Can not use grpc in an export class (my grpc service)

[liukaifei]

# Should this be an issue in the gRPC issue tracker?
Yes

# What version of gRPC and what language are you using?
1.12.x C++

# What operating system (Linux, Windows, …) and version?
Windows 10

# What runtime / compiler are you using (e.g. python version or version of gcc)
MSVC2017

# What did you do?
I am trying to build my grpc service in dll

# What did you expect to see?
I want to be ok

# What did you see instead?

## 1. use __declspec(dllexport) : error C2280

c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\xutility(2443): error C2280: 'std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>> &std::unique_ptr<_Ty,std::default_delete<_Ty>>::operator =(const std::unique_ptr<_Ty,std::default_delete<_Ty>> &)': attempting to reference a deleted function
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\memory(2309): note: see declaration of 'std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>::operator ='
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\xutility(2462): note: see reference to function template instantiation '_OutIt std::_Copy_unchecked1<_InIt,_OutIt>(_InIt,_InIt,_OutIt,std::_General_ptr_iterator_tag)' being compiled
1>        with
1>        [
1>            _OutIt=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *,
1>            _InIt=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\vector(1430): note: see reference to function template instantiation '_OutIt *std::_Copy_unchecked<_Iter,std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>*>(_InIt,_InIt,_OutIt)' being compiled
1>        with
1>        [
1>            _OutIt=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *,
1>            _Iter=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *,
1>            _Ty=grpc::internal::RpcServiceMethod,
1>            _InIt=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\vector(1448): note: see reference to function template instantiation 'void std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>::_Assign_range<_Iter>(_Iter,_Iter,std::forward_iterator_tag)' being compiled
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod,
1>            _Iter=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\vector(1448): note: see reference to function template instantiation 'void std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>::_Assign_range<_Iter>(_Iter,_Iter,std::forward_iterator_tag)' being compiled
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod,
1>            _Iter=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\vector(1471): note: see reference to function template instantiation 'void std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>::assign<std::unique_ptr<_Ty,std::default_delete<_Ty>>*,void>(_Iter,_Iter)' being compiled
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod,
1>            _Iter=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\vector(1471): note: see reference to function template instantiation 'void std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>::assign<std::unique_ptr<_Ty,std::default_delete<_Ty>>*,void>(_Iter,_Iter)' being compiled
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod,
1>            _Iter=std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<grpc::internal::RpcServiceMethod>> *
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\vector(1457): note: while compiling class template member function 'std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>> &std::vector<std::unique_ptr<_Ty,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>::operator =(const std::vector<std::unique_ptr<_Ty,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>> &)'
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod
1>        ]
1>d:\workspace\code\caxaeap\trunk\2019sp1\platform\server\configureserver\testdll\metaserviceimp.h(13): note: see reference to function template instantiation 'std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>> &std::vector<std::unique_ptr<_Ty,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>::operator =(const std::vector<std::unique_ptr<_Ty,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>> &)' being compiled
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod
1>        ]
1>d:\workspace\code\caxaeap\trunk\2019sp1\thirdmoudle\grpc\include\grpcpp\impl\codegen\service_type.h(158): note: see reference to class template instantiation 'std::vector<std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>>,std::allocator<std::unique_ptr<_Ty,std::default_delete<_Ty>>>>' being compiled
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod
1>        ]
1>c:\program files (x86)\microsoft visual studio\2017\enterprise\vc\tools\msvc\14.14.26428\include\memory(2309): note: 'std::unique_ptr<grpc::internal::RpcServiceMethod,std::default_delete<_Ty>> &std::unique_ptr<_Ty,std::default_delete<_Ty>>::operator =(const std::unique_ptr<_Ty,std::default_delete<_Ty>> &)': function was explicitly deleted
1>        with
1>        [
1>            _Ty=grpc::internal::RpcServiceMethod
1>        ]
1>Done building project "testdll.vcxproj" -- FAILED.

**## 2. do not use __declspec(dllexport) : ok

# Anything else we should know about your project / environment?

I use static grpc, protobuf, my proto library. I want my grpc service class as an export class in dll

Is there any better advice?

[sreecha]

@jtattermusch / @nicolasnoble : Do either of you have any idea about this issue?

@liukaifei : By any chance, did you already workaround this issue?

[jtattermusch]

I'm not sure I understand the question fully, but it looks like the obvious workaround it to build statically.

[sreecha]

Closing this issue due to no response from the submitter. Please reopen if needed

[bassofil]

According to https://bugs.chromium.org/p/chromium/issues/detail?id=770771#c7 the issue here seems to be that class grpc::Service does not explicitly delete the copy constructor.

[bassofil]

@sreecha I think it is better to reopen the issue, that should be simply solved by adding

Service (const Service &) = delete;
Service & operator = (const Service &) = delete;

to ::grpc::Service class.
According to https://stackoverflow.com/questions/33376021/deleted-constructor-inheritance nothing should be added to inheriting auto-generated classes.