Implement addChildProcess() to kill child processes on termination

* Implements the kill argument of OS.exec.
* Implements the automatic termination of processes spawned by OS.pipe.
* It notably kills the corresponding Tk instance when a VM terminates.

Author: eregon

vm/boostenv/main/boostvm-decl.hh

@@ -94,7 +94,11 @@ public:
 
   void addMonitor(VMIdentifier monitor);
 
+  void addChildProcess(nativeint pid);
+
 private:
+  void killChildProcesses();
+
   void notifyMonitors();
 
   void terminate();
@@ -180,6 +184,10 @@ private:
   nativeint _terminationStatus;
   std::string _terminationReason;
 
+// Spawned child processes to kill when terminating
+private:
+  std::vector<nativeint> _childProcesses;
+
 // Running thread management
 private:
   boost::asio::io_service::work* const _work;

vm/boostenv/main/boostvm.cc

@@ -28,6 +28,12 @@
 #include <boost/bind.hpp>
 #include <boost/random/random_device.hpp>
 
+#ifdef MOZART_WINDOWS
+#  include <windows.h>
+#else
+#  include <csignal>
+#endif
+
 namespace mozart { namespace boostenv {
 
 /////////////
@@ -280,6 +286,24 @@ void BoostVM::addMonitor(VMIdentifier monitor) {
   _monitors.push_back(monitor);
 }
 
+void BoostVM::addChildProcess(nativeint pid) {
+  _childProcesses.push_back(pid);
+}
+
+void BoostVM::killChildProcesses() {
+  for (auto pid : _childProcesses) {
+#ifndef MOZART_WINDOWS
+    kill(pid, SIGTERM);
+#else
+    HANDLE hProcess = OpenProcess(PROCESS_TERMINATE, FALSE, pid);
+    if (hProcess) {
+      TerminateProcess(hProcess, 0);
+      CloseHandle(hProcess);
+    }
+#endif
+  }
+}
+
 void BoostVM::notifyMonitors() {
   VMIdentifier deadVM = this->identifier;
   std::string reason = this->_terminationReason;
@@ -300,6 +324,7 @@ void BoostVM::terminate() {
   alarmTimer.cancel();
 
   portClosed = true; // close VM port
+  killChildProcesses();
   notifyMonitors();
 
   env.removeTerminatedVM(identifier, _terminationStatus, _work);

vm/boostenv/main/modos.hh

@@ -890,8 +890,7 @@ public:
       vm->deleteStaticArray(argv, argc);
 
       if (doKill) {
-        // TODO
-        // addChildProc(pid);
+        BoostVM::forVM(vm).addChildProcess(pid);
       }
 
       outPid = build(vm, pid);
@@ -1004,8 +1003,7 @@ public:
 
       vm->deleteStaticArray(argv, argc);
 
-      // TODO
-      // addChildProc(pid);
+      BoostVM::forVM(vm).addChildProcess(pid);
 
       outPid = build(vm, pid);
       outStatus = buildSharp(vm, rsock, wsock);
@@ -1092,8 +1090,7 @@ public:
 
           vm->deleteStaticArray(argv, argc);
 
-          // TODO
-          // addChildProc(pid);
+          BoostVM::forVM(vm).addChildProcess(pid);
 
           outPid = build(vm, pid);
           outStatus = std::move(ozPipe);