Given the current git head, the following file will not compile:

#include <cmath>
#include <cstring>
#include <mongo/bson/bson.h>
#include <mongo/client/connpool.h>

It fails as follows:

In file included from /afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/../util/../db/../util/optime.h:20,
from /afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/../util/../db/jsobj.h:33,
from /afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/../util/sock.h:25,
from /afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/message.h:20,
from /afs/acr/users/acm/mongo.temp.install/include/mongo/client/dbclient.h:21,
from /afs/acr/users/acm/mongo.temp.install/include/mongo/client/connpool.h:21,
from ./header_check.cc:4:
/afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/../util/../db/../util/../db/concurrency.h: In member function 'bool mongo::MongoMutex::_checkWriteLockAlready()':
/afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/../util/../db/../util/../db/concurrency.h:115: error: call of overloaded 'msgasserted(int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)' is ambiguous
/afs/acr/users/acm/mongo.temp.install/include/mongo/bson/bson.h:66: note: candidates are: void mongo::msgasserted(int, const std::string&)
/afs/acr/users/acm/mongo.temp.install/include/mongo/client/../util/assert_util.h:173: note: void mongo::msgasserted(int, std::string)