[Buildroot] About remote debugging and library stripping

[Richard Braun <rbraun@sceen.net>]

Hello,

There seems to be some confusion about what has to be done to get remote
debugging actually working with stripped libraries. It seems buildroot
avoids stripping libthread_db entirely, which was introduced by Mike
Frysinger (hello Mike) with c98bc88e3296222a20e59cfb7b9f3ec5aee3be1c.
If you're absolutely certain of this change, then please explain it.
In my experience (and some in-depth search in the sources), libthread_db
and libpthread can both be stripped.

To understand why this is possible, the big picture must get clearer.
First, for those who aren't aware of its existence, libthread_db is part
of the C library. Its purpose is to hide the implementation details of
the threading implementation through a well defined interface that GDB
and gdbserver can use. When gdbserver loads this library, it doesn't
need the debugging or local symbols. The libthread_db library can be
stripped as much as any other library.

This isn't the case for libpthread. As stated in the GDB FAQ [1],
libthread_db actually needs a few local symbols to work with its
libpthread counterpart. The libpthread library should only be stripped
from its debugging symbols (--strip-debug), not its local ones.

To make things even more complicated, gdbserver (and apparently only
gdbserver) has support for Linux threads since before 2008 [2], but
it's limited (you may get weird SIGTRAPs without understanding why).
This is important because currently, libthread_db isn't installed when
using the crosstool-ng backend.

In the hope this will help.

-- 
Richard Braun

[1] http://sourceware.org/gdb/wiki/FAQ
[2] http://sourceware.org/ml/gdb-patches/2007-10/msg00547.html