## 1 ERTS Release Notes

This document describes the changes made to the ERTS application.

### 1.1 Erts 5.6.1

#### 1.1.1 Fixed Bugs and Malfunctions

- The SMP emulator on sparc64 erroneously used the sparc32 atomic and the sparc32 spinlock implementations which caused it to crash.
  Own Id: OTP-7006
- Call tracing the new guard BIFs byte_size, bit_size, or tuple_size and the loading a module that uses one of those functions, could cause the emulator to terminate.
  Own Id: OTP-7008
- configuring --enable-darwin-universal or --enable-darwin-64bit on MacOSX could result in a non optimized emulator. Top level configure script now corrected.
  Own Id: OTP-7014
- configuring --with-gd did not produce correct include flags for percept.
  Own Id: OTP-7015
- Environment variables weren't handled in thread safe manner in the runtime system with SMP support on Windows.
  erl_drv_putenv(), and erl_drv_getenv() has been introduced for use in drivers. Do not use putenv(), or getenv() directly in drivers. For more information see the erl_driver documentation.
  Own Id: OTP-7035
- HIPE: Corrected the choice of interface to the send/3 and setnode/3 BIFs for native-compiled code. Using the incorrect interface could, in unusual circumstances, lead to random runtime errors.
  Own Id: OTP-7067
- Garbage collections could become extremely slow when there were many keys in the process dictionary. (Thanks to Fredrik Svahn.)
  Own Id: OTP-7068
- The duplicate documentation directory in the windows installation is removed.
  Own Id: OTP-7070
- Documentation bugfixes and clarifications.
  (Thanks to Joern (opendev@gmail.com), Matthias Lang, and Richard Carlsson.) Own Id: OTP-7079
- The runtime system with SMP support not using the native atomic integer implementation part of OTP could deadlock when run on a system with more than one logical processor. That is, only the runtime system with SMP support on other hardware platforms than x86, x86_64, sparc32, and powerpc32 were effected by this bug.
  Own Id: OTP-7080
- The break handling code (run when Ctrl-C is hit) could could potentially deadlock the runtime system with SMP support.
  Own Id: OTP-7104
- The sctp driver has been updated to work against newer lksctp packages e.g 1.0.7 that uses the API spelling change adaption -> adaptation. Older lksctp (1.0.6) still work. The erlang API in gen_sctp.erl and inet_sctp.hrl now spells 'adaptation' regardless of the underlying C API.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-7120
- A bug in erlang:phash2/1 on 64-bit platforms has been fixed. (Thanks to Scott Lystig Fritchie.)
  Own Id: OTP-7127
- The emulator could under rare circumstances crash while garbage collecting.
  Own Id: OTP-7132

#### 1.1.2 Improvements and New Features

- The documentation has been updated so as to reflect the last updates of the Erlang shell as well as the minor modifications of the control sequence p of the io_lib module.
  Superfluous empty lines have been removed from code examples and from Erlang shell examples.
  Own Id: OTP-6944 Aux Id: OTP-6554, OTP-6911
- Bit syntax construction with a small integer in a non-byte aligned field wider than the CPU's word size could cause garbage bits in the beginning of the field.
  Own Id: OTP-7085
- All Windows versions older than Windows 2000 are now not supported by the Erlang runtime system. This since there was a need for usage of features introduced in Windows 2000.
  Own Id: OTP-7086
- Memory management improvements especially for the runtime system with SMP support:
  - The runtime system with SMP support can now use multiple, thread specific instances of most memory allocators. This improves performance since it reduces lock contention in the memory allocators. It may however increase memory usage for some applications. The runtime system with SMP support will by default enable this feature on most allocators. The amount of instances used can be configured.
  - driver_alloc(), driver_realloc(), and driver_free() now use their own erts specific memory allocator instead of the default malloc() implementation on the system.
  - The default configuration of some allocators have been changed to fit applications that use much memory better.
  - Some new erts_alloc configuration parameters have been added.
  - erts_alloc_config has been modified to be able to create configurations suitable for multiple instances of allocators.
  - The returned value from erlang:system_info({allocator, Alloc}) has been changed. This since an allocator may now run in multiple instances.
  If you for some reason want the memory allocators to be configured as before, you can pass the +Mea r11b command-line argument to erl.
  For more information see the erts_alloc(3), the erts_alloc_config(3), and the erlang(3) documentation.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-7100
- On Unix, denormalized floating point numbers could not be created using list_to_float/1 or binary_to_term/1. (Thanks to Matthew Dempsky.)
  Own Id: OTP-7122
- Native atomic integers and spin-locks are now also available for the runtime system with SMP support on sparc64.
  Own Id: OTP-7130
- FP exceptions support for sparc64 userspace on Linux has been added. Note that FP exception support is now turned off by default, so to actually enable it you need to do './configure --enable-fp-exceptions'.
  Own Id: OTP-7131

