Fix the SIGINT handlers

[lemo]

Summary

1. Fix a data race (g_interrupt_sent flag usage was not thread safe, signals can be handled on arbitrary threads)
2. exit() is not signal-safe, replaced it with the signal-safe equivalent _exit()

[zturner]

It turns out the function this called, DispatchInputInterrupt, already acquires a mutex. Maybe put the synchronization in there? Then you don't have to reproduce the synchronization in both MI and LLDB

[clayborg]

Looks fine to me.

lldb/trunk/tools/driver/Driver.cpp

 //===-- Driver.cpp ----------------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "Driver.h"
 
+#include <atomic>
 #include <csignal>
 #include <fcntl.h>
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 // Includes for pipe()
if (isatty(STDIN_FILENO) &&
       ::ioctl(STDIN_FILENO, TIOCGWINSZ, &window_size) == 0) {
     if ((window_size.ws_col > 0) && g_driver != NULL) {
       g_driver->ResizeWindow(window_size.ws_col);
     }
   }
 }
 
 void sigint_handler(int signo) {
-  static bool g_interrupt_sent = false;
+  static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;
   if (g_driver) {
-    if (!g_interrupt_sent) {
-      g_interrupt_sent = true;
+    if (!g_interrupt_sent.test_and_set()) {
       g_driver->GetDebugger().DispatchInputInterrupt();
-      g_interrupt_sent = false;
+      g_interrupt_sent.clear();
       return;
     }
   }
 
-  exit(signo);
+  _exit(signo);
 }
 
 void sigtstp_handler(int signo) {
   if (g_driver)
     g_driver->GetDebugger().SaveInputTerminalState();
 
   signal(signo, SIG_DFL);
   kill(getpid(), signo);

lldb/trunk/tools/lldb-mi/MIDriverMain.cpp

 
 #if defined(_MSC_VER)
 #define _INC_SIGNAL // Stop window's signal.h being included -
                     // CODETAG_IOR_SIGNALS
 #endif              // _MSC_VER
 
 // Third party headers:
 #include "lldb/API/SBHostOS.h"
+#include <atomic>
 #include <csignal>
 #include <stdio.h>
 
 // In house headers:
 #include "MICmnConfig.h"
 #include "MICmnResources.h"
 #include "MICmnStreamStdin.h"
 #include "MIDriver.h"

 // Args:    vSigno  - (R) Signal number.
 // Return:  None.
 // Throws:  None.
 //--
 void sigint_handler(int vSigno) {
 #ifdef _WIN32 // Restore handler as it is not persistent on Windows
   signal(SIGINT, sigint_handler);
 #endif
-  static bool g_interrupt_sent = false;
+  static std::atomic_flag g_interrupt_sent = ATOMIC_FLAG_INIT;
   CMIDriverMgr &rDriverMgr = CMIDriverMgr::Instance();
   lldb::SBDebugger *pDebugger = rDriverMgr.DriverGetTheDebugger();
   if (pDebugger != nullptr) {
-    if (!g_interrupt_sent) {
-      g_interrupt_sent = true;
+    if (!g_interrupt_sent.test_and_set()) {
       pDebugger->DispatchInputInterrupt();
-      g_interrupt_sent = false;
+      g_interrupt_sent.clear();
     }
   }
 
   // Send signal to driver so that it can take suitable action
   rDriverMgr.DeliverSignal(vSigno);
 }
 
 //++