Re: pthread_t ids of threads not showed by "thread info"

[Pedro Alves <pedro at codesourcery dot com>]

On Thursday 22 April 2010 16:44:04, Stefano Sabatini wrote:
> > (gdb) info threads
> > * 9 Thread 25919  0x0040cc7d in PSafeObject::LockReadOnly (this=0xb6d3d1d8)
> >     at ../common/safecoll.cxx:144
> >   8 Thread 25920  0x00885402 in __kernel_vsyscall ()

For core files, older GDBs printed:

      8 process 25920  0x00885402 in __kernel_vsyscall ()

instead.  I'm thinking that the change so s/process/Thread/ in
corelow.c:core_pid_to_str to default to print "Thread" wasn't
that great.  The idea was that "process" isn't good either,
since now GDB supports multi-process, and so it's also confusing.

What would people say to a change like this (pseudo-patch):

 static char *
 core_pid_to_str (struct target_ops *ops, ptid_t ptid)
 {
   static char buf[64];

   if (core_gdbarch
       && gdbarch_core_pid_to_str_p (core_gdbarch))
     {
       char *ret = gdbarch_core_pid_to_str (core_gdbarch, ptid);
       if (ret != NULL)
 	return ret;
     }

   if (ptid_get_lwp (ptid) == 0)
     xsnprintf (buf, sizeof buf, "<main task>");
   else
-     xsnprintf (buf, sizeof buf, "Thread %ld", ptid_get_lwp (ptid));
+     xsnprintf (buf, sizeof buf, "LWP %ld", ptid_get_lwp (ptid));

   return buf;
 }

That is, default to print "LWP" instead.  

For core files, older GDBs printed:

      8 LWP 25920  0x00885402 in __kernel_vsyscall ()

I think that'll make more sense for the majority of
hosts/targets that support core files.  At least more
than "Thread ".

The gdbarch callback was added specifically for Solaris,
so that we'd print "LWP " there:

char *
sol2_core_pid_to_str (struct gdbarch *gdbarch, ptid_t ptid)
{
  static char buf[80];

  xsnprintf (buf, sizeof buf, "LWP %ld", ptid_get_lwp (ptid));
  return buf;
}

we could get rid of it, and instead register callbacks to
whatever targets/archs want "Thread " instead.  Note that there
are a few targets that do layer a thread_stratum layer
on top of corelow.c (at least OpenBSD, and Solaris'
sol-thread.c), and those are already overriding
core_pid_to_str to print whatever else they want instead,
using the regular target_ops inheritance mechanisms.  I'm
thinking that Cygwin core files would be a case where you
don't have a thread_stratum, but still want "Thread".  These
kinds of targets sounds like the minority, so flipping the
default seems to make sense, and be less confusing to
users.

Opinions?

-- 
Pedro Alves