Handle O reply packets during qRcmd

Summary:
Gdb servers like openocd may send many $O reply packets for the client to output during a qRcmd command sequence.  Currently, lldb interprets the first O packet as an unexpected response.  Besides generating no output, this causes lldb to get out of sync with future commands because it continues reading O packets from the first command as response to subsequent commands.

This patch handles any O packets during an qRcmd, treating the first non-O packet as the true response.

Preliminary discussion at http://lists.llvm.org/pipermail/lldb-dev/2018-January/013078.html

Reviewers: clayborg

Reviewed By: clayborg

Subscribers: labath, lldb-commits

Differential Revision: https://reviews.llvm.org/D41745
Patch by Owen Shaw <llvm@owenpshaw.net>

llvm-svn: 322190

1 files changed, 24 insertions, 0 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteClientBase.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteClientBase.cpp
index 4d4a4f8c5c7..62b88456b9d 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteClientBase.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteClientBase.cpp
@@ -177,6 +177,30 @@ GDBRemoteClientBase::SendPacketAndWaitForResponse(
 }
 
 GDBRemoteCommunication::PacketResult
+GDBRemoteClientBase::SendPacketAndReceiveResponseWithOutputSupport(
+    llvm::StringRef payload, StringExtractorGDBRemote &response,
+    bool send_async,
+    llvm::function_ref<void(llvm::StringRef)> output_callback) {
+  Lock lock(*this, send_async);
+  if (!lock) {
+    if (Log *log =
+            ProcessGDBRemoteLog::GetLogIfAllCategoriesSet(GDBR_LOG_PROCESS))
+      log->Printf("GDBRemoteClientBase::%s failed to get mutex, not sending "
+                  "packet '%.*s' (send_async=%d)",
+                  __FUNCTION__, int(payload.size()), payload.data(),
+                  send_async);
+    return PacketResult::ErrorSendFailed;
+  }
+
+  PacketResult packet_result = SendPacketNoLock(payload);
+  if (packet_result != PacketResult::Success)
+    return packet_result;
+
+  return ReadPacketWithOutputSupport(response, GetPacketTimeout(), true,
+                                     output_callback);
+}
+
+GDBRemoteCommunication::PacketResult
 GDBRemoteClientBase::SendPacketAndWaitForResponseNoLock(
     llvm::StringRef payload, StringExtractorGDBRemote &response) {
   PacketResult packet_result = SendPacketNoLock(payload);