Re: GDB to debug threaded application

[Rich Felker <dalias@libc.org>]

On Fri, Apr 06, 2018 at 11:00:48PM +0200, Micha Nelissen wrote:
> On 6 Apr 2018, at 19:22, Rich Felker <dalias@libc.org> wrote:
> > 
> >> On Fri, Apr 06, 2018 at 06:33:35PM +0200, Micha Nelissen wrote:
> >> Hi all,
> >> 
> >> I have built a cross-toolchain (x86-64 to arm, gcc 5.4.0) with musl
> >> (1.1.16) using buildroot (2017.02). I let buildroot build a gdb for
> >> the arm platform. It runs, but when I debug my application, gdb
> >> hangs after a thread is started. Can't interrupt it, have to kill
> >> -KILL my application from another ssh session.
> >> 
> >> I noticed that there is a libthread_db.so in the glibc-based
> >> toolchain. Do I need something similar for musl? That
> >> libthread_db.so needs libc.so.6 (glibc) so I guess I can't use it
> >> as-is?
> >> 
> >> Thanks for any pointers!
> > 
> > No, musl does not use libthread_db.so, but presence of a glibc version
> > of this library could break things badly. Make sure it's not being
> > built or present in any location gdb might search. Are you using a
> > remote/cross gdb (with gdbserver on the target) or local gdb?
> 
> A local gdb. In the buildroot environment, no libthread_db is present I think.

Can you reproduce this behavior (the hang) with a trivial test program
that starts a thread, or does it only happen with your real
application?

Rich