gdb and libc debug symbols

[Timo Buhrmester <fstd.lkml%gmail.com@localhost>]

Hi list,

I'm trying to diagnose a mysterious case of occasionally getting stuck in 
read(2).
In order to obtain a meaningful backtrace with gdb, i've rebuilt (actually, 
upgraded from 6.1.2 to 6.1.4) my system from source, with ``MKDEBUG=yes'' and 
``MKDEBUGLIB=yes'' in my mk.conf.  It provided me with the following files:
$ find /usr/libdata/debug -name '*libc[._]*'
 /usr/libdata/debug/usr/lib/i386/libc.so.12.181.debug
 /usr/libdata/debug/usr/lib/libc.so.12.181.debug

Which seems good, so far.

However:
| $ gdb ./myprogram
| [...]
| (gdb) show debug-file-directory 
| The directory where separate debug symbols are searched for is 
"/usr/libdata/debug".
| (gdb) run
| [...]
| Reading symbols from /usr/lib/libc.so.12...Reading symbols from 
/usr/libdata/debug/usr/lib/libc.so.12.181.debug...(no debugging symbols 
found)...done.
| (no debugging symbols found)...done.
| [...]

Apparently there are no debug symbols in 
``/usr/libdata/debug/usr/lib/libc.so.12.181.debug''?  I can't make sense of 
this.  And sure enough:
| (gdb) bt full
| #0  0x00007f7ff7439538 in read () from /usr/lib/libc.so.12
| No symbol table info available.
| [...]
| (gdb) info sharedlibrary 
| From                To                  Syms Read   Shared Object Library
| [...]
| 0x00007f7ff7438930  0x00007f7ff74ee058  Yes (*)     /usr/lib/libc.so.12
| [...]
| (*): Shared library is missing debugging information.

I'm a bit lost here, and I feel there might be something blatantly obvious I'm 
missing.
Any pointers would be greatly appreciated!

Thanks

  Timo