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From: "lhyatt at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug lto/106274] Loss of macro tracking information with -flto
Date: Wed, 13 Jul 2022 17:48:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106274

--- Comment #4 from Lewis Hyatt <lhyatt at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> I'm not sure to what extent this is still required with respect to the
> diagnostic context though - you'd have to try.

Thanks for the explanation, the general nature of it makes sense to me now.
There is one current testcase (g++.dg/20090121-1.C) which demonstrates that
it's not OK to simply skip calling tree_diagnostics_defaults () entirely for
-flto... For that testcase, the -Wuninitialized diagnostic calling back into
the C+ frontend (cp_printer) would ICE after ipa-free-lang-data pass if so.

It seems like it should be doable to address this, maybe frontends could
specify how they want ipa-free-lang-data to adjust their diagnostic context=
, so
it wouldn't have to be all or nothing. I can look into that sometime, perha=
ps
it would help with enabling this pass to run during non-LTO compilation as
well.=