[lldb] Fix qEcho message handling (#145072)

Patch fixes the sync-on-timeout logic in lldb and switches to qEcho
based ping, instead of qC. This fixes vRun message case, when there is
no process yet and qC returns an error.

Author: eleviant

lldb/packages/Python/lldbsuite/test/gdbclientutils.py

@@ -92,6 +92,9 @@ class MockGDBServerResponder:
     class RESPONSE_DISCONNECT:
         pass
 
+    class RESPONSE_NONE:
+        pass
+
     def __init__(self):
         self.packetLog = []
 
@@ -181,6 +184,8 @@ def respond(self, packet):
             return self.qQueryGDBServer()
         if packet == "qHostInfo":
             return self.qHostInfo()
+        if packet.startswith("qEcho"):
+            return self.qEcho(int(packet.split(":")[1]))
         if packet == "qGetWorkingDir":
             return self.qGetWorkingDir()
         if packet == "qOffsets":
@@ -237,6 +242,9 @@ def qProcessInfo(self):
     def qHostInfo(self):
         return "ptrsize:8;endian:little;"
 
+    def qEcho(self):
+        return "E04"
+
     def qQueryGDBServer(self):
         return "E04"
 
@@ -655,6 +663,8 @@ def _handlePacket(self, packet):
         if not isinstance(response, list):
             response = [response]
         for part in response:
+            if part is MockGDBServerResponder.RESPONSE_NONE:
+                continue
             if part is MockGDBServerResponder.RESPONSE_DISCONNECT:
                 raise self.TerminateConnectionException()
             self._sendPacket(part)

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

@@ -354,8 +354,9 @@ GDBRemoteCommunication::WaitForPacketNoLock(StringExtractorGDBRemote &packet,
             disconnected = true;
             Disconnect();
           }
+        } else {
+          timed_out = true;
         }
-        timed_out = true;
         break;
       case eConnectionStatusSuccess:
         // printf ("status = success but error = %s\n",

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

@@ -406,7 +406,7 @@ void GDBRemoteCommunicationClient::GetRemoteQSupported() {
         m_supports_qXfer_memory_map_read = eLazyBoolYes;
       else if (x == "qXfer:siginfo:read+")
         m_supports_qXfer_siginfo_read = eLazyBoolYes;
-      else if (x == "qEcho")
+      else if (x == "qEcho+")
         m_supports_qEcho = eLazyBoolYes;
       else if (x == "QPassSignals+")
         m_supports_QPassSignals = eLazyBoolYes;

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

@@ -356,6 +356,78 @@ def A(self, packet):
             ["vRun;%s;61726731;61726732;61726733" % (exe_hex,)]
         )
 
+    def test_launch_lengthy_vRun(self):
+        class MyResponder(MockGDBServerResponder):
+            def __init__(self, *args, **kwargs):
+                self.started = False
+                return super().__init__(*args, **kwargs)
+
+            def qC(self):
+                if self.started:
+                    return "QCp10.10"
+                else:
+                    return "E42"
+
+            def qfThreadInfo(self):
+                if self.started:
+                    return "mp10.10"
+                else:
+                    return "E42"
+
+            def qsThreadInfo(self):
+                return "l"
+
+            def qEcho(self, num):
+                resp = "qEcho:" + str(num)
+                if num >= 2:
+                    # We have launched our program
+                    self.started = True
+                    return [resp, "T13"]
+
+                return resp
+
+            def qSupported(self, client_supported):
+                return "PacketSize=3fff;QStartNoAckMode+;qEcho+;"
+
+            def qHostInfo(self):
+                return "default_packet_timeout:1;"
+
+            def vRun(self, packet):
+                return [self.RESPONSE_NONE]
+
+            def A(self, packet):
+                return "E28"
+
+        self.server.responder = MyResponder()
+
+        target = self.createTarget("a.yaml")
+        # NB: apparently GDB packets are using "/" on Windows too
+        exe_path = self.getBuildArtifact("a").replace(os.path.sep, "/")
+        exe_hex = binascii.b2a_hex(exe_path.encode()).decode()
+        process = self.connect(target)
+        lldbutil.expect_state_changes(
+            self, self.dbg.GetListener(), process, [lldb.eStateConnected]
+        )
+
+        process = target.Launch(
+            lldb.SBListener(),
+            ["arg1", "arg2", "arg3"],  # argv
+            [],  # envp
+            None,  # stdin_path
+            None,  # stdout_path
+            None,  # stderr_path
+            None,  # working_directory
+            0,  # launch_flags
+            True,  # stop_at_entry
+            lldb.SBError(),
+        )  # error
+        self.assertTrue(process, PROCESS_IS_VALID)
+        self.assertEqual(process.GetProcessID(), 16)
+
+        self.assertPacketLogContains(
+            ["vRun;%s;61726731;61726732;61726733" % (exe_hex,)]
+        )
+
     def test_launch_QEnvironment(self):
         class MyResponder(MockGDBServerResponder):
             def qC(self):