[PATCH 2/2] gdb, remote: Skip sending of 'vCont' package if remote target is empty

[Stephan Rohr <stephan.rohr@intel.com>]

From: "Rohr, Stephan" <stephan.rohr@intel.com>

If the remote target has no threads that need to be stopped, we can
skip sending the 'vCont' package in 'remote_stop_ns'.
---
 gdb/remote.c                                   |  4 ++++
 .../interrupt-empty-remote-target.exp          | 18 +++++++++++++++++-
 gdb/thread-iter.h                              |  3 +++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index 194c4cbd9bb..8be552b4533 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -7884,6 +7884,10 @@ remote_target::remote_stop_ns (ptid_t ptid)
 	  }
       }
 
+  /* Skip 'vCont' package if there are no threads to be stopped.  */
+  if (all_non_exited_threads (this, ptid).empty ())
+    return;
+
   if (!rs->supports_vCont.t)
     error (_("Remote server does not support stopping threads"));
 
diff --git a/gdb/testsuite/gdb.server/interrupt-empty-remote-target.exp b/gdb/testsuite/gdb.server/interrupt-empty-remote-target.exp
index 34437a17d90..c26b535be16 100644
--- a/gdb/testsuite/gdb.server/interrupt-empty-remote-target.exp
+++ b/gdb/testsuite/gdb.server/interrupt-empty-remote-target.exp
@@ -14,7 +14,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 # Tests that GDB does not assert if interrupting an empty remote target
-# in non-stop mode.
+# in non-stop mode.  Also tests that no 'vCont' package is sent for empty
+# remote targets.
 
 load_lib gdbserver-support.exp
 
@@ -38,3 +39,18 @@ gdb_test_no_output "set non-stop on"
 
 gdb_test "interrupt" \
     "Cannot execute this command without a live selected thread."
+
+gdb_test_no_output "set debug remote on"
+
+# Test that we do not see a 'vCont' package if we interrupt an empty
+# remote target.
+gdb_test_multiple "interrupt -a" "no vCont is sent" {
+    -re -wrap "vCont.*" {
+	fail $gdb_test_name
+    }
+    -re -wrap "" {
+	pass $gdb_test_name
+    }
+}
+
+gdb_test_no_output "set debug remote off"
diff --git a/gdb/thread-iter.h b/gdb/thread-iter.h
index c649560c0e1..cc2b04e7e99 100644
--- a/gdb/thread-iter.h
+++ b/gdb/thread-iter.h
@@ -248,6 +248,9 @@ class all_non_exited_threads_range
   all_non_exited_threads_iterator end () const
   { return all_non_exited_threads_iterator (); }
 
+  bool empty ()
+  { return begin () == end (); }
+
 private:
   process_stratum_target *m_filter_target;
   ptid_t m_filter_ptid;
-- 
2.43.0

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