[Bug debug/68904] DWARF for class ios_base says it's a declaration

[ivan.soleimanipour at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68904

ivan.soleimanipour at oracle dot com changed:

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--- Comment #5 from ivan.soleimanipour at oracle dot com ---
I see now why Andrew was asking the questions he was asking.

What we failed to notice is that the definition of ios_base in t.o
is abbreviated. It contains only nested classes, 'static const' members and
typedefs. There is no member function or data member information.
There is a more complete definition in `libstdc++.so.6.0.18.

So now the questions become:
- How does gcc decide to emit this abbreviated form?
- Why is it then not _fully_ abbreviated? Why bother with the typedefs and
such?

FWIW -fno-eliminate-unused-debug-types seems to make no difference.