gRPC giving linkage errors in c++

Question

I am writing a program using gRPC in the language c++. I have installed gRPC using the command brew install grpc on a MacOS I also have the most up to date version of protobuf. When I create a basic program using gRPC I compile them using the following commands:

protoc -I=$SRC_DIR --cpp_out=$DST_DIR $SRC_DIR/test.proto Which creates the test.pb.h and test.pb.cc files

Then the command protoc -I . --grpc_out=. --plugin=protoc-gen-grpc=/usr/local/Cellar/grpc/1.45.2/bin/grpc_cpp_plugin test.proto which creates the test.pb.h and test.pb.cc files

I then run the command g++ -std=c++11 -stdlib=libc++ test.cpp test.grpc.pb.cc -L/usr/local/lib -lprotobuf to compile, where the main c++ file is test.cpp I then get some of the following linkage errors:

"grpc::ClientContext::ClientContext()", referenced from:
      MathTestClient::sendRequest(int, int) in test-e2eddc.o
  "grpc::ClientContext::~ClientContext()", referenced from:
      MathTestClient::sendRequest(int, int) in test-e2eddc.o
  "grpc::CreateChannel(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::shared_ptr<grpc::ChannelCredentials> const&)", referenced from:
      Run() in test-e2eddc.o
  "grpc::InsecureChannelCredentials()", referenced from:
      Run() in test-e2eddc.o
  "mathtest::MathRequest::MathRequest(google::protobuf::Arena*, bool)", referenced from:
      mathtest::MathRequest::MathRequest() in test-e2eddc.o
  "mathtest::MathRequest::~MathRequest()", referenced from:
      MathTestClient::sendRequest(int, int) in test-e2eddc.o

Which makes sense, judging based off the fact that in the file grcpp/impl/codgen/client_context.h the linkage errors would obviously be there because client context is defined as the following:

class ClientContext {
 public:
  ClientContext();
  ~ClientContext();

or with the CreateChannel function it is defined in create_channel.h file as

std::shared_ptr<Channel> CreateChannel(
    const grpc::string& target,
    const std::shared_ptr<ChannelCredentials>& creds);

In my main c++ file, I only use the following include from gRPC: #include <grpcpp/grpcpp.h>

Are there other include files from gRPC that I need to include which define these functions?

Answer 1

I ended up figuring out my problem if anyone else has installed grpc the same way using homebrew as I did. make sure that on top of the brew install grpc command is run that the commands brew install protobuf and brew install abseil

Next is to find out the paths of all of these using the commands brew info grpc, brew info protobuf and brew info abseil for myself personally the paths are:

/usr/local/Cellar/abseil/20211102.0

/usr/local/Cellar/grpc/1.45.2

/usr/local/Cellar/protobuf/3.19.4

Then the $PKG_CONFIG_PATH needs to be setup, if this does not already exist and there is an error if you run echo $PKG_CONFIG_PATH you can run brew install pkg-config the $PKG_CONFIG_PATH is defined by all the previous paths, with the added path of /lib/pkgconfig which then the $PKG_CONFIG_PATH can be defined as

export PKG_CONFIG_PATH=/usr/local/Cellar/grpc/1.45.2/lib/pkgconfig:/usr/local/Cellar/protobuf/3.19.4/lib/pkgconfig:/usr/local/Cellar/abseil/20211102.0/lib/pkgconfig

After that is all done, and you have the main c++ file and the proto file, mine were named test.cpp and test.proto respectively, the following commands can be run to make it compile correctly and be able to get and then run ./test

>>> protoc --cpp_out=. test.proto
>>> g++ -std=c++11 `pkg-config --cflags protobuf grpc`  -c -o test.pb.o >>> test.pb.cc
>>> protoc --grpc_out=. --plugin=protoc-gen->>> grpc=/usr/local/Cellar/grpc/1.45.2/bin/grpc_cpp_plugin test.proto
>>> g++ -std=c++11 `pkg-config --cflags protobuf grpc`  -c -o test.grpc.pb.o test.grpc.pb.cc
>>> g++ -std=c++11 `pkg-config --cflags protobuf grpc`  -c -o test.o test.cpp
>>> g++ test.pb.o test.grpc.pb.o test.o -L/usr/local/lib `pkg-config --libs >>> protobuf grpc++` -lgrpc++_reflection -ldl -o test
>>> rm test.grpc.pb.cc test.pb.cc