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Re: howto debug libthread_db
Michael Snyder wrote:
On Tue, 2006-09-26 at 16:06 +0200, Carmelo Amoroso wrote:
Hi All,
I'm trying to debug a simple multithread application on a remote target,
and I like to debug the libthread_db itself... is it possible to do it?
is it possible to set some breakpoints and stepping through?
Is there anyone already played with it?
I tried to use symbol-file to gdb client, and I successfully added a
breakpoint, but I cannot reach it after I connected to the target and
issued 'continue'.
Any help will be appreciated
Interesting. I haven't done it (or not much anyway).
The first thing you must bear in mind is that libthread_db is not
part of the target application -- it is part of gdb (or in the
remote debugging context, part of gdbserver). So to debug it,
you must debug gdb, or in your case gdbserver.
Yes. it's what I want to do
It might be easier if you try this out first using a native gdb,
debugging itself.
When you debug gdb with gdb, it is easier if you change the prompt.
I usually do this in the 'parent' gdb, so I can tell it apart from
the 'child' gdb:
(gdb) set prompt (GDB)
(GDB)
Now, in the parent GDB, you should be able to set your
breakpoints in libthread_db, then start the child gdb,
load the multi-threaded program, and begin debugging it.
Does the native gdb use the thread_db as the gdbserver does?
I was thinking to run gdb --args my-gdbserver <application>
ont the target, and connect to the my-gdbserver from the host
just to trigger the thread_db initialization process.
Comments?
When you get ready to try this with gdbserver, you will
have to start one gdbserver and attach to it with another
gdbserver. Then you'll again have two gdbs running on the
host side, which you can again think of as parent and child,
only now the parent is debugging the child's gdbserver, not
the child gdb itself.
Well, just before reading your reply, I tried with this:
target:
gdbserver localhost:999 my-gdbserver localhost:998 <applcation>
host:
xxx-gdb my-gdbserver (connecting to port 999)
xxx-gdb application (connecting to port 998)
Wit the first gdb session I was able to set a breakpoint into thread_db,
but not able to stepping through the code.
Is this approach as well as the gdb native session.
Btw, I'll try again (both the native and the remote technique)
Thanks a lot
Carmelo