[vorbis] Serious GCC/EGCS 2.91 bug found (bites rc2)

[Monty]

Hi folks,

The folks on RedHat who have been complaining of poor-quality encodes
prompted us to track down the trouble, and it's a compiler bug.  We
have the asm .s files to prove it :-)

The summary: EGCS (gcc) versions through March 1999, including up to
at least gcc/egcs 2.91.66 have a serious floating point optimization
bug that hits Vorbis.  This is a fairly old gcc version, but RedHat
shipped with it until at least RedHat 6.2.  The broken compile will
produce Ogg files, but the audio quality will have from obvious to
severe artifacts.

Also, because we wanted our RPMs to be compatable with redhat 6 and 7,
we built the RPMs using RedHat 6.2.  That means our RPMs are also
broken.  We'll have an updated, correct build on the vorbis.com site
ASAP.

No other builds on the vorbis.com site are affected.  Building from
source is only affected if the compiler used is egcs 2.91 (or older).
gcc --version will report the compiler version.

Amusingly enough, this EGCS bug was fixed approximately two weeks
after it shipped, but the broken version continued to be shipped for
over a year.

Monty

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