Unresolved External Symbols when using gRPC in C++

Question

Win10, Visual Studio 15 2017

That's what I've done so far:

• cloned grpc and the submodules from github
• cmake --build on grpc
• generated pb.cc and pb.h files from my proto-files
• added grpc and protobuf to VC++ Directories, Include Directories
• added zlib, grpc and protobuf to VC++ Directories, Library Directories
• added zlib.lib, gpr.lib, grpc.lib, grpc++.lib and libprotobuf.lib to Linker, Input, Additional Dependencies
• added Preprocessor Definitions: _WIN32_WINNT=0x600; NDEBUG
• changed Runtime Library to /MD

After that my empty project including the pb-files compiled without an error.

Then I wrote some code to use and test grpc but when I try to compile this time, I'm getting several errors like

LNK2019 unresolved external symbol _address_sorting_init referenced in function "void __cdecl grpc_resolver_dns_ares_init(void)" (?grpc_resolver_dns_ares_init@@YAXXZ) grpc.lib(dns_resolver_ares.obj)  
LNK2001 unresolved external symbol __imp__htons@4 grpc.lib(socket_utils_windows.obj)    
LNK2019 unresolved external symbol _ares_gethostbyname referenced in function "struct grpc_ares_request * __cdecl grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked(char const *,char const *,char const *,struct grpc_pollset_set *,struct grpc_closure *,struct grpc_lb_addresses * *,bool,char * *,struct grpc_combiner *)" (?grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked@@YAPAUgrpc_ares_request@@PBD00PAUgrpc_pollset_set@@PAUgrpc_closure@@PAPAUgrpc_lb_addresses@@_NPAPADPAUgrpc_combiner@@@Z)   grpc.lib(grpc_ares_wrapper.obj)

Answer 1

The first symbol "address_sorting_init" comes from the library address sorting present at https://github.com/grpc/grpc/tree/master/third_party/address_sorting

The second symbol is from the windows API library "ws2_32", the winsock library from Microsoft.

The third symbol is from the c-ares library: https://c-ares.haxx.se/

All 3 libraries are necessary for building grpc under Windows, so you should add them into your project.

Answer 2

The first error:

LNK2019 unresolved external symbol _address_sorting_init referenced in function "void __cdecl grpc_resolver_dns_ares_init(void)" (?grpc_resolver_dns_ares_init@@YAXXZ) grpc.lib(dns_resolver_ares.obj)  

can be resolved by adding the address_sorting.lib. This lib is in the grpc build directory, same as grpc++.lib, grpc.lib and gpr.lib.

The second error:

LNK2001 unresolved external symbol __imp__htons@4 grpc.lib(socket_utils_windows.obj)

can be resolved by adding ws2_32.lib as per Nicolas suggested.

The third error:

LNK2019 unresolved external symbol _ares_gethostbyname referenced in function "struct grpc_ares_request * __cdecl grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked(char const *,char const *,char const *,struct grpc_pollset_set *,struct grpc_closure *,struct grpc_lb_addresses * *,bool,char * *,struct grpc_combiner *)" (?grpc_dns_lookup_ares_continue_after_check_localhost_and_ip_literals_locked@@YAPAUgrpc_ares_request@@PBD00PAUgrpc_pollset_set@@PAUgrpc_closure@@PAPAUgrpc_lb_addresses@@_NPAPADPAUgrpc_combiner@@@Z)   grpc.lib(grpc_ares_wrapper.obj)

can be resolved by adding the cares.lib. You should be able to find this lib file under the third_party\cares\cares\lib directory inside the grpc build directory, no need to get it from elsewhere.

As a summary, suppose your grpc build directory is c:\grpc\.build, here are the libraries required for building a Release version application:

c:\grpc\.build\grpc++.lib
c:\grpc\.build\gpr.lib
c:\grpc\.build\grpc.lib
c:\grpc\.build\address_sorting.lib
c:\grpc\.build\third_party\protobuf\libprotobuf.lib
c:\grpc\.build\third_party\zlib.lib
c:\grpc\.build\third_party\cares\cares\lib\cares.lib
ws2_32.lib

If you want to build a Debug version of your application, please build a Debug version of grpc first, and then reference the libraries from the grpc debug version. To build a debug version with Ninja:

> md .debug
> cd .debug
> call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat" x64
> cmake .. -GNinja -DCMAKE_BUILD_TYPE=Debug
> cmake --build .

Please change above directory of vcvarsall.bat according to your Visual Studio installation.

Please also note the Debug version of protobuf library file's name is libprotobufd.lib, not libprotobuf.lib.