Work with a gdb-remote target that doesn't handle the

qWatchpointSupportInfo packet correctly.  

In GDBRemoteCommunicationClient::GetWatchpointSupportInfo,
if the response to qWatchpointSupportInfo does not
include the 'num' field, then we did not get an answer
we understood, mark this target as not supporting that
packet.

In Target.cpp, rename the very confusingly named
CheckIfWatchpointsExhausted to CheckIfWatchpointsSupported,
and check the error status returned by 
Process::GetWatchpointSupportInfo.  If we cannot determine
what the number of supported watchpoints are, assume that
they will work.  We'll handle the failure
later when we try to create/enable the watchpoint if the
Z2 packet isn't supported.

Add a gdb_remote_client test case.

<rdar://problem/42621432> 





git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@346561 91177308-0d34-0410-b5e6-96231b3b80d8

Author: jasonmolenda

packages/Python/lldbsuite/test/functionalities/gdb_remote_client/TestNoWatchpointSupportInfo.py

@@ -0,0 +1,64 @@
+from __future__ import print_function
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+from gdbclientutils import *
+
+class TestNoWatchpointSupportInfo(GDBRemoteTestBase):
+
+    @skipIfXmlSupportMissing
+    @skipIfRemote
+    def test(self):
+        """
+        Test lldb's parsing of the <architecture> tag in the target.xml register
+        description packet.
+        """
+        class MyResponder(MockGDBServerResponder):
+
+            def haltReason(self):
+                return "T02thread:1ff0d;thread-pcs:10001bc00;"
+
+            def threadStopInfo(self, threadnum):
+                if threadnum == 0x1ff0d:
+                    return "T02thread:1ff0d;thread-pcs:10001bc00;"
+
+            def setBreakpoint(self, packet):
+                if packet.startswith("Z2,"):
+                    return "OK"
+
+            def qXferRead(self, obj, annex, offset, length):
+                if annex == "target.xml":
+                    return """<?xml version="1.0"?>
+                        <target version="1.0">
+                          <architecture>i386:x86-64</architecture>
+                          <feature name="org.gnu.gdb.i386.core">
+                            <reg name="rip" bitsize="64" regnum="0" type="code_ptr" group="general"/>
+                          </feature>
+                        </target>""", False
+                else:
+                    return None, False
+
+        self.server.responder = MyResponder()
+        if self.TraceOn():
+            interp = self.dbg.GetCommandInterpreter()
+            result = lldb.SBCommandReturnObject()
+            interp.HandleCommand("log enable gdb-remote packets", result)
+        self.dbg.SetDefaultArchitecture("x86_64")
+        target = self.dbg.CreateTargetWithFileAndArch(None, None)
+
+        process = self.connect(target)
+
+        if self.TraceOn():
+            interp = self.dbg.GetCommandInterpreter()
+            result = lldb.SBCommandReturnObject()
+            interp.HandleCommand("target list", result)
+            print(result.GetOutput())
+
+	
+        err = lldb.SBError()
+        wp = target.WatchAddress(0x100, 8, False, True, err)
+        if self.TraceOn() and (err.Fail() or wp.IsValid == False):
+            strm = lldb.SBStream()
+            err.GetDescription(strm)
+            print("watchpoint failed: %s" % strm.GetData())
+        self.assertTrue(wp.IsValid())

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

@@ -1689,12 +1689,17 @@ Status GDBRemoteCommunicationClient::GetWatchpointSupportInfo(uint32_t &num) {
       m_supports_watchpoint_support_info = eLazyBoolYes;
       llvm::StringRef name;
       llvm::StringRef value;
+      bool found_num_field = false;
       while (response.GetNameColonValue(name, value)) {
         if (name.equals("num")) {
           value.getAsInteger(0, m_num_supported_hardware_watchpoints);
           num = m_num_supported_hardware_watchpoints;
+          found_num_field = true;
         }
       }
+      if (found_num_field == false) {
+        m_supports_watchpoint_support_info = eLazyBoolNo;
+      }
     } else {
       m_supports_watchpoint_support_info = eLazyBoolNo;
     }

source/Target/Target.cpp

@@ -772,10 +772,16 @@ bool Target::ProcessIsValid() {
   return (m_process_sp && m_process_sp->IsAlive());
 }
 
-static bool CheckIfWatchpointsExhausted(Target *target, Status &error) {
+static bool CheckIfWatchpointsSupported(Target *target, Status &error) {
   uint32_t num_supported_hardware_watchpoints;
   Status rc = target->GetProcessSP()->GetWatchpointSupportInfo(
       num_supported_hardware_watchpoints);
+
+  // If unable to determine the # of watchpoints available,
+  // assume they are supported.
+  if (rc.Fail())
+    return true;
+
   if (num_supported_hardware_watchpoints == 0) {
     error.SetErrorStringWithFormat(
         "Target supports (%u) hardware watchpoint slots.\n",
@@ -814,7 +820,7 @@ WatchpointSP Target::CreateWatchpoint(lldb::addr_t addr, size_t size,
     error.SetErrorStringWithFormat("invalid watchpoint type: %d", kind);
   }
 
-  if (!CheckIfWatchpointsExhausted(this, error))
+  if (!CheckIfWatchpointsSupported(this, error))
     return wp_sp;
 
   // Currently we only support one watchpoint per address, with total number of