[Bug remote/30054] New: qC response is ignored with S packet.

[Bug remote/30054] New: qC response is ignored with S packet.

[abidh at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30054

            Bug ID: 30054
           Summary: qC response is ignored with S packet.
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: remote
          Assignee: unassigned at sourceware dot org
          Reporter: abidh at sourceware dot org
  Target Milestone: ---

We have noticed a change in behaviour since
24ed6739b699f329c2c45aedee5f8c7d2f54e493. Please see the log below. Targets
send a S00 packet in the start. GDB gets the thread information using qC packet
and target supplies that information in the response. Later GDB ignores it and
picks the first thread anyway.

I investigated it a bit and it seems that thread information that was obtained
in start_remote_1 gets overwritten by switch_to_inferior_no_thread. Later when
S00 packet is processed, it obviously does not have thread information and GDB
ends up calling select_thread_for_ambiguous_stop_reply.

[remote] Sending packet: $qTStatus#49
  [remote] Packet received: 
  [remote] packet_ok: Packet qTStatus (trace-status) is NOT supported
  [remote] Sending packet: $?#3f
  [remote] Packet received: S00
  [remote] Sending packet: $qfThreadInfo#bb
  [remote] Packet received: mp2890.1
  [remote] Sending packet: $qsThreadInfo#c8
  [remote] Packet received: mp2890.2
  [remote] Sending packet: $qsThreadInfo#c8
  [remote] Packet received: mp2890.3
  [remote] Sending packet: $qsThreadInfo#c8
  [remote] Packet received: mp2890.4
  [remote] Sending packet: $qsThreadInfo#c8
  [remote] Packet received: l
  [remote] Sending packet: $qAttached:2890#9c
  [remote] Packet received: 
  [remote] packet_ok: Packet qAttached (query-attached) is NOT supported
  [remote] Sending packet: $Hc-1#09
  [remote] Packet received: OK
  [remote] Sending packet: $qC#b4
  [remote] Packet received: QCp2890.3
  [remote] Sending packet: $qOffsets#4b
  [remote] Packet received: 
  [remote] wait: enter
    [remote] select_thread_for_ambiguous_stop_reply: enter
      [remote] select_thread_for_ambiguous_stop_reply: process_wide_stop = 0
      [remote] select_thread_for_ambiguous_stop_reply: first resumed thread is
Thread 10384.1
      [remote] select_thread_for_ambiguous_stop_reply: is this guess ambiguous?
= 1
warning: multi-threaded target stopped without sending a thread-id, using first
non-exited thread
    [remote] select_thread_for_ambiguous_stop_reply: exit
  [remote] wait: exit

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[Bug remote/30054] qC response is ignored with S packet.

[abidh at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30054

Hafiz Abid Qadeer <abidh at sourceware dot org> changed:

           What    |Removed                     |Added
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                 CC|                            |aburgess at redhat dot com

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