debugging threads on 64bit GNU/Linux with 32bit debugger?

[Daniel Jacobowitz]

On Wed, Aug 15, 2007 at 12:36:49PM -0700, Joel Brobecker wrote:
> Here is the situation: We're using a gcc/gdb toolset built on a 32bit
> x86-linux machine. We're using this toolset on a 64bit machine running
> a 64bit GNU/Linux machine. The resulting executable is runing in 32bit
> compatibility mode.
> 
> Everything seems to be working fine, except that we're having trouble
> debugging threaded apps. The thread library used is the NPTL, and the
> debugger is reporting to use what seems to be the correct (32bit)
> instance of the libthread_db library (the 32bit version in /lib/tls,
> not the one in /lib64/tls).
> 
> The debugger fails at startup time saying:
> 
>         [Thread debugging using libthread_db enabled]
>         Cannot find new threads: generic error

The answer is that you need a bunch of kernel patches for this to
work.  You may want to try a very current kernel; I don't know when
the patches were applied, but I believe they have been at this point.
It was probably some point between 2.6.17 and 2.6.22.

-- 
Daniel Jacobowitz
CodeSourcery