[illumos-Developer] Ugh... xdr_{float,double} problems

[Garrett D'Amore]

Any update on this?  I've not had a chance yet to backout your change..
I'm not sure what the right thing to do here is... I'd rather have a
"real" fix.

	- Garrett

On Fri, 2011-01-28 at 12:10 -0600, Jason King wrote:
> Ok, however things will still be broken, my fix just breaks (or more
> precisely, breaks everyone's workarounds) faster.  I can probably have
> a true fix later tonight as well.
> 
> On Fri, Jan 28, 2011 at 10:58 AM, Garrett D'Amore <garrett at nexenta.com> wrote:
> > Ok, I'll backout the changes.  Can you please file a bug?  I probably won't
> > get around to backing this change out until tonight as I'm traveling and on
> > limited battery power.
> >
> >    - Garrett
> >
> > On 01/28/11 08:48 AM, Jason King wrote:
> >>
> >> After lengthy discussions, and even more digging... it looks like
> >> there's a bit of a very-long standing mess with the C xdr API.
> >>
> >> The problem is, the OTW XDR format for 32&  64 bit doubles is
> >> identical on x86, amd64, sparc, and sparcv9.  In theory, the code
> >> should then just merely copy the values out unchanged.
> >> However, that really happened was on little-endian platforms, the byte
> >> values for fp values were being (incorrectly) byteswapped by the
> >> library.  Instead of fixing the library, it appears the existing
> >> software that actually uses fp with xdr workaround the bug on those
> >> platforms.  Of course the recent putback broke the workaround.
> >>
> >> Essentially:
> >>
> >> 1. code is released with broken xdr_{float,double}
> >> 2. code is written w/ workarounds
> >> 3. code is updated, and __amd64 define is (incorrectly) changed to
> >> amd64.  This causes xdr_{float,double} to revert to a slower, platform
> >> independent version that correctly (minus rouding errors) writes the
> >> value into the stream (without swapping).
> >> 4. My fix correctly writes fp values unchanged to XDR stream, but also
> >> breaks any software with workarounds.  The test cases were written to
> >> the RFC&  man pages (since I couldn't really find anything out there
> >> that uses
> >>
> >> Given the pervasiveness of this, we probably need to do something similar
> >> to:
> >>
> >> 1. Revert the behavior to the traditional broken behavior
> >> 2. Update the man pages to document this behavior
> >> 3. Add a #define to the rpc/xdr.h header file (XDR_FLOAT_NO_SWAP ?) to
> >> allow applications to select the correct behavior when defined (and
> >> document this in the manpage).
> >>
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> >>
> >
> >
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