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Re: bug in throw.c
From: |
Marius Vollmer |
Subject: |
Re: bug in throw.c |
Date: |
03 May 2003 23:47:23 +0200 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 |
Rob Browning <address@hidden> writes:
> address@hidden (David Mosberger-Tang) writes:
>
> > Today I tried to build guile-1.6.3 on ia64 linux but it failed during
> > the build when trying to use guile to generate some documentation.
> > Subsequently, I tried the snapshot from April 4th and it had the same
> > problem. The problem is quite obvious: in throw.c, we find:
> >
> > #if 0/*def __GNUC__*/
> > /* Dirk:FIXME:: This bugfix should be removed some time. */
> > /* GCC 2.95.2 has a bug in its optimizer that makes it generate
> > incorrect code sometimes. This barrier stops it from being too
> > clever. */
> > asm volatile ("" : "=g" (winds));
> > #endif
> >
> > This is clearly bogus: the asm statement claims that it's writing the
> > "winds" variable, which isn't true. On ia64, this has the effect that
> > the "winds" gets corrupted and comes out with value "1". Just
> > disabling the workaround fixes the issue. Perhaps the workaround is
> > legitimate for some platforms, but I suspect it should always be
> > disabled for gcc v3.x or newer.
>
> Interesting. I tracked down the same problem, but thought it was
> because the optimizer was being clever with some other code that was
> using macros to mess with object internals, and inadvertently hiding
> the top-level object from the GC. I fixed it by adding a
>
> scm_remember_upto_here_1 (winds)
>
> just after the abort (), but your explanation makes sense. So if we
> remove the asm, do we know if we still need a scm_remember_upto_here_1
> (winds) to fix the problem Dirk was initially addressing (and would
> that fix it)?
(I did the original fix, not Dirk, so I'm to blame here.)
The original fix is only needed for GCC 2.95.2 and there only for
i386, probably.
I would say it is safe now to just remove the asm bogosity, as has
already been done in the 1.6 branch.
I will port he 1.6 changes to the 1.7 series.
--
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- Re: bug in throw.c,
Marius Vollmer <=