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

["Yaakov (Cygwin/X)" <yselkowitz at users dot sourceforge dot net>]

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.

> 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.


Yaakov

P.S. I'll be offline until Thursday.