Thursday, March 23, 2017

Difficulty using Protobuf 3.2 in C++

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I'm trying to use Protobuf in C++, but having trouble getting it to do anything meaningful. I'm using Visual Studio 2015.

I built the protobuf library. I'm using the latest version from github.

I have created a .proto file as such:

syntax = "proto3"; package Networking;   message Robot{  message KinematicLinkProto {     string name = 1;     float x_pos = 2;     float y_pos = 3;     float z_pos = 4;     float roll = 5;     float pitch = 6;     float yaw = 7;     float x_scale = 8;     float y_scale = 9;     float z_scale = 10; }  repeated KinematicLinkProto links = 1;  } 

I compile this, and try to add it to a project:

#include "Robot.pb.h"    int  main(int argc, char **argv) {      Networking::Robot robot_message;      return 0;  } 

My linker links libprotobuf.lib. I am building it as /MD and libprotobuf is built as /MD.

For some reason, this simple program has the following two linker errors:

Error   LNK2019 unresolved external symbol "private: static bool google::protobuf::io::CodedOutputStream::default_serialization_deterministic_" (?default_serialization_deterministic_@CodedOutputStream@io@protobuf@google@@0_NA) referenced in function "public: virtual unsigned char * __cdecl Networking::Robot::SerializeWithCachedSizesToArray(unsigned char *)const " (?SerializeWithCachedSizesToArray@Robot@Networking@@UEBAPEAEPEAE@Z)      Error   LNK2019 unresolved external symbol "class google::protobuf::internal::ExplicitlyConstructed<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > google::protobuf::internal::fixed_address_empty_string" (?fixed_address_empty_string@internal@protobuf@google@@3V?$ExplicitlyConstructed@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@123@A) referenced in function "protected: void __cdecl google::protobuf::internal::RepeatedPtrFieldBase::Clear<class google::protobuf::RepeatedPtrField<class Networking::Robot_KinematicLinkProto>::TypeHandler>(void)" (??$Clear@VTypeHandler@?$RepeatedPtrField@VRobot_KinematicLinkProto@Networking@@@protobuf@google@@@RepeatedPtrFieldBase@internal@protobuf@google@@IEAAXXZ)    

I'm very confused - this is a very simple program. What could I possibly be doing wrong?

EDIT: A colleague compiled proto 3001000. This version does seem to work. I'm curious as to what about 3002000 breaks everything.

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