vm,repl: (add ability to) break on sigint/ctrl+c

doc/api/repl.md

@@ -372,6 +372,9 @@ within the action function for commands registered using the
       equivalent to prefacing every repl statement with `'use strict'`.
     * `repl.REPL_MODE_MAGIC` - attempt to evaluates expressions in default
       mode.  If expressions fail to parse, re-try in strict mode.
+    * `breakEvalOnSigint` - Stop evaluating the current piece of code when
+      `SIGINT` is received, i.e. `Ctrl+C` is pressed. This cannot be used together
+      with a custom `eval` function. Defaults to `false`.
 
 The `repl.start()` method creates and starts a `repl.REPLServer` instance.
 

doc/api/vm.md

@@ -77,6 +77,12 @@ added: v0.3.1
   * `timeout` {number} Specifies the number of milliseconds to execute `code`
     before terminating execution. If execution is terminated, an [`Error`][]
     will be thrown.
+  * `breakOnSigint`: if `true`, the execution will be terminated when
+    `SIGINT` (Ctrl+C) is received. Existing handlers for the
+    event that have been attached via `process.on("SIGINT")` will be disabled
+    during script execution, but will continue to work after that.
+    If execution is terminated, an [`Error`][] will be thrown.
+
 
 Runs the compiled code contained by the `vm.Script` object within the given
 `contextifiedSandbox` and returns the result. Running code does not have access

lib/internal/repl.js

@@ -22,7 +22,8 @@ function createRepl(env, opts, cb) {
   opts = opts || {
     ignoreUndefined: false,
     terminal: process.stdout.isTTY,
-    useGlobal: true
+    useGlobal: true,
+    breakEvalOnSigint: true
   };
 
   if (parseInt(env.NODE_NO_READLINE)) {

lib/readline.js

@@ -182,9 +182,13 @@ Interface.prototype.setPrompt = function(prompt) {
 
 
 Interface.prototype._setRawMode = function(mode) {
+  const wasInRawMode = this.input.isRaw;
+
   if (typeof this.input.setRawMode === 'function') {
-    return this.input.setRawMode(mode);
+    this.input.setRawMode(mode);
   }
+
+  return wasInRawMode;
 };
 
 

lib/repl.js

@@ -24,6 +24,7 @@
 const internalModule = require('internal/module');
 const internalUtil = require('internal/util');
 const util = require('util');
+const utilBinding = process.binding('util');
 const inherits = util.inherits;
 const Stream = require('stream');
 const vm = require('vm');
@@ -178,7 +179,7 @@ function REPLServer(prompt,
                           replMode);
   }
 
-  var options, input, output, dom;
+  var options, input, output, dom, breakEvalOnSigint;
   if (prompt !== null && typeof prompt === 'object') {
     // an options object was given
     options = prompt;
@@ -191,10 +192,17 @@ function REPLServer(prompt,
     prompt = options.prompt;
     dom = options.domain;
     replMode = options.replMode;
+    breakEvalOnSigint = options.breakEvalOnSigint;
   } else {
     options = {};
   }
 
+  if (breakEvalOnSigint && eval_) {
+    // Allowing this would not reflect user expectations.
+    // breakEvalOnSigint affects only the behaviour of the default eval().
+    throw new Error('Cannot specify both breakEvalOnSigint and eval for REPL');
+  }
+
   var self = this;
 
   self._domain = dom || domain.create();
@@ -204,6 +212,7 @@ function REPLServer(prompt,
   self.replMode = replMode || exports.REPL_MODE_SLOPPY;
   self.underscoreAssigned = false;
   self.last = undefined;
+  self.breakEvalOnSigint = !!breakEvalOnSigint;
 
   self._inTemplateLiteral = false;
 
@@ -267,14 +276,46 @@ function REPLServer(prompt,
     regExMatcher.test(savedRegExMatches.join(sep));
 
     if (!err) {
+      // Unset raw mode during evaluation so that Ctrl+C raises a signal.
+      let previouslyInRawMode;
+      if (self.breakEvalOnSigint) {
+        // Start the SIGINT watchdog before entering raw mode so that a very
+        // quick Ctrl+C doesn’t lead to aborting the process completely.
+        utilBinding.startSigintWatchdog();
+        previouslyInRawMode = self._setRawMode(false);
+      }
+
       try {
-        if (self.useGlobal) {
-          result = script.runInThisContext({ displayErrors: false });
-        } else {
-          result = script.runInContext(context, { displayErrors: false });
+        try {
+          const scriptOptions = {
+            displayErrors: false,
+            breakOnSigint: self.breakEvalOnSigint
+          };
+
+          if (self.useGlobal) {
+            result = script.runInThisContext(scriptOptions);
+          } else {
+            result = script.runInContext(context, scriptOptions);
+          }
+        } finally {
+          if (self.breakEvalOnSigint) {
+            // Reset terminal mode to its previous value.
+            self._setRawMode(previouslyInRawMode);
+
+            // Returns true if there were pending SIGINTs *after* the script
+            // has terminated without being interrupted itself.
+            if (utilBinding.stopSigintWatchdog()) {
+              self.emit('SIGINT');
+            }
+          }
         }
       } catch (e) {
         err = e;
+        if (err.message === 'Script execution interrupted.') {
+          // The stack trace for this case is not very useful anyway.
+          Object.defineProperty(err, 'stack', { value: '' });
+        }
+
         if (err && process.domain) {
           debug('not recoverable, send to domain');
           process.domain.emit('error', err);