### 1.2 Erts 5.6

#### 1.2.1 Fixed Bugs and Malfunctions

- A bug for raw files when reading 0 bytes returning 'eof' instead of empty data has been corrected.
  Own Id: OTP-6291 Aux Id: OTP-6967
- All exported functions in gzio.c have now been renamed to avoid conflict with drivers that are indirectly linked with an external zlib library.
  Own Id: OTP-6816 Aux Id: OTP-6591
- On the 64-bit Erlang emulator, bit syntax construction with integers containing more than 60 bits ("big numbers") into fields with more than 60 bits could produce incorrect results.
  Own Id: OTP-6833
- When the runtime system failed to allocate memory for binaries, it could dead lock while writing the erl_crash.dump.
  Own Id: OTP-6848
- The runtime system with SMP support could deadlock if a process called the erlang:suspend_process(Pid) BIF or the erlang:garbage_collect(Pid) BIF while the process identified by Pid was currently running and the process calling the BIFs was terminated during the call to the BIFs.
  Processes suspending each other via the erlang:suspend_process/1 BIF or garbage collecting each other via the erlang:garbage_collect/1 BIF could deadlock each other when the runtime system with SMP support was used.
  Own Id: OTP-6920
- dbg could leave traced processes in a suspended state if the tracer process was killed with exit reason kill.
  erlang:suspend_process/2 has been introduced which accepts an option list as second argument. For more information see the erlang(3) documentation.
  Processes suspended via erlang:suspend_process/[1,2] will now be automatically resumed if the process that called erlang:suspend_process/[1,2] terminates.
  Processes could previously be suspended by one process and resumed by another unless someone was tracing the suspendee. This is not possible anymore. The process resuming a process has to be the one that suspended it.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6946
- file:write_file/3, file:write/2 and file:read/2 could crash (contrary to documentation) for odd enough file system problems, e.g write to full file system. This bug has now been corrected.
  In this process the file module has been rewritten to produce better error codes. Posix error codes now originate from the OS file system calls or are generated only for very similar causes (for example 'enomem' is generated if a memory allocation fails, and 'einval' is generated if the file handle in Erlang is a file handle but currently invalid).
  More Erlang-ish error codes are now generated. For example {error,badarg} is now returned from file:close/1 if the argument is not of a file handle type. See file(3).
  The possibility to write a single byte using file:write/2 instead of a list or binary of one byte, contradictory to the documentation, has been removed.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6967 Aux Id: OTP-6597 OTP-6291
- Monitor messages produced by the system monitor functionality, and garbage collect trace messages could contain erroneous heap and/or stack sizes when the actual heaps and/or stacks were huge.
  As of erts version 5.6 the large_heap option to erlang:system_monitor/[1,2] has been modified. The monitor message is sent if the sum of the sizes of all memory blocks allocated for all heap generations is equal to or larger than the specified size. Previously the monitor message was sent if the memory block allocated for the youngest generation was equal to or larger than the specified size.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6974 Aux Id: seq10796
- inet:getopts/2 returned random values on Windows Vista.
  Own Id: OTP-7003

