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Re: g++-4.5 vs dwarf branch


We spoke on IRC about the details and I think we're clear on the nit
cleanups I wanted to see before you commit/merge all this, but I'll reply
here anyway just for academic trivia.

> - std::pair<_T1, _T2>::second  has incomplete type. This is strange. I
>   haven't been able to reproduce it in a smaller setup. The error looks
>   as follows:
> 
> /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c
> ++/4.5.1/bits/stl_pair.h: In instantiation of  std::pair<const
> elfutils::dwarf_output::debug_info_entry,
> elfutils::dwarf_output::die_info> :
> /home/mark/src/elfutils/libdw/c++/dwarf_output:233:63:   instantiated
> from here
> /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../include/c
> ++/4.5.1/bits/stl_pair.h:77:11: error:  std::pair<_T1, _T2>::second  has
> incomplete type
> /home/mark/src/elfutils/libdw/c++/dwarf_output:146:12: error: forward
> declaration of  struct elfutils::dwarf_output::die_info 
> 
> Which doesn't make sense to me. The code it complains about is an
> invocation of vector<die_info_pair *>.end(). The following "patch" makes
> it go away. But I have no idea why, both code constructs seem to not
> actually use the pair directly:

Yeah, it seems odd since the only things being used are pointers.
If it were a simple case of 'struct opaque *' then it would not matter.
I suspect that the issue here is just that we are implicitly requiring
the template instantiations for std::pair<...>, even though the actual
type std::pair<...> is used only in ways that are ordinarily permissible
for undefined types.


Thanks,
Roland

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