lib/vm.js

@@ -13,6 +13,29 @@ const Script = binding.ContextifyScript;
 // - isContext(sandbox)
 // From this we build the entire documented API.
 
+const realRunInThisContext = Script.prototype.runInThisContext;
+const realRunInContext = Script.prototype.runInContext;
+
+Script.prototype.runInThisContext = function(options) {
+  if (options && options.breakOnSigint) {
+    return sigintHandlersWrap(() => {
+      return realRunInThisContext.call(this, options);
+    });
+  } else {
+    return realRunInThisContext.call(this, options);
+  }
+};
+
+Script.prototype.runInContext = function(contextifiedSandbox, options) {
+  if (options && options.breakOnSigint) {
+    return sigintHandlersWrap(() => {
+      return realRunInContext.call(this, contextifiedSandbox, options);
+    });
+  } else {
+    return realRunInContext.call(this, contextifiedSandbox, options);
+  }
+};
+
 Script.prototype.runInNewContext = function(sandbox, options) {
   var context = exports.createContext(sandbox);
   return this.runInContext(context, options);
@@ -55,3 +78,27 @@ exports.runInThisContext = function(code, options) {
 };
 
 exports.isContext = binding.isContext;
+
+// Remove all SIGINT listeners and re-attach them after the wrapped function
+// has executed, so that caught SIGINT are handled by the listeners again.
+function sigintHandlersWrap(fn) {
+  // Using the internal list here to make sure `.once()` wrappers are used,
+  // not the original ones.
+  let sigintListeners = process._events.SIGINT;
+  if (!Array.isArray(sigintListeners))
+    sigintListeners = sigintListeners ? [sigintListeners] : [];
+  else
+    sigintListeners = sigintListeners.slice();
+
+  process.removeAllListeners('SIGINT');
+
+  try {
+    return fn();
+  } finally {
+    // Add using the public methods so that the `newListener` handler of
+    // process can re-attach the listeners.
+    for (const listener of sigintListeners) {
+      process.addListener('SIGINT', listener);
+    }
+  }
+}

src/node.cc

@@ -3239,7 +3239,7 @@ static void AtExit() {
 }
 
 
-static void SignalExit(int signo) {
+void SignalExit(int signo) {
   uv_tty_reset_mode();
 #ifdef __FreeBSD__
   // FreeBSD has a nasty bug, see RegisterSignalHandler for details
@@ -3735,9 +3735,9 @@ static void EnableDebugSignalHandler(int signo) {
 }
 
 
-static void RegisterSignalHandler(int signal,
-                                  void (*handler)(int signal),
-                                  bool reset_handler = false) {
+void RegisterSignalHandler(int signal,
+                           void (*handler)(int signal),
+                           bool reset_handler) {
   struct sigaction sa;
   memset(&sa, 0, sizeof(sa));
   sa.sa_handler = handler;

src/node_contextify.cc

@@ -553,14 +553,15 @@ class ContextifyScript : public BaseObject {
     TryCatch try_catch(args.GetIsolate());
     uint64_t timeout = GetTimeoutArg(args, 0);
     bool display_errors = GetDisplayErrorsArg(args, 0);
+    bool break_on_sigint = GetBreakOnSigintArg(args, 0);
     if (try_catch.HasCaught()) {
       try_catch.ReThrow();
       return;
     }
 
     // Do the eval within this context
     Environment* env = Environment::GetCurrent(args);
-    EvalMachine(env, timeout, display_errors, args, try_catch);
+    EvalMachine(env, timeout, display_errors, break_on_sigint, args, try_catch);
   }
 
   // args: sandbox, [options]
@@ -569,6 +570,7 @@ class ContextifyScript : public BaseObject {
 
     int64_t timeout;
     bool display_errors;
+    bool break_on_sigint;
 
     // Assemble arguments
     if (!args[0]->IsObject()) {
@@ -581,6 +583,7 @@ class ContextifyScript : public BaseObject {
       TryCatch try_catch(env->isolate());
       timeout = GetTimeoutArg(args, 1);
       display_errors = GetDisplayErrorsArg(args, 1);
+      break_on_sigint = GetBreakOnSigintArg(args, 1);
       if (try_catch.HasCaught()) {
         try_catch.ReThrow();
         return;
@@ -605,6 +608,7 @@ class ContextifyScript : public BaseObject {
       if (EvalMachine(contextify_context->env(),
                       timeout,
                       display_errors,
+                      break_on_sigint,
                       args,
                       try_catch)) {
         contextify_context->CopyProperties();
@@ -653,6 +657,23 @@ class ContextifyScript : public BaseObject {
         True(env->isolate()));
   }
 