#### 1.2.2 Improvements and New Features

- The emulator internal process lock implementation has been rewritten and optimized. A slight risk of starvation existed in the previous implementation. This risk has also been eliminated in the new implementation.
  Own Id: OTP-6500
- Bitstrings (bit-level) binaries and binary comprehensions are now part of the language. See the Reference Manual.
  Own Id: OTP-6558
- The windows version of erlang now has SMP support. The SMP emulator is run by default on machines which shows more than one virtual or physical processor.
  Own Id: OTP-6560 Aux Id: OTP-6925
- The details of the compressed term format has been documented in erl_ext_dist.txt. (Thanks to Daniel Goertzen.)
  Own Id: OTP-6755
- The runtime system with SMP support is now started by default if more than one logical processor are detected. For more information, see the erl(3) documentation.
  Own Id: OTP-6756
- The external format for Erlang terms and the distribution protocol are now documented in ERTS User's Guide.
  Own Id: OTP-6779
- New BIF's erlang:system_profile/1 and erlang:system_profile/2. These BIF's controls concurrency profiling options for processes, ports and schedulers.
  Own Id: OTP-6783 Aux Id: OTP-6285
- The ErlDrvTermData term types used by driver_output_term() and driver_send_term() have been extended with the term types ERL_DRV_BUF2BINARY, ERL_DRV_EXT2TERM, and ERL_DRV_UINT. ERL_DRV_BUF2BINARY is used for passing and creating a binary, ERL_DRV_EXT2TERM is used for passing terms encoded with the external term format, and ERL_DRV_UINT is used for passing unsigned integers.
  Also the data types ErlDrvUInt and ErlDrvSInt have been added which makes it more obvious how arguments to term types are interpreted with regards to width and signedness.
  The incorrect data types ErlDriverTerm, ErlDriverBinary, and ErlDriverPort in the erl_driver(3) documentation have been replaced with the correct data types ErlDrvTermData, ErlDrvBinary, and ErlDrvPort.
  For more information see the erl_driver(3) documentation.
  Own Id: OTP-6823
- Miscellaneous improvements of the erts internal thread library.
  It now support optimized atomic operations and spin-locks on windows.
  Fall-backs based on mutexes and/or spin-locks for missing optimized atomic operations, spin-locks, or rwlocks has been implemented. This makes it possible to compile the runtime system with SMP support on a lot more platforms.
  Default stack size on OpenBSD has been increased to 256 kilo-words.
  Own Id: OTP-6831 Aux Id: OTP-6560
- Many bit syntax operations, both construction and matching, are faster. For further information, see the Efficiency Guide.
  Own Id: OTP-6838
- Literal lists, tuples, and binaries are no longer constructed at run-time as they used to be, but are stored in a per-module constant pool. Literals that are used more than once are stored only once.
  This is not a change to the language, only in the details of its implementation. Therefore, the implications of this change is described in the Efficiency Guide.
  Example 1: In the expression element(BitNum-1, {1,2,4,8,16,32,64,128}), the tuple used to be constructed every time the expression was executed, which could be detrimental to performance in two ways if the expression was executed in a loop: the time to build the tuple itself and the time spent in garbage collections because the heap filled up with garbage faster.
  Example 2: Literal strings, such as "abc", used to be stored in the compiled code compactly as a byte string and expanded to a list at run-time. Now all strings will be stored expanded to lists (such as [$a,$b,$c]) in the constant pool. That means that the string will be faster to use at run-time, but that it will require more space even when not used. If space is an issue, you might want to use binary literals (that is, <<"abc">>) instead of string literals for infrequently used long strings (such as error messages).
  Own Id: OTP-6850
- The Erlang driver API has been extended with a portable POSIX thread like API for multi-threading. The Erlang driver thread API provides:
  - Threads
  - Mutexes
  - Condition variables
  - Read/Write locks
  - Thread specific data
  For more information see the erl_driver(3) documentation.
  Own Id: OTP-6857
- Recursive calls now usually consume less stack than in R11B. See the Efficiency Guide.
  Own Id: OTP-6862 Aux Id: seq10746
- The deprecated BIFs erlang:old_binary_to_term/1 and erlang:info/1 have been removed.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6876
- Calls to driver call-backs triggered by external events are now scheduled and interleaved with execution of Erlang processes also on the runtime system without SMP support.
  Own Id: OTP-6878
- Faster arithmetic of integers of more than 27 bits signed (or 60 bits signed on an 64-bit CPU), and also faster integer multiplication. (Thanks to Tony Rogvall.)
  Own Id: OTP-6891
- Significant improvements of the process_info BIFs:
  - process_info/2 can now be called with a list of items as second argument in order to atomically retrieve information about multiple items.
  - process_info/[1,2] has been optimized in the runtime system with SMP support. The whole scheduler could previously be blocked for a significant period of time in process_info/[1,2] waiting for a lock on the process being inspected. The Erlang process calling process_info/[1,2] can still be blocked for a significant period of time waiting for the lock, but the scheduler will now be able to run other processes while the process calling process_info/[1,2] waits for the lock.
  - process_info/2 now accept a few more items than before.
  - The documentation of process_info/[1,2] has been improved.
  For more information see the erlang(3) documentation.
  Own Id: OTP-6899
- open_port({}, []) could crash the emulator. (Thanks to Matthew Dempsky.)
  Own Id: OTP-6901
- Two new guard BIFs have been introduced as a recommended replacement for size/1. (The size/1 BIF will be removed no earlier than in R14B.) The BIFs are tuple_size/1 to calculate the size of a tuple and byte_size/1 to calculate the number of bytes needed for the contents of the binary or bitstring (rounded up to the nearest number of bytes if necessary).
  There is also a new bit_size/1 BIF that returns the exact number of bits that a binary or bitstring contains.
  Own Id: OTP-6902
- The ets:fixtable/2 function, which has been deprecated for several releases, has been removed.
  The ets:info/1 function has been reimplemented as a BIF, which guarantees that information returned is consistent.
  The ets:info/2 function now fails with reason badarg if the second argument is invalid. (Dialyzer can be used to find buggy code where the second argument is misspelled.)
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6906
- As the linux kernel may generate a minor fault when tracing with CPU timestamps, and there exists no patch to the Linux kernel that fixes the problem, cpu timestamps are disabled on Linux for now.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6922
- The functions io:columns/0, io:columns/1, io:rows/0 and io:rows/1 are added to allow the user to get information about the terminal geometry. The shell takes some advantage of this when formatting output. For regular files and other io-devices where height and width are not applicable, the functions return {error,enotsup}.
  Potential incompatibility: If one has written a custom io-handler, the handler has to either return an error or take care of io-requests regarding terminal height and width. Usually that is no problem as io-handlers, as a rule of thumb, should give an error reply when receiving unknown io-requests, instead of crashing.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6933
- driver_caller() can now also be used from the start callback of a driver.
  Own Id: OTP-6951
- The emulator can now be compiled for 64bit intel, as well as a 32bit universal binary on darwin/MacOSX 10.4 and 10.5.
  Own Id: OTP-6961
- If open_port fails because all available ports are already in use, it will now throw a system_limit exception instead of an enfile exception. (enfile might still be thrown if the operating system would return ENFILE.)
  Own Id: OTP-6968
- The spawn_monitor/1 and spawn_monitor/3 BIFs are now auto-imported (i.e. they no longer need an erlang: prefix).
  Own Id: OTP-6975
- On Windows, the werl window now handles resize, so that the whole window can be utilized. Text selection is also updated to be line oriented instead of rectangle oriented as in earlier versions.
  Own Id: OTP-6994 Aux Id: OTP-6933
- Kqueue support (kernel-poll) has been enabled on FreeBSD. The problem with kqueue not detecting writes on a pipe on FreeBSD was actually not a kqueue issue, but a writev on pipes issue. Neither poll(), nor select() detected the write when the bug hit. NetBSD and DragonFlyBSD probably have or have had the same bug. This bug should have been fixed in FreeBSD 6.3 and FreeBSD 7.0 thanks to Jean-Sebastien Pedron.
  Own Id: OTP-7001

