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Subject: [Bug libstdc++/54314] [4.8 Regression] undefined references to 'construction vtable for std::ostream-in-std::basic_ostringstream<char, std::char_traits<char>, std::allocator<char> >'
Date: Mon, 28 Jan 2013 15:43:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54314

--- Comment #27 from Jason Merrill <jason at gcc dot gnu.org> 2013-01-28 15:42:57 UTC ---
(In reply to comment #26)
> 1) Just add the check.  We will then miss all devirtualization oppurtunities
>    through the construction vtable.

The front end does devirtualization itself for calls within constructors, so
the impact of this isn't likely to be too bad.

>    what happens on targets not supporting visibility?

I think that setting DECL_VISIBILITY should do the trick even if it isn't
reflected in the assembly output.  I added the DECL_ARTIFICIAL check to
default_assemble_visibility so that this wouldn't cause warnings.

> 3) Perhaps we can use DECL_VALUE_EXPR or somethin similar to keep track of
>    the canonical way to reffer into tthe construction vtable? (i.e. by
> reference
>    to vtable) We can then lower all direct references to the indirect
>    references late, i.e. in expansion?

Hmm, that makes sense.