This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: GNAT vs DW2/ZCX EH.
> Ah, thanks, I'll have to research this change, I don't know about it yet.
Hidden in http://gcc.gnu.org/ml/gcc-cvs/2007-12/msg00267.html
> I'm not sure if I'll find time to investigate reverting it on the branch:
> my priorities are focussed around maintaining the Cygwin distro compiler
> and improving the Cygwin backend on trunk, so I'd prefer to make it work on
> 4.3 rather than revert it, involving local patches that won't be suitable
> for the branch but will be suitable for contributing to trunk for 4.5.
The compiler was working before the change so just reverting it should make it
work again. The change was totally accidental.
> (I've actually got it working beautifully now, tests still running but an
> order of magnitude better than anything I've seen before on Cygwin.
> There's a bunch of other stuff I patched to get it going that I didn't
> mention in this thread, in initialize.c and sysdep.c).
Right, that's why the change should be reverted on the 4.3 branch. On the
other hand, if you can get the ZCX support to work on the mainline before
4.4.0 is released, we could try there.
> Great, thanks, that's good to have confirmed. Incidentally, if I
> understand rightly what's going on here, have you guys managed to make a
> compiler that's runtime-switchable between SjLj and DW2 EH? That would be
> suuuuch a nice feature to have in the core GCC!
The GNAT SJLJ mechanism is not the standard GCC SJLJ mechanism, it's a custom
one. Yes, it's runtime-switchable but this SJLJ mechanism is inferior to the
GCC SJLJ mechanism (and to the ZCX one).
> Right. So I suspect that the critical bits were setting EH_MECHANISM,
> changing ZCX_By_Default, and the ADA_CFLAGS -> ALL_ADA_CFLAGS patching, and
> that adding the -fexceptions flag was superfluous - but harmless, no? I'd
> prefer not to respin this whole release YA time if I don't have to!
Superfluous changes are never harmless in a compiler. :-)
> Thanks for your advice Eric, you've been a great help
You're welcome. Thanks for trying to fiddle with GNAT on Windows. :-)
--
Eric Botcazou