key: AMQCPP-41
>                 URL: https://issues.apache.org/activemq/browse/AMQCPP-41
>             Project: ActiveMQ C++ Client
>          Issue Type: Bug
>    Affects Versions: 1.1
>            Reporter: Albert Strasheim
>         Assigned To: Timothy Bish
>            Priority: Critical
>             Fix For: 1.1
>
>         Attachments: doublefloat-truncate.diff
>
>
> activemq::util::Endian::byteSwap truncates float and double values due to the C-style cast it uses.
> Patch for BytesMessageCommandTest is attached that shows the problem. One might consider expanding this test to check that the minimum, maximum, -1, 0, 1 (and -inf and inf where appropriate) and a few other values can successfully be serialised and deserialised for each of the types.
> Also in the patch is our attempt at fixing byteSwap. You'll notice that we do something very strange: we take the argument of byteSwap and make a copy on the heap. The reason for this is that simply doing:
> {noformat}
> const uintxx_t swapped_val = byteSwap( *(uintxx_t*)(&value) );
> {noformat}
> i.e. taking the address of value instead of using the copy on the heap, fails with GCC 4.0.2 and GCC 4.0.3. I'm guessing GCC might be trying to inline the call to byteSwap and then something goes very wrong when taking the address of a variable on the stack. Hopefully someone has a better idea for a workaround.

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