[hjl@lucon.org: Re: Does gdb 5.2 work with statically linked thread application under Linux?]

Daniel Jacobowitz
2002-03-13T17:50:34Z

Does anyone have a comment on this patch? It fixes thread_db for
statically linked binaries (which I broke), and I think it's
legitimate.

----- Forwarded message from "H . J . Lu" <hjl@lucon.org> -----

Date: Thu, 7 Mar 2002 15:08:04 -0800
From: "H . J . Lu" <hjl@lucon.org>
Subject: Re: Does gdb 5.2 work with statically linked thread application under Linux?
To: GDB <gdb@sources.redhat.com>

On Thu, Mar 07, 2002 at 05:02:07PM -0500, Daniel Jacobowitz wrote:
> On Thu, Mar 07, 2002 at 01:39:28PM -0800, H . J . Lu wrote:
> > On Thu, Mar 07, 2002 at 02:48:41AM -0500, Daniel Jacobowitz wrote:
> > > On Wed, Mar 06, 2002 at 11:30:50PM -0800, H . J . Lu wrote:
> > > > Does gdb 5.2 work with statically linked thread application under
> > > > Linux? It doesn't work for me at all. It doesn't know any thread.
> > > > I have a patch which works for gdb 5.1. Now it doesn't work for 5.2
> > > > anymore.
> > >
> > > My fault, I think.
> > >
> > > The problem is that in a dynamically linked binary
> > > thread_db_new_objfile will be called for every library is loaded. At
> > > this point current_target is "child", so target_has_execution is true.
> > > But with a static binary, the first time the function is called objfile
> > > is NULL, and the second time current_target is "exec" (which has
> > > target_has_execution set false).
> > >
> > > Perhaps target_has_execution was not the right check after all, if
> > > "exec" has it set false (which makes fairly little sense to me...) or
> > > perhaps we need to call the hook again later. Michael, any idea?
> > >
> >
> > What is the problem if "|| !target_has_execution" is removed? I removed
> > it. Gdb now works on statically linked thread application as well as
> > core file. Did I miss soemthing?
>
> Try running 'info threads' on the corefile of a multithreaded
> application. Recent Linux kernels will allow them to dump core.
>
> I've also got a patch to put multiple threads into the corefile.
> There's a sample corefile at:
> http://crack.them.org/~drow/mtc2.tar.gz
>
>
> Without !target_has_execution, we try to use lin-lwp on the coredump.
> That works very badly.
>

This patch works for me.

H.J.
----
2002-03-07 H.J. Lu (hjl@gnu.org)

* target.h (target_corefile_hook): New prototype.

* target.c (target_corefile_hook): New.

* corelow.c (core_open): Call target_corefile_hook if needed.

* thread-db.c (thread_db_corefile): New.
(thread_db_new_objfile): Don't check target_has_execution.
(_initialize_thread_db): Set target_corefile_hook to
thread_db_corefile.

--- gdb/corelow.c.static Wed Mar 6 22:30:49 2002
+++ gdb/corelow.c Thu Mar 7 15:01:41 2002
@@ -303,6 +303,9 @@ core_open (char *filename, int from_tty)
filename, bfd_errmsg (bfd_get_error ()));
}

+ if (target_corefile_hook)
+ target_corefile_hook ();
+
/* Looks semi-reasonable. Toss the old core file and work on the new. */

discard_cleanups (old_chain); /* Don't free filename any more */
--- gdb/target.c.static Wed Mar 6 22:31:31 2002
+++ gdb/target.c Thu Mar 7 14:54:50 2002
@@ -38,6 +38,8 @@

extern int errno;

+void (*target_corefile_hook) (void);
+
static void target_info (char *, int);

static void cleanup_target (struct target_ops *);
--- gdb/target.h.static Wed Mar 6 22:31:31 2002
+++ gdb/target.h Thu Mar 7 14:54:38 2002
@@ -985,6 +985,8 @@ extern char *normal_pid_to_str (ptid_t p

extern void (*target_new_objfile_hook) (struct objfile *);

+extern void (*target_corefile_hook) (void);
+
#ifndef target_pid_or_tid_to_str
#define target_pid_or_tid_to_str(ID) \
target_pid_to_str (ID)
--- gdb/thread-db.c.static Wed Mar 6 22:31:31 2002
+++ gdb/thread-db.c Thu Mar 7 14:59:09 2002
@@ -479,13 +479,25 @@ disable_thread_signals (void)
}

static void
+thread_db_corefile (void)
+{
+ if (using_thread_db)
+ {
+ /* If the thread_db target is active, deactivate it now. */
+ gdb_assert (proc_handle.pid == 0);
+ unpush_target (&thread_db_ops);
+ using_thread_db = 0;
+ }
+
+ keep_thread_db = 0;
+}
+
+static void
thread_db_new_objfile (struct objfile *objfile)
{
td_err_e err;

- /* Don't attempt to use thread_db on targets which can not run
- (core files). */
- if (objfile == NULL || !target_has_execution)
+ if (objfile == NULL)
{
/* All symbols have been discarded. If the thread_db target is
active, deactivate it now. */
@@ -1040,5 +1052,6 @@ _initialize_thread_db (void)
/* Add ourselves to objfile event chain. */
target_new_objfile_chain = target_new_objfile_hook;
target_new_objfile_hook = thread_db_new_objfile;
+ target_corefile_hook = thread_db_corefile;
}
}

----- End forwarded message -----

--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer