Grpc access violation on client - c++

Question

I'm in the process of messing around with GRPC. Currently I'm using a C# web application as my GRPC server and I'm using a C++ console application as the client.
I was able to successfully connect and communicate with the server with no issue. The problem arises when
I exit the C++ console client application. Upon exiting an Access Violation is thrown.
Stack trace
MeterReaderClientCpp.exe!`anonymous namespace'::ThreadInternalsWindows::thread_body
MeterReaderClientCpp.exe!__acrt_lock
ntdll.dll!RtlpWaitOnCriticalSection()
ntdll.dll!RtlpEnterCriticalSectionContended()
ntdll.dll!RtlEnterCriticalSection()
MeterReaderClientCpp.exe!__acrt_lock(__acrt_lock_id _Lock) Line 55
MeterReaderClientCpp.exe!_free_dbg(void * block, int block_use) Line 1019
MeterReaderClientCpp.exe!free(void * block) Line 32
MeterReaderClientCpp.exe!gpr_free(void * p) Line 53
MeterReaderClientCpp.exe!`anonymous namespace'::ThreadInternalsWindows::destroy_thread() Line 142
MeterReaderClientCpp.exe!`anonymous namespace'::ThreadInternalsWindows::Join() Line 112
MeterReaderClientCpp.exe!grpc_core::Thread::Join() Line 147
MeterReaderClientCpp.exe!gc_completed_threads() Line 74
MeterReaderClientCpp.exe!stop_threads() Line 331
MeterReaderClientCpp.exe!grpc_timer_manager_set_threading(bool threaded) Line 351
MeterReaderClientCpp.exe!grpc_shutdown_internal_locked() Line 175
MeterReaderClientCpp.exe!grpc_shutdown_internal(void * __formal) Line 208
MeterReaderClientCpp.exe!`anonymous namespace'::ThreadInternalsWindows::thread_body(void * v) Line 128
GRPC Client
int main( )
{
using namespace MeterReaderWeb::Services;
using namespace google::protobuf::util;
using namespace google::protobuf;
std::cout << "Press enter\n";
std::cin.ignore( );
std::cout << "Calling Grpc service\n";
std::fstream file{ R"(C:\Certificates\certificate.cer)", std::ios::in | std::ios::beg };
if ( !file.is_open( ) )
{
std::cerr << "Failed to open file\n";
return 1;
}
std::stringstream buffer;
buffer << file.rdbuf( );
grpc::SslCredentialsOptions options;
options.pem_root_certs = buffer.str( );
auto credentials{ grpc::SslCredentials( options ) };
auto channel{ grpc::CreateChannel( "localhost:5001", credentials ) };
auto stub{ MeterReadingService::NewStub( channel ) };
ReadingPacket packet;
packet.set_status( ReadingStatus::METER_READER_SUCCESS );
packet.set_notes( "Here are some random notes" );
auto message{ packet.add_readings( ) };
message->set_customer_id( 1 );
message->set_reading_value( 10001 );
auto timestamp{ message->mutable_reading_time( ) };
timestamp->CopyFrom( TimeUtil::GetCurrentTime( ) );
grpc::ClientContext context;
StatusMessage response;
if ( auto status{ stub->AddReading( &context, packet, &response ) }; status.ok( ) )
{
std::cout << "Added reading successfully\n";
auto responseStatus{ response.status( ) };
if ( responseStatus == ReadingStatus::METER_READER_SUCCESS )
{
std::cout << "Server status: success\n"
<< "Message: " << response.message( ) << '\n';
}
}
else
{
std::cerr << "Error: " << status.error_message( ) << '\n';
std::cerr << "Error Details: " << status.error_details( ) << '\n';
}
std::cin.ignore( );
}
I heavily used the GRPC route_guide_client.cc as a guide to help me write the above application.
I've tried adding calls to both grpc_init( ) and grpc_shutdown( ) even though their client examples don't contain either calls. But adding those had no effect.
What (if anything) am I missing here? Did I forget to call/populate something that the framework is attempting to clean up upon application exit?

Answer 1

OK I believe I've found what was causing the issue.
In my original post I said:
I've tried adding calls to both grpc_init( ) and grpc_shutdown( ) even though
the client examples don't contain either calls. But
adding those had no effect."
This was true, but after re-reading the documentation for grpc_shutdown( ) i noticed this (emphasis mine):
The last call to grpc_shutdown will initiate cleaning up of grpc
library internals, which can happen in another thread. Once the
clean-up is done, no memory is used by grpc, nor are any instructions
executing within the grpc library. Prior to calling, all application
owned grpc objects must have been destroyed.
This is where I think I went wrong. I was calling grpc_shutdown() while I still had grpc objects in scope. To correct I scoped the grpc objects and then called grpc_shutdown() once that scope was exited. This seems to have corrected the issue.
New Grpc Client
int main( )
{
std::cout << "Press enter\n";
std::cin.ignore( );
std::cout << "Calling Grpc service\n";
grpc_init( );
{ // <- Intentionally added scope here.
grpc::SslCredentialsOptions options;
if ( auto certificate{ ReadCertificate( ) } )
options.pem_root_certs = std::move( certificate ).value( );
else return 1;
auto credentials{ grpc::SslCredentials( options ) };
auto channel{ grpc::CreateChannel( "localhost:5001", credentials ) };
auto stub{ MeterReadingService::NewStub( channel ) };
std::cout << "Sending single packet\n";
SendPacket( stub.get( ), 8000 );
std::cout << "Sending multiple packets\n";
StreamDiagnostics( stub.get( ), 3 );
}
std::cout << "Shutting down library\n";
grpc_shutdown_blocking( );
std::cout << "Shut down complete press enter to exit\n";
std::cin.ignore( );
}