[mythtv-users] GNU GCC/64-bit/and --enable-symbol-visibility (was Re: IMDB lookups cause crash)
Michael T. Dean
mtdean at thirdcontact.com
Fri Dec 15 00:05:02 UTC 2006
On 12/14/2006 03:34 PM, Anduin Withers wrote:
> You can disable DRI, you can also be the very first one to confirm if the
> symbol visibility option in SVN fixes it (requires gcc 4).
Anduin, although this doesn't answer your question, I can provide a bit
of feedback about the --enable-symbol-visibility option.
The option breaks compiles on 64-bit platforms (at least x86-64) running
FSF GCC 4.1.0 due to a bug in GCC (which also affects Mozilla builds).
The bug was fixed in FSF GCC 4.1.1 (and backported to GCC 4.0.4).
Another bug (which causes similar compile failures (in MythTV and
Mozilla), but is a completely distinct bug) was not fixed. So, the
option also breaks compiles on 64-bit (x86-64) platforms running FSF GCC
4.1.1. GCC devs have said the fix for the second bug is too large to be
placed in the FSF 4.0/4.1 branches, so FSF GCC will not be able to
compile Myth with --enable-symbol-visibility until GCC 4.2.
Note, though, that the same does /not/ apply to RH GCC 4.1.1. Red Hat
backported the fix to their GCC 4.1 branch, so RH GCC 4.1.1 should be
able to compile MythTV with --enable-symbol-visibility on 64-bit
(x86-64) platforms. I have no idea what other distros are patching
their GCC's. I'm guessing--due to the lack of comments/questions about
the issue--that most distros are patching their compilers. Then again,
it may just be that users may not have realized the benefits the option
can bring, yet.
I'd be happy to provide more information/compile logs/whatever, but I'm
pretty sure there's nothing you can do about it (other than what Mozilla
is now doing--detecting the bug during configure and disabling symbol
visibility, if present--which is probably not worth the bytes in
configure). The primary reason I'm even mentioning it is so that you
don't waste a lot of time trying to debug issues if anyone (else) ever
tries the extremely-nice symbol visibility enhancements you went to the
trouble of coding for us and reports any bugs.
BTW, my 32-bit machines (which both have NVIDIA cards, though, so can't
be used to answer your question about the ATI drivers) are happily
running MythTV compiled with --enable-symbol-visibility without any issues.
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