[Driver] Fix a segfault in signal handlers

Summary:
If we recieve a SIGCONT or SIGTSTP, while the driver is shutting down (which, sometimes, we do,
for reasons which are not completely clear to me), we would crash to due a null pointer
dereference. Guard against this situation.

Reviewers: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D18965

llvm-svn: 265958

1 files changed, 6 insertions, 2 deletions

diff --git a/lldb/tools/driver/Driver.cpp b/lldb/tools/driver/Driver.cpp
index fdf58ca5c3e..328b90beab4 100644
--- a/lldb/tools/driver/Driver.cpp
+++ b/lldb/tools/driver/Driver.cpp
@@ -1283,7 +1283,9 @@ sigint_handler (int signo)
 void
 sigtstp_handler (int signo)
 {
-    g_driver->GetDebugger().SaveInputTerminalState();
+    if (g_driver)
+        g_driver->GetDebugger().SaveInputTerminalState();
+
     signal (signo, SIG_DFL);
     kill (getpid(), signo);
     signal (signo, sigtstp_handler);
@@ -1292,7 +1294,9 @@ sigtstp_handler (int signo)
 void
 sigcont_handler (int signo)
 {
-    g_driver->GetDebugger().RestoreInputTerminalState();
+    if (g_driver)
+        g_driver->GetDebugger().RestoreInputTerminalState();
+
     signal (signo, SIG_DFL);
     kill (getpid(), signo);
     signal (signo, sigcont_handler);