[PATCH] gdb, thread-iter: handle null_ptid

[Markus Metzger <markus.t.metzger@intel.com>]

Fix a regression introduced by

    0618ae41497 gdb: optimize all_matching_threads_iterator

and exposed by

    FAIL: gdb.btrace/enable-new-thread.exp: ... (GDB internal error)

When we learn about a new thread in a new inferior, we add both and notify
GDB about them, but we do not set inferior_ptid.

On the notification, record-btrace tries to enable recording of the new
thread and, while reading the configuration, checks whether inferior_ptid
is replaying.

This causes the new all_matching_threads_iterator to think we want to
iterate over a single thread, while in reality we do not really want to
iterate over any thread.

Handle that case.
---
 gdb/thread-iter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/thread-iter.c b/gdb/thread-iter.c
index e56ccd857b0..a2018fd7c10 100644
--- a/gdb/thread-iter.c
+++ b/gdb/thread-iter.c
@@ -117,7 +117,7 @@ all_matching_threads_iterator::all_matching_threads_iterator
 	  if (m_inf != nullptr)
 	    m_thr = &m_inf->thread_list.front ();
 	}
-      else
+      else if (filter_ptid != null_ptid)
 	{
 	  /* Iterate on a single thread.  */
 	  m_mode = mode::SINGLE_THREAD;
-- 
2.31.1

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