Fix segfaults (#1368)

* Ensure JavaScript exceptions bubble up

* Fix segfault

* Fix mutex segfault

* Fix segfault caused by memory leak

If the database was being closed, and non-exclusive work was scheduled,
it overrode the lock flag such that the state became open=false locked=false
instead of open=false locked=true. This caused queued work to not be
processed, leaking memory, which causes a segfault during napi cleanup.

Make the same changes to other methods for safe measure.

src/backup.cc

@@ -31,11 +31,10 @@ void Backup::Process() {
     }
 
     while (inited && !locked && !queue.empty()) {
-        Call* call = queue.front();
+        std::unique_ptr<Call> call(queue.front());
         queue.pop();
 
         call->callback(call->baton);
-        delete call;
     }
 }
 
@@ -86,21 +85,17 @@ void Backup::CleanQueue() {
 
         // Clear out the queue so that this object can get GC'ed.
         while (!queue.empty()) {
-            Call* call = queue.front();
+            std::unique_ptr<Call> call(queue.front());
             queue.pop();
 
-            Napi::Function cb = call->baton->callback.Value();
+            std::unique_ptr<Baton> baton(call->baton);
+            Napi::Function cb = baton->callback.Value();
 
             if (inited && !cb.IsEmpty() &&
                 cb.IsFunction()) {
                 TRY_CATCH_CALL(Value(), cb, 1, argv);
                 called = true;
             }
-
-            // We don't call the actual callback, so we have to make sure that
-            // the baton gets destroyed.
-            delete call->baton;
-            delete call;
         }
 
         // When we couldn't call a callback function, emit an error on the
@@ -113,13 +108,12 @@ void Backup::CleanQueue() {
     else while (!queue.empty()) {
         // Just delete all items in the queue; we already fired an event when
         // initializing the backup failed.
-        Call* call = queue.front();
+        std::unique_ptr<Call> call(queue.front());
         queue.pop();
 
         // We don't call the actual callback, so we have to make sure that
         // the baton gets destroyed.
         delete call->baton;
-        delete call;
     }
 }
 
@@ -220,13 +214,14 @@ void Backup::Work_Initialize(napi_env e, void* data) {
 }
 
 void Backup::Work_AfterInitialize(napi_env e, napi_status status, void* data) {
-    BACKUP_INIT(InitializeBaton);
+    std::unique_ptr<InitializeBaton> baton(static_cast<InitializeBaton*>(data));
+    Backup* backup = baton->backup;
 
     Napi::Env env = backup->Env();
     Napi::HandleScope scope(env);
 
     if (backup->status != SQLITE_OK) {
-        Error(baton);
+        Error(baton.get());
         backup->FinishAll();
     }
     else {
@@ -282,7 +277,8 @@ void Backup::Work_Step(napi_env e, void* data) {
 }
 
 void Backup::Work_AfterStep(napi_env e, napi_status status, void* data) {
-    BACKUP_INIT(StepBaton);
+    std::unique_ptr<StepBaton> baton(static_cast<StepBaton*>(data));
+    Backup* backup = baton->backup;
 
     Napi::Env env = backup->Env();
     Napi::HandleScope scope(env);
@@ -294,7 +290,7 @@ void Backup::Work_AfterStep(napi_env e, napi_status status, void* data) {
     }
 
     if (backup->status != SQLITE_OK && backup->status != SQLITE_DONE) {
-        Error(baton);
+        Error(baton.get());
     }
     else {
         // Fire callbacks.
@@ -329,7 +325,8 @@ void Backup::Work_Finish(napi_env e, void* data) {
 }
 
 void Backup::Work_AfterFinish(napi_env e, napi_status status, void* data) {
-    BACKUP_INIT(Baton);
+    std::unique_ptr<Baton> baton(static_cast<Baton*>(data));
+    Backup* backup = baton->backup;
 
     Napi::Env env = backup->Env();
     Napi::HandleScope scope(env);

src/backup.h

@@ -96,7 +96,7 @@ class Backup : public Napi::ObjectWrap<Backup> {
     static Napi::Object Init(Napi::Env env, Napi::Object exports);
 
     struct Baton {
-        napi_async_work request;
+        napi_async_work request = NULL;
         Backup* backup;
         Napi::FunctionReference callback;
 
@@ -105,6 +105,7 @@ class Backup : public Napi::ObjectWrap<Backup> {
             callback.Reset(cb_, 1);
         }
         virtual ~Baton() {
+            if (request) napi_delete_async_work(backup->Env(), request);
             backup->Unref();
             callback.Reset();
         }