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From: "iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/44107] gcc emits frame (epilogue) info incompatible with the darwin {8,9}-unwinder,10-compacter
Date: Sun, 11 Dec 2011 20:04:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44107

--- Comment #18 from Iain Sandoe <iains at gcc dot gnu.org> 2011-12-11 20:01:37 UTC ---
(In reply to comment #17)
> Hello,
> 
> Here comes gcc-4.7.20111203 with (not unexpectedly) exactly the same symptoms
> (see Description above). I tried the patches provided in Comments #4 and #5
> with no success:
> 11 out of 13 hunks FAILED -- saving rejects to file gcc/dwarf2out.c.rej
> 1 out of 3 hunks FAILED -- saving rejects to file gcc/config/darwin.c.rej
> 1 out of 1 hunk FAILED -- saving rejects to file gcc/config/darwin10.h.rej

The mechanism in dwarf2out changed between 4.6 and 4.7 - so the code actually
needs changing.

> The two patches have been working successfully for all 4.6.x versions. Can we
> expect an update  of them for GCC 4.7?

I guess... the thing is that this is not really the 'ideal' solution -
 since by holding the unwinder of Darwin at the 4.4 flavor -  the behavior of
Darwin will start to diverge (more than usual) from that of other systems... 

... so...  I've been investigating other ways of resolving the problem (in
amongst all the other things to be done)...

> P.S.
> Am i the only one needing this patch? As far as i am concerned, i can live with
> the above workaround.

no - you are not - the compiler is essentially broken without a working
unwinder ...

However, Darwin10+ are not affected by this (unless you try to use the unwind
compacter) - so the screaming is not so loud as it might otherwise be ;)

...  I am considering a more radical Darwin-9-only solution (that allows us to
keep track of the current unwinder)
 - time is, as always, the killer ...