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Re: 64bit: cygstdc++-6.dll


On Mar 24 03:33, Yaakov (Cygwin/X) wrote:
> On 2013-03-23 04:50, Corinna Vinschen wrote:
> >On Mar 22 19:11, marco atzeri wrote:
> >>latest libstdc++6-4.8-20130319-1
> >>
> >>has at least a missing entry point from previous dll
> >>
> >>cmake fails with
> >>"_ZTVN10_cxxabiv117_class_type_infoE could not be located"
> >
> >However, a quick glance into the symbols exported by libstdc++.a
> >shows that the above symbol exists, but with additional leading
> >underscores:
> >
> >   _ZTVN10__cxxabiv117__class_type_infoE
> >           ^           ^
> 
> It's hard to see, but the error message actually does have double
> underscores.

I don't quite understand.  From what Marco pasted above, it doesn't.

> >The x86_64 ABI does not prepends underscores in front of symbols,
> >so there has evidently gone something wrong.  I checked my the Linux
> >cross toolchain and it is also using the symbols with additional
> >leading underscores.  Off the top of my head I don't see where this
> >discrepancy is caused.
> 
> The PE underscore only applies to the very beginning of a symbol,
> not to every component of a C++ symbol name.  Those double
> underscores are straight from libstdc++ code, as they are internal
> symbols.
> 
> In any case, the error is a result of adding one of Dave Korn's patches:
> 
> http://cygwin-ports.git.sourceforge.net/git/gitweb.cgi?p=cygwin-ports/gcc;a=blob;f=4.7-libstdc-dllimport.patch;hb=refs/heads/4.8#l29
> 
> I have omitted that patch in the new 4.8.0-1.  Hopefully Dave can
> explain the purpose and necessity of that patch, since it would seem
> that using (at least that hunk of) it would require rebuilding most
> C++ packages in 64bit/release; if it's really necessary, then we
> will want to do that sooner rather than later.

That I don't quite understand either.  If this is only about missing
exported symbols and not about the name, how are the already built
C++ packages affected?  They could be built, so they didn't use this
symbols, apparently.

I'm slightly confused now...


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat


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