[lldb] [gdb-remote] Always send PID when detaching w/ multiprocess

[mgorny]

Summary

Always send PID in the detach packet when multiprocess extensions are
enabled. This is required by qemu's GDB server, as plain 'D' packet
results in an error and the emulated system is not resumed.

[labath]

A test case?

[mgorny]

Add tests.

[labath]

lldb/test/API/functionalities/gdb_remote_client/TestGDBRemoteClient.py

384

Whether this fires depends on how python was run. Better use regular asserts. You could pass in the test case to MyResponder constructor, or stash client_supported in a member variable for later checks, or ...

[mgorny]

lldb/test/API/functionalities/gdb_remote_client/TestGDBRemoteClient.py

384

Sure, makes sense.

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp

if (keep_stopped) {
     if (m_supports_detach_stay_stopped == eLazyBoolNo) {
       error.SetErrorString("Stays stopped not supported by this target.");
       return error;
     } else {
       packet.PutChar('1');
     }
   }
 
-  if (pid != LLDB_INVALID_PROCESS_ID) {
-    if (!m_supports_multiprocess) {
-      error.SetErrorString(
-          "Multiprocess extension not supported by the server.");
-      return error;
-    }
+  if (m_supports_multiprocess) {
+    // Some servers (e.g. qemu) require specifying the PID even if only a single
+    // process is running.
+    if (pid == LLDB_INVALID_PROCESS_ID)
+      pid = GetCurrentProcessID();
     packet.PutChar(';');
     packet.PutHex64(pid);
+  } else if (pid != LLDB_INVALID_PROCESS_ID) {
+    error.SetErrorString("Multiprocess extension not supported by the server.");
+    return error;
   }
 
   StringExtractorGDBRemote response;
   PacketResult packet_result =
       SendPacketAndWaitForResponse(packet.GetString(), response);
   if (packet_result != PacketResult::Success)
     error.SetErrorString("Sending isconnect packet failed.");
   return error;

lldb/test/API/functionalities/gdb_remote_client/TestGDBRemoteClient.py

def test_launch_QEnvironmentHexEncoded_only(self):
         self.assertPacketLogContains([
           "QEnvironmentHexEncoded:504c41494e3d666f6f",
           "QEnvironmentHexEncoded:4e45454453454e433d66726f6224",
           "QEnvironmentHexEncoded:4e45454453454e43323d66722a6f62",
           "QEnvironmentHexEncoded:4e45454453454e43333d66726f7d62",
           "QEnvironmentHexEncoded:4e45454453454e43343d6623726f62",
           "QEnvironmentHexEncoded:455155414c533d666f6f3d626172",
         ])
+
+    def test_detach_no_multiprocess(self):
+        class MyResponder(MockGDBServerResponder):
+            def __init__(self):
+                super().__init__()
+                self.detached = None
+
+            def qfThreadInfo(self):
+                return "10200"
+
+            def D(self, packet):
+                self.detached = packet
+                return "OK"
+
+        self.server.responder = MyResponder()
+        target = self.dbg.CreateTarget('')
+        process = self.connect(target)
+        process.Detach()
+        self.assertEqual(self.server.responder.detached, "D")
+
+    def test_detach_pid(self):
+        class MyResponder(MockGDBServerResponder):
+            def __init__(self, test_case):
+                super().__init__()
+                self.test_case = test_case
+                self.detached = None
+
+            def qSupported(self, client_supported):
+                self.test_case.assertIn("multiprocess+", client_supported)
+                return "multiprocess+;" + super().qSupported(client_supported)
+
+            def qfThreadInfo(self):
+                return "mp400.10200"
+
+            def D(self, packet):
+                self.detached = packet
+                return "OK"
+
+        self.server.responder = MyResponder(self)
+        target = self.dbg.CreateTarget('')
+        process = self.connect(target)
+        process.Detach()
+        self.assertRegex(self.server.responder.detached, r"D;0*400")