For a simple proto file:

message Person {
  required int32 id = 1;
  required string name = 2;
  optional string email = 3;
}

It's been compiled by protoc.exe and the results are used in an also simple test project, which basically does nothing but including the protoc generated files.

I'm using the msvc10 to build the test project (x64), then it gave me a lot of warning:

Warning 1   warning C4244: 'return' : conversion from '__int64' to 'int', possible loss of data D:\Work\protobuf-trunk\src\google\protobuf\descriptor.h 1441    1   testProtobuf
...
Warning 11  warning C4267: 'argument' : conversion from 'size_t' to 'int', possible loss of data    D:\Work\protobuf-trunk\src\google\protobuf\unknown_field_set.h  142 1   testProtobuf
Warning 12  warning C4267: 'return' : conversion from 'size_t' to 'int', possible loss of data  D:\Work\protobuf-trunk\src\google\protobuf\unknown_field_set.h  237 1   testProtobuf
...
Warning 14  warning C4244: '=' : conversion from '__int64' to 'int', possible loss of data  D:\Work\protobuf-trunk\src\google\protobuf\io\coded_stream.h    902 1   testProtobuf
Warning 15  warning C4244: 'return' : conversion from '__int64' to 'int', possible loss of data D:\Work\protobuf-trunk\src\google\protobuf\io\coded_stream.h    1078    1   testProtobuf
Warning 16  warning C4267: 'argument' : conversion from 'size_t' to 'google::protobuf::uint32', possible loss of data   D:\Work\protobuf-trunk\src\google\protobuf\wire_format_lite_inl.h   663 1   testProtobuf
...
Warning 19  warning C4267: 'return' : conversion from 'size_t' to 'int', possible loss of data  D:\Work\protobuf-trunk\src\google\protobuf\wire_format_lite_inl.h   739 1   testProtobuf
Warning 20  warning C4267: 'argument' : conversion from 'size_t' to 'google::protobuf::uint32', possible loss of data   D:\Work\protobuf-trunk\src\google\protobuf\wire_format_lite_inl.h   742 1   testProtobuf
Warning 21  warning C4267: 'return' : conversion from 'size_t
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