[lldb, lldm-mi] Fix hanging of -exec-run command.

[polyakov.alex]

Summary

-exec-run command hanged in case of invalid or dummy target.

[polyakov.alex]

These changes fix the hanging of the lldb-mi lit tests. For example:
-file-exec-and-symbols a.out
-exec-run
commands in test may cause a hanging if a.out is invalid name of binary.

[polyakov.alex]

A bit of refactoring.

[aprantl]

Nice. It should be easy to also create a test for this that just specifies an invalid filename and verifies that lldb-mi returns a failure?

[polyakov.alex]

Added the test.

[aprantl]

thanks.

tools/lldb-mi/MICmdCmdExec.cpp

 // Args:    None.
 // Return:  MIstatus::success - Functional succeeded.
 //          MIstatus::failure - Functional failed.
 // Throws:  None.
 //--
 bool CMICmdCmdExecRun::Execute() {
   CMICmnLLDBDebugSessionInfo &rSessionInfo(
       CMICmnLLDBDebugSessionInfo::Instance());
+
+  {
+    // Check we have a valid target.
+    // Note: target created via 'file-exec-and-symbols' command.
+    lldb::SBTarget sbTarget = rSessionInfo.GetTarget();
+    if (!sbTarget.IsValid() ||
+        sbTarget == rSessionInfo.GetDebugger().GetDummyTarget()) {
+      SetError(CMIUtilString::Format(MIRSRC(IDS_CMD_ERR_INVALID_TARGET_CURRENT),
+                                     m_cmdData.strMiCmd.c_str()));
+      return MIstatus::failure;
+    }
+  }
+
   lldb::SBError error;
   lldb::SBStream errMsg;
   lldb::SBLaunchInfo launchInfo = rSessionInfo.GetTarget().GetLaunchInfo();
   launchInfo.SetListener(rSessionInfo.GetListener());
 
   // Run to first instruction or main() requested?
   CMICMDBASE_GETOPTION(pArgStart, OptionLong, m_constStrArgStart);
   if (pArgStart->GetFound()) {