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Re: [PATCH] Define TARGET_LIBC_PROVIDES_SSP for targets using glibc,use TLS access sequences on i386/x86_64/ppc/ppc64


Richard Henderson wrote:
> Only after it's released,

So what?  The new gcc will likewise not be available right away and
therefore there is no need to have support available right now.


> It wouldn't if you exported the __stack_guard_value variable all of
> the time, rather than 100% reliance on the tls magic.  In that case
> glibc becomes forward compatible with libgcc's implementation.

No, because there are all kinds of problems with symbol lookup and the
optimizations thereof, copy relocations etc.  Yes, it could be
implemented very slowly and compatible in this way but it's not
acceptable since in the long run the problem goes away.  But then it's
too late for an ABI change to rectify the ABI.

As said above, there is no need to support the new interfaces right the
second the changes hit the gcc cvs archive.  If anything, developers are
even more reluctent to update to a new major gcc version than they are
updating glibc (there are still tons of programs which still don't
compile with gcc 4.0).  So the chances are good that by the time that
gcc version is available a reasonably new glibc is in use as well.  And
the packagers can ensure this by adding appropriate dependencies if
necessary.

-- 
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â

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