Kernel Release Notes

Kernel 2.6.1 (R7B)

Fixed errors and malfunctions

• A new better and more portable hash BIF, erlang:phash/2, has been introduced. The dets module will use the erlang:phash/2 for newly created tables. To rebuild an old table and start to use the new hash BIF, give the {repair,force} option to dets:open_file/2. See the documentation.
  Own Id: OTP-3397
• In OTP R7A, command line arguments could not be longer than 255 characters. This restriction has been removed again, but since the length limit on atoms is enforced more thoroughly than in earlier releases, init:get_args/0 will fail for such arguments. A new function init:get_plain_arguments/0 has been introduced, which returns strings, and should be used instead. The same problem with the command line flag -s is solved by the introduction of a new command line flag -run with the same semantics as -s, except that the user's function is called with a list of strings instead of a list of atoms.
  Own Id: OTP-3687

Improvements and new features

• On Unix, os:cmd/1 previously used a dedicated subprocess, which meant that calls to os:cmd/1 were serialized. This is no longer the case. (For R7A users: the solution in R7A was too simple; compatibility with earlier releases has been restored.) The kernel configuration parameter start_os has been removed.
  (*** POTENTIAL INCOMPATIBILITY ***)
  Own Id: OTP-3466
  Aux Id: seq4333
• A new callback Mod:prep_stop/1 has been introduced in application, for actions that need to be performed before the children are terminated.
  Own Id: OTP-3590
  Aux Id: Seq 4578
• disk_log: lclose/2 is a new function.
  Own Id: OTP-3685
• When supplying option {packet, PacketType} to gen_udp:open(Portnum, Options) it now exits with badarg. In previous releases this option was silently ignored, which was too forgiving since UDP datagrams are packets by definition, and hence this option was obsolete. Furthermore, the more exotic PacketType values, e.g. asn1, cdr, sunrm, fcgi, has never been implemented for UDP. Programs that supply this obsolete option to gen_udp:open/2 will probably crash when running on this release.
  (*** POTENTIAL INCOMPATIBILITY ***)
  Own Id: OTP-3690

Kernel 2.6 (R7A)

Known problems

• code:is_loaded/1 doesn't type check its arguments.
  Own Id: OTP-2607
• If more than 1024 bytes of text (more than 256 in release R4) are pasted into the shell, and this text consists of more than one expression sequence (each ending with a period), text after the first 1024 bytes may be lost.
  Own Id: OTP-3041

Fixed errors and malfunctions

• If an error occurred when accessing a file, the file process died, and further attempts to access the file could cause the caller to hang. Now, it will no longer hang, but return {error, terminated}.
  Own Id: OTP-1400
  Aux Id: OTP-1034, OTP-2400
• Using gen_tcp:send on a closed socket no longer causes the caller to hang.
  Own Id: OTP-2714
  Aux Id: seq 1122
• A few problems having to do with start phases in the application controller were corrected.
  Own Id: OTP-3380
  Aux Id: Seq 4166
• net_adm:names always returned the empty list. This is now corrected. A similar error was corrected in inet_db.
  Own Id: OTP-3432
  Aux Id: Seq 4274
• rpc:multicall could leave a nodedown message in the caller's message queue under some circumstances. This has been fixed.
  Own Id: OTP-3449
  Aux Id: Seq 4305
• A fix in the disk_log module: changing the size of a non-full wrap log could return the error einval.
  Own Id: OTP-3484
  Aux Id: seq4354, seq4259
• After using erlang:demonitor/1 on a remote process, a DOWN message would appear anyway if the remote node went down. This has been fixed.
  Own Id: OTP-3499
  Aux Id: Seq 4393
• global:register_name and similar functions could sometimes fail to modify the names consistently on all nodes, if new nodes appeared in the network during the operation.
  Own Id: OTP-3552
  Aux Id: Seq 4490
• If a partly partitioned net is brought together again, global could enter deadlock.
  Own Id: OTP-3575
  Aux Id: OTP-2766
• In a net which had been partly partitioned and brought together again, it could happen that the name registry would remain inconsistent indefinitely.
  Own Id: OTP-3576
• When starting up a configured network, a deadlock could occur, especially if the nodes were much different in speed. This has been fixed.
  Own Id: OTP-3625
  Aux Id: Seq 4552