+  static bool GetBreakOnSigintArg(const FunctionCallbackInfo<Value>& args,
+                                  const int i) {
+    if (args[i]->IsUndefined() || args[i]->IsString()) {
+      return false;
+    }
+    if (!args[i]->IsObject()) {
+      Environment::ThrowTypeError(args.GetIsolate(),
+                                  "options must be an object");
+      return false;
+    }
+
+    Local<String> key = FIXED_ONE_BYTE_STRING(args.GetIsolate(),
+                                              "breakOnSigint");
+    Local<Value> value = args[i].As<Object>()->Get(key);
+    return value->IsTrue();
+  }
+
   static int64_t GetTimeoutArg(const FunctionCallbackInfo<Value>& args,
                                const int i) {
     if (args[i]->IsUndefined() || args[i]->IsString()) {
@@ -798,6 +819,7 @@ class ContextifyScript : public BaseObject {
   static bool EvalMachine(Environment* env,
                           const int64_t timeout,
                           const bool display_errors,
+                          const bool break_on_sigint,
                           const FunctionCallbackInfo<Value>& args,
                           TryCatch& try_catch) {
     if (!ContextifyScript::InstanceOf(env, args.Holder())) {
@@ -813,16 +835,30 @@ class ContextifyScript : public BaseObject {
     Local<Script> script = unbound_script->BindToCurrentContext();
 
     Local<Value> result;
-    if (timeout != -1) {
+    bool timed_out = false;
+    if (break_on_sigint && timeout != -1) {
       Watchdog wd(env->isolate(), timeout);
+      SigintWatchdog swd(env->isolate());
       result = script->Run();
+      timed_out = wd.HasTimedOut();
+    } else if (break_on_sigint) {
+      SigintWatchdog swd(env->isolate());
+      result = script->Run();
+    } else if (timeout != -1) {
+      Watchdog wd(env->isolate(), timeout);
+      result = script->Run();
+      timed_out = wd.HasTimedOut();
     } else {
       result = script->Run();
     }
 
     if (try_catch.HasCaught() && try_catch.HasTerminated()) {
       env->isolate()->CancelTerminateExecution();
-      env->ThrowError("Script execution timed out.");
+      if (timed_out) {
+        env->ThrowError("Script execution timed out.");
+      } else {
+        env->ThrowError("Script execution interrupted.");
+      }
       try_catch.ReThrow();
       return false;
     }

src/node_internals.h

@@ -92,6 +92,13 @@ void GetSockOrPeerName(const v8::FunctionCallbackInfo<v8::Value>& args) {
   args.GetReturnValue().Set(err);
 }
 
+void SignalExit(int signo);
+#ifdef __POSIX__
+void RegisterSignalHandler(int signal,
+                           void (*handler)(int signal),
+                           bool reset_handler = false);
+#endif
+
 #ifdef _WIN32
 // emulate snprintf() on windows, _snprintf() doesn't zero-terminate the buffer
 // on overflow...

src/node_util.cc

@@ -1,4 +1,5 @@
 #include "node.h"
+#include "node_watchdog.h"
 #include "v8.h"
 #include "env.h"
 #include "env-inl.h"
@@ -98,6 +99,20 @@ static void SetHiddenValue(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+void StartSigintWatchdog(const FunctionCallbackInfo<Value>& args) {
+  int ret = SigintWatchdogHelper::GetInstance()->Start();
+  if (ret != 0) {
+    Environment* env = Environment::GetCurrent(args);
+    env->ThrowErrnoException(ret, "StartSigintWatchdog");
+  }
+}
+
+
+void StopSigintWatchdog(const FunctionCallbackInfo<Value>& args) {
+  bool had_pending_signals = SigintWatchdogHelper::GetInstance()->Stop();
+  args.GetReturnValue().Set(had_pending_signals);
+}
+
 void Initialize(Local<Object> target,
                 Local<Value> unused,
                 Local<Context> context) {
@@ -120,6 +135,9 @@ void Initialize(Local<Object> target,
   env->SetMethod(target, "getHiddenValue", GetHiddenValue);
   env->SetMethod(target, "setHiddenValue", SetHiddenValue);
   env->SetMethod(target, "getProxyDetails", GetProxyDetails);
+
+  env->SetMethod(target, "startSigintWatchdog", StartSigintWatchdog);
+  env->SetMethod(target, "stopSigintWatchdog", StopSigintWatchdog);
 }
 
 }  // namespace util