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  1. Core Server
  2. SERVER-4536

BSONObjBuilder does not handle int64_t on LP64 data model

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    • Backwards Compatibility:
      Fully Compatible
    • Sprint:
      Integrate+Tuning 16 (06/24/16)

      Description

      The following code does not compile on Linux x86_64:

      main.cpp

      #include <mongo/client/dbclient.h>
       
      using namespace mongo;
       
      int main() {
          int64_t value = 1;
          BSONObj obj = BSON("value" << value);
      }

      Output:

      In file included from /usr/include/mongo/client/../util/../util/../db/jsobj.h:43:0,
                       from /usr/include/mongo/client/../util/../util/sock.h:25,
                       from /usr/include/mongo/client/../util/message.h:20,
                       from /usr/include/mongo/client/dbclient.h:21,
                       from main.cpp:1:
      /usr/include/mongo/client/../util/../util/../db/../bson/bson-inl.h: In member function 'mongo::BSONObjBuilder& mongo::BSONObjBuilderValueStream::operator<<(T) [with T = long int]':
      main.cpp:7:19:   instantiated from here
      /usr/include/mongo/client/../util/../util/../db/../bson/bson-inl.h:165:9: error: call of overloaded 'append(const char*&, long int&)' is ambiguous
      /usr/include/mongo/client/../util/../util/../db/../bson/bson-inl.h:165:9: note: candidates are:
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:188:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, bool)
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:196:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, int)
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:204:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, unsigned int)
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:209:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, long long int)
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:265:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, double)
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:345:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, mongo::Date_t)
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:378:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, const char*) <near match>
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:378:25: note:   no known conversion for argument 2 from 'long int' to 'const char*'
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:382:25: note: mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, const string&) <near match>
      /usr/include/mongo/client/../util/../util/../db/../bson/bsonobjbuilder.h:382:25: note:   no known conversion for argument 2 from 'long int' to 'const string& {aka const std::basic_string<char>&}'

      The problem is that MongoDB is using long long for 64 bit values. On Linux x86_64 (LP64 data model) long is used for the int64_t and boost::int64_t types and this yields to the compilation error, where long long is not considered the same 64 bit signed type as long.

      Possible solutions:

      1. Add the proper appender for the long type only for LP64 data model:

        mongo::BSONObjBuilder& mongo::BSONObjBuilder::append(const mongo::StringData&, long int);

      2. Avoid these implementation dependent data types and use exact data types from standard C99 integer types. MongoDB depends on Boost, so <boost/integer.hpp> could be used without any problem.

      I would recommend the 2nd option, because it is a clean solution. Using int, long, etc. data types might generate several unexpected issues in the future, especially when MongoDB has to be ported to various architectures.

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            Assignee:
            redbeard0531 Mathias Stearn
            Reporter:
            bszente Balint Szente
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              Updated:
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