Improvements and new features

• When several versions of an application existed simultaneously in the lib directory, the code server did not neccessarily pick the latest version of the application case any version number was greater than 9, when in interactive mode (for instance, 1.9 was considered later that 1.10).
  Own Id: OTP-2976
• Documentation for the function application:get_key/1/2 has been improved.
  Own Id: OTP-3379
  Aux Id: seq4164
• On Unix, os:cmd/1 previously used a dedicated subprocess, which meant that calls to os:cmd/1 were serialized. This is no longer the case.
  (*** POTENTIAL INCOMPATIBILITY ***)
  Own Id: OTP-3466
  Aux Id: seq4333
• The disk_log module has been improved as regards distribution. The value returned from open/1 when opening a distributed log has been modified. The modification is incompatible with the previously returned value. Attempts to open a distributed log on a node running new code from a node running old code, and vice versa, results in a nodedown error message. info/1 returns two more tags, 'node' and 'distributed'. The new function lclose/1 closes a log on the current node. The layout of the continuation returned from chunk{_step} has been changed, and the new function chunk_info/1 returns the node where chunks are read from. The new function accessible_logs/0 returns the names of disk logs accessible on the current node.
  (*** POTENTIAL INCOMPATIBILITY ***)
  Own Id: OTP-3531
  Aux Id: Seq 4426, Seq 4258
• The BIF erlang:monitor(process, Proc) has been extended to accept named processes, local and remote. See the documentation for erlang:monitor/2 and erlang:demonitor/1.
  Own Id: OTP-3657
• The gen_ family (mostly gen_server and gen_fsm) and rpc has been rewritten to use the new BIF erlang:monitor/2 as much as possible. This should improve performance and remove some possibilities of hanging gen_server calls. In particular, gen_server:multi_call/2..4 and rpc:multi_server_call/2,3 should now never hang, at least not when all nodes are of this release. See also the documentation for gen_server and rpc.
  Own Id: OTP-3660
• The inet driver (inet_drv, i.e the driver for (TCP&UDP)/IP) and a lot of supporting Erlang code in the application kernel, has been replaced. The new code, courtesy of Tony Rogvall, eliminates one data relay process per socket and thereby gives a throughput boost.
  Own Id: OTP-3661
• For completeness, a new function rpc:nb_yield/2 has been added. See the documentation.
  Own Id: OTP-3662
• The erlang:info/1 and erlang:system_info/1 BIFs have been merged into one. The recommended way to use the combined BIF is by the name erlang:system_info/1, but erlang:info/1 will also work.
  Own Id: OTP-3669
• There is a new os:getenv/0 function that retrieves a list of all (operating system) environment variables.
  Own Id: OTP-3670
• New socket options for TCP/IP sockets: 'tpkt' and 'line'. See the documentation for inet:setopts/2.
  Own Id: OTP-3674
• Most of the previously undocumented BIFs in the erlang module have been documented. Still undocumented are BIFs which are of no use in applications, for instance the set of BIFs used to implement the distribution protocol. The newly documented BIFs are:
  append_element/2, bump_reductions/1, display/1, function_exported/3, garbage_collect/0,1, is_builtin/3, loaded/0, make_tuple/2, md5/1, md5_final/1, md5_init/1, md5_update/2, port_close/1, port_command/2, port_connect/2, port_control/3, port_to_list/1, ref_to_list/1, system_info/1, and yield/0.
  Own Id: OTP-3675
• The new BIF term_to_binary/2 can be used for automatically compressing the external representation of an Erlang term. The binary_to_term/1 BIF in R7 automatically recognises and decompresses such compressed terms.
  Own Id: OTP-3676