[lldb] Add a gdb_remote_client test for connecting to pty

[mgorny]

Summary

Add a minimal mock server utilizing a pty, and add a client test
connecting to that server.

[mgorny]

@labath, this is the part where I ask for help ;-).

An exception happened when receiving the response from the gdb server. Closing the client...
Traceback (most recent call last):
  File "/home/mgorny/git/llvm-project/lldb/test/API/functionalities/gdb_remote_client/gdbclientutils.py", line 405, in _run
    data = seven.bitcast_to_string(self._client.recv(4096))
  File "/home/mgorny/git/llvm-project/lldb/test/API/functionalities/gdb_remote_client/gdbclientutils.py", line 538, in recv
    return self.read(size)
OSError: [Errno 5] Input/output error
PASS: LLDB (/home/mgorny/git/llvm-project/build/bin/clang-x86_64) :: test_process_connect_sync_dwarf (TestPty.TestPty)

I think it's getting in the 'controlling terminal' magic and getting EIO when lldb finishes or sth like that. Any suggestion how to avoid this exception?

[labath]

In D110878#3034748, @mgorny wrote:

@labath, this is the part where I ask for help ;-).

An exception happened when receiving the response from the gdb server. Closing the client...
Traceback (most recent call last):
  File "/home/mgorny/git/llvm-project/lldb/test/API/functionalities/gdb_remote_client/gdbclientutils.py", line 405, in _run
    data = seven.bitcast_to_string(self._client.recv(4096))
  File "/home/mgorny/git/llvm-project/lldb/test/API/functionalities/gdb_remote_client/gdbclientutils.py", line 538, in recv
    return self.read(size)
OSError: [Errno 5] Input/output error
PASS: LLDB (/home/mgorny/git/llvm-project/build/bin/clang-x86_64) :: test_process_connect_sync_dwarf (TestPty.TestPty)

I think it's getting in the 'controlling terminal' magic and getting EIO when lldb finishes or sth like that. Any suggestion how to avoid this exception?

Catch it and turn it into EOF? (btw, I've found this link to be pretty good at explaining the behavior across different OSs.)

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

530–535

I think it would be cleaner if we had like a single new interface, which describes what to we expect of the connection, and then a socket- and pty-based implementation of that interface.

560–564

I'm wondering if we should have an overload of SBTarget::ConnectRemote that accepts a file descriptor (or SBFile, SBCommunication, ...).

This would make the socket case easier as well, and it seems like it could be generally useful.

[mgorny]

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

560–564

I'm not saying 'no' but I think we'd still want to explicitly test process connect command somewhere.

[mgorny]

Replaced the class hacks with an abstraction over socket & connection sockets.

[labath]

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

22

I think this can be applied at class level

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

409

do you actually need to keep the slave open here?

[mgorny]

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

409

Yes, it seems this way. If I close it early, the test hangs.

[mgorny]

Make it easier to override socket class at GDBRemoteTestBase level. Add async test, mark the whole class skipIfWindows.

[mgorny]

Add get_connect_url() to simplify combining address with proper protocol/prefix.

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

+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+from gdbclientutils import *
+
+
+class TestPty(TestBase):
+    mydir = TestBase.compute_mydir(__file__)
+
+    def setUp(self):
+        super().setUp()
+        self.server = MockPtyGDBServer()
+        self.server.start()
+
+    def tearDown(self):
+        if self.process() is not None:
+            self.process().Kill()
+        self.server.stop()
+        super().tearDown()
+
+    @skipIfWindows
+    def test_process_connect_sync(self):
+        """Test the gdb-remote command in synchronous mode"""
+        try:
+            self.dbg.SetAsync(False)
+            self.expect("platform select remote-gdb-server",
+                        substrs=['Platform: remote-gdb-server', 'Connected: no'])
+            self.expect("process connect file://" +
+                        self.server.get_connect_address(),
+                        substrs=['Process', 'stopped'])
+        finally:
+            self.dbg.GetSelectedPlatform().DisconnectRemote()

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

+import ctypes
 import errno
+import io
 import os
 import os.path
+import pty
 import threading
 import socket
+import tty
 import lldb
 import binascii
 import traceback
 from lldbsuite.support import seven
 from lldbsuite.test.lldbtest import *
 from lldbsuite.test import lldbtest_config
 
 
class MockGDBServer:
     _thread = None
     _receivedData = None
     _receivedDataOffset = None
     _shouldSendAck = True
 
     def __init__(self):
         self.responder = MockGDBServerResponder()
 
-    def start(self):
+    def _bind_and_listen(self):
         family, type, proto, _, addr = socket.getaddrinfo("localhost", 0,
                 proto=socket.IPPROTO_TCP)[0]
-        self._socket = socket.socket(family, type, proto)
-
+        sock = socket.socket(family, type, proto)
 
-        self._socket.bind(addr)
-        self._socket.listen(1)
+        sock.bind(addr)
+        sock.listen(1)
+        return sock
 
+    def start(self):
+        self._socket = self._bind_and_listen()
         # Start a thread that waits for a client connection.
         self._thread = threading.Thread(target=self._run)
         self._thread.start()
 
-    def stop(self):
+    def _close(self):
         self._socket.close()
+
+    def stop(self):
+        self._close()
         self._thread.join()
         self._thread = None
 
     def get_connect_address(self):
         return "[{}]:{}".format(*self._socket.getsockname())
 
     def _run(self):
         # For testing purposes, we only need to worry about one client
def _run(self):
         self._receivedDataOffset = 0
         data = None
         while True:
             try:
                 data = seven.bitcast_to_string(self._client.recv(4096))
                 if data is None or len(data) == 0:
                     break
                 self._receive(data)
             except Exception as e:
                 print("An exception happened when receiving the response from the gdb server. Closing the client...")
                 traceback.print_exc()
                 self._client.close()
                 break
 
     def _receive(self, data):
         """
         Collects data, parses and responds to as many packets as exist.
def _handlePacket(self, packet):
             self._client.sendall(seven.bitcast_to_bytes(framed))
 
     PACKET_ACK = object()
     PACKET_INTERRUPT = object()
 
     class InvalidPacketException(Exception):
         pass
 
+
+class PtySocket(io.FileIO):
+    """Pseudo-pocket wrapping a pty."""
+
+    def __init__(self, fd):
+        tty.setraw(fd)
+        super().__init__(fd, 'r+')
+
+    def accept(self):
+        return self, ''
+
+    def close(self):
+        # the socket is reused, so don't close it yet
+        pass
+
+    def recv(self, size):
+        return self.read(size)
+
+    def sendall(self, data):
+        return self.write(data)
+
+    def settimeout(self, timeout):
+        pass
+
+
+class MockPtyGDBServer(MockGDBServer):
+    """
+    A variation of MockGDBServer that uses a pty instead of TCP.
+    """
+
+    def _bind_and_listen(self):
+        self._master, self._slave = pty.openpty()
+        return PtySocket(self._master)
+
+    def _close(self):
+        os.close(self._slave)
+        os.close(self._master)
+
+    def get_connect_address(self):
+        libc = ctypes.CDLL(None)
+        libc.ptsname.argtypes = (ctypes.c_int,)
+        libc.ptsname.restype = ctypes.c_char_p
+        return libc.ptsname(self._master).decode()
+
+
 class GDBRemoteTestBase(TestBase):
     """
     Base class for GDB client tests.
 
     This class will setup and start a mock GDB server for the test to use.
     It also provides assertPacketLogContains, which simplifies the checking
     of packets sent by the client.
     """