Fix TestProcesslaunch regression caused by D7372

Summary:
After closing all the leaked file descriptors to the inferior tty, the following problem occured:
- when stdin, stdout and stderr are redirected, there are no slave descriptors open (which is good)
- lldb has a reader thread, which attempts to read from the master end of the tty
- this thread receives an EOF
- in response, it closes it's master end
- as this is the last open file descriptor for the master end, this deletes the tty and sends
  SIGHUP to the inferior (this is bad)

I fix this problem by making sure the master end remains open for the duration of the inferior
process by storing a copy of the file descriptor in ProcessMonitor. I create a copy to avoid
ownership issues with the reading thread.

Reviewers: ovyalov, emaste

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D7440

llvm-svn: 228391

lldb/source/Plugins/Process/POSIX/ProcessPOSIX.cpp

@@ -252,7 +252,16 @@ ProcessPOSIX::DoLaunch (Module *module,
     if (!error.Success())
         return error;
 
-    SetSTDIOFileDescriptor(m_monitor->GetTerminalFD());
+    int terminal = m_monitor->GetTerminalFD();
+    if (terminal >= 0) {
+        // The reader thread will close the file descriptor when done, so we pass it a copy.
+        int stdio = fcntl(terminal, F_DUPFD_CLOEXEC, 0);
+        if (stdio == -1) {
+            error.SetErrorToErrno();
+            return error;
+        }
+        SetSTDIOFileDescriptor(stdio);
+    }
 
     SetID(m_monitor->GetPID());
     return error;