C++ "using" declaration in Visual Studio 2008

Question

I am trying to use google protobuf and they have the following example:

using google::protobuf;

protobuf::RpcChannel* channel;
protobuf::RpcController* controller;
SearchService* service;
SearchRequest request;
SearchResponse response;

void DoSearch() {
  // You provide classes MyRpcChannel and MyRpcController, which implement
  // the abstract interfaces protobuf::RpcChannel and protobuf::RpcController.
  channel = new MyRpcChannel("somehost.example.com:1234");
  controller = new MyRpcController;

  // The protocol compiler generates the SearchService class based on the
  // definition given above.
  service = new SearchService::Stub(channel);

  // Set up the request.
  request.set_query("protocol buffers");

  // Execute the RPC.
  service->Search(controller, request, response, protobuf::NewCallback(&Done));
}

void Done() {
  delete service;
  delete channel;
  delete controller;
}

The error I am getting when I try to implement this code in Visual Studio Express 2008 is:

error C2873: 'google::protobuf' : symbol cannot be used in a using-declaration

Edit: When I do "using namespace google::protobuf;" inside of a function it no longer gives me the error. What I'm confused about is that it doesn't work the way that Google's example (and Stroustrup's in "The C++ Programming Language") seem to indicate.

Can you reference the Google example or the section of TC++PL that you are following? — CB Bailey, Feb 26 '09 at 22:43
or do you maybe mean namespace protobuf = google::protobuf; ? — Johannes Schaub - litb, Feb 26 '09 at 22:48
The Google example I'm familiar with ( http://code.google.com/apis/protocolbuffers/docs/cpptutorial.html ) only has a using declaration on namespace std. — Max Lybbert, Feb 27 '09 at 06:35

score 4 · Answer 1 · answered Feb 26 '09 at 22:27

4

google::protobuf is probably a namespace. In this case you need to do this.

using namespace google::protobuf;

answered Feb 26 '09 at 22:27

CB Bailey

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True, and possibly a bit cleaner in this situation. I wasn't sure if 'SearchService::Stub' needed protobuf qualification, though. – CB Bailey Feb 26 '09 at 22:48
true, i wonder about that too. anyway i moved my question as comment to the main question i figured it's better suited there :) – Johannes Schaub - litb Feb 26 '09 at 22:55

score 1 · Answer 2 · answered Feb 27 '09 at 05:21

Directly from the documentation:

Visual C++ Concepts: Building a C/C++ Program
Compiler Error C2873
Error Message
'symbol' : symbol cannot be used in a using-declaration
A using directive is missing a namespace keyword. This causes the compiler to misinterpret the code as a using declaration rather than a using directive.

More info on the difference.

score 0 · Answer 3 · answered Feb 18 '16 at 07:29

(1) According to Microsoft, the C2873 means;

'symbol' : symbol cannot be used in a using-declaration A using directive is missing a namespace keyword. This causes the compiler to misinterpret the code as a using declaration rather than a using directive.

(2) Also when I had C2873 with C2039 (I tried to merge CEF3 and Cinder in Visual Studio 2010), somehow I bypassed the both error by changing Properties->Configuration Properties->C/C++->Code Generation;

Enable Minimal Rebuild: Yes(/Gm), Enable C++ Exception: Yes(/EHsc), Enable Function-Level Linking: empty

C++ "using" declaration in Visual Studio 2008

3 Answers3