Should we use std::min here (that might require a cast, iirc)? Matt ----- Original Message ----- > From: "Willem Jan Withagen" <wjw@xxxxxxxxxxx> > To: ceph-devel@xxxxxxxxxxxxxxx > Sent: Saturday, January 30, 2016 8:22:07 AM > Subject: compiling stops at od compare > > When trying to compile on CentOS 7, gcc = 4.8.3 > > os/bluestore/BlueFS.cc: In member function ‘int > BlueFS::_read(BlueFS::FileReader*, BlueFS::FileReaderBuffer*, uint64_t, > size_t, ceph::bufferlist*, char*)’: > os/bluestore/BlueFS.cc:731:31: warning: comparison between signed and > unsigned integer expressions [-Wsign-compare] > int r = MIN((int)len, left); > > This MIN is used to determine the amount of buffer that is still left > to be filed. > And here len and left are both size_t..., suggesting that both cannot be > negative. So either both need to be promoted/cast, or neither. > > The cast (int)len suggests that len could be negative. > The part where that could happen is at line 750: > > off += r; > len -= r; > ret += r; > > So there the loop exit needs len to be exactly equal to r. Even if the > loop specifies while(len>0). if len gets "negative" it grows into > something rather big. > > Now if len never gets negative then it also does not need to get cast to > int. If it does, then in the unsigned case it will always be larger than > left. > > So bottomline is that the cast serves no purpose? > Removing it fixes compilation. > > --WjW > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- -- Matt Benjamin Red Hat, Inc. 315 West Huron Street, Suite 140A Ann Arbor, Michigan 48103 http://www.redhat.com/en/technologies/storage tel. 734-707-0660 fax. 734-769-8938 cel. 734-216-5309 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
