C++ GRPC library for Unity3D - NULL pointer exception

[Yuval Peress]

I'm trying to use the helloworld example to create a GRPC client library for Unity3D using the following steps:

1. Took the existing GreeterClient class and modified it such that all the parameters and return types are C compatible:

    a. The constructor now takes a const char * and int to create the Channel.

    b. The SayHello function takes a const char * and returns one too.

2. I created a singleton ClientManager class with the following functions:

    a. int newClient(const char *, int port): this creates a new GreeterClient, saves it into a map and returns an int that was used as the key for the map.

    b. const char* sayHello(int client_id, const char *user): Finds the client using the client ID then calls SayHello(user).

    c. void deleteClient(int client_id): deletes the client.

3. I added an export "C" block with 3 functions to get the singleton manager instance and call its 3 functions.

To compile I'm using (note that this will create the Linux .so and OSX .bundle, I haven't gotten around to doing .dll):

$ g++ -std=c++11 -I/usr/local/include -pthread  -c -o greeter_lib.o greeter_lib.cc

$ g++ helloworld.pb.o helloworld.grpc.pb.o greeter_lib.o -L/usr/local/lib `pkg-config --libs grpc++ grpc` -lprotobuf -lpthread -ldl -shared -o greeter.so

$ g++ helloworld.pb.o helloworld.grpc.pb.o greeter_lib.o -L/usr/local/lib `pkg-config --libs grpc++ grpc` -lprotobuf -lpthread -ldl -bundle -o greeter.bundle

When I run this, calling newClient works great! When I call sayHello I get a null pointer exception:

Registered platform support modules in: 0.037474s.

Native extension for OSXStandalone target not found

Load scene 'Temp/__Backupscenes/0.backup' time: 0.633909 ms 

D0722 14:37:02.336402000 140735245529088 ev_posix.c:106] Using polling engine: poll

Receiving unhandled NULL exception

Launching bug reporter

Obtained 33 stack frames.

#0  0x000001253a96ce in helloworld::Greeter::Stub::SayHello(grpc::ClientContext*, helloworld::HelloRequest const&, helloworld::HelloReply*)

#1  0x000001253b6c04 in GreeterClient::sayHello(char const*)

#2  0x000001253b640b in GreeterClient_sayHello

#3  0x000001251d311a in  (wrapper managed-to-native) HelloWorldRpc:GreeterClient_sayHello (int,string) + 0x11a (0x1251d3000 0x1251d31fa) [0x116542660 - Unity Child Domain]

#4  0x000001251d2d4e in  HelloWorldRpc:Start () + 0x9e (0x1251d2cb0 0x1251d2e44) [0x116542660 - Unity Child Domain]

#5  0x000001219bf38a in  (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr) + 0xfa (0x1219bf290 0x1219bf4bd) [0x116542660 - Unity Child Domain]

#6  0x00000109bb90a0 in mono_get_runtime_build_info

#7  0x00000109ce73ca in mono_runtime_invoke

#8  0x0000010115e502 in ScriptingInvocation::Invoke(MonoException**, bool)

#9  0x00000101138374 in MonoBehaviour::InvokeMethodOrCoroutineChecked(ScriptingMethodMono, MonoObject*, MonoException**)

#10 0x00000101138638 in MonoBehaviour::InvokeMethodOrCoroutineChecked(ScriptingMethodMono, MonoObject*)

#11 0x00000100d2adea in DelayedCallManager::Update(int)

#12 0x00000101011e3f in PlayerLoop(bool, bool, IHookEvent*)

#13 0x000001019f92fd in Application::UpdateScene(bool)

#14 0x000001019f9873 in Application::EnterPlayMode(bool)

#15 0x000001019f6648 in Application::SetIsPlaying(bool)

#16 0x000001019f5f2a in Application::TickTimer()

#17 0x007fff940d3dec in __NSFireTimer

#18 0x007fff895cfb94 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__

#19 0x007fff895cf823 in __CFRunLoopDoTimer

#20 0x007fff895cf37a in __CFRunLoopDoTimers

#21 0x007fff895c6871 in __CFRunLoopRun

#22 0x007fff895c5ed8 in CFRunLoopRunSpecific

#23 0x007fff9b1cf935 in RunCurrentEventLoopInMode

#24 0x007fff9b1cf76f in ReceiveNextEventCommon

#25 0x007fff9b1cf5af in _BlockUntilNextEventMatchingListInModeWithFilter

#26 0x007fff9b534df6 in _DPSNextEvent

#27 0x007fff9b534226 in -[NSApplication _nextEventMatchingEventMask:untilDate:inMode:dequeue:]

#28 0x007fff9b528d80 in -[NSApplication run]

#29 0x007fff9b4f2368 in NSApplicationMain

#30 0x00000101c5a838 in EditorMain(int, char const**)

#31 0x00000101c5aee9 in main

#32 0x000001000020c4 in start

Launching external process: /Applications/Unity/Unity.app/Contents/BugReporter/Unity Bug Reporter.app/Contents/MacOS/unity.bugreporter.exe