### 1.3 Erts 5.5.5.5

#### 1.3.1 Fixed Bugs and Malfunctions

- Hanging writes on temporarilly unavailable NFS filesystems could cause the execution of (not file related) erlang code to get blocked even though I/O threads were used. This is now corrected.
  Own Id: OTP-6907 Aux Id: seq10771

### 1.4 Erts 5.5.5.4

#### 1.4.1 Fixed Bugs and Malfunctions

- Data passed to a driver via erlang:port_call could be corrupted when the runtime system with SMP support was used. (Thanks to YAMASHINA Hio.)
  Own Id: OTP-6879
- In the SMP emulator, if serveral processes called ets:update_counter/3 (even for different tables) when the counter values exceeded 27 bits, the counter values could be corrupted or the emulator could crash.
  Own Id: OTP-6880 Aux Id: seq10760

### 1.5 Erts 5.5.5.3

#### 1.5.1 Fixed Bugs and Malfunctions

- Creating a named table using ets:new/2 or renaming a named table using ets:rename/2 could in rare circumstances succed, meaning that there would be two or more tables with the same name. Now such call will fail with a badarg exception as it is supposed to do.
  ets:delete/1 used on a named table now removes the name immediately so that a new table with the same name can be created.
  Turning on call trace on the internal BIF that implements ets:delete/1 would crash the emulator.
  SMP emulator only: Using ets:rename/2 on a table that ets:safe_fixtable/2 has been used on could casue an emulator crash or undefined behaviour because of a missing lock.
  Own Id: OTP-6872 Aux Id: seq10756, seq10757

### 1.6 Erts 5.5.5.2

#### 1.6.1 Known Bugs and Problems

- ets:select/3 on ordered_set and with a chunksize a multiple of 1000 gave all elements instead of just 1000. Also ets:slot/2 on ordered set could give unexpected results on SMP emulator. Both problems are corrected.
  Own Id: OTP-6842

### 1.7 Erts 5.5.5.1

#### 1.7.1 Fixed Bugs and Malfunctions

- All exported functions in gzio.c have now been renamed to avoid conflict with drivers that are indirectly linked with an external zlib library.
  Own Id: OTP-6816 Aux Id: OTP-6591
- Calling binary_to_term/1 with certain invalid binaries would crash the emulator.
  Own Id: OTP-6817

#### 1.7.2 Improvements and New Features

- Restored speed of bit-syntax matching of 32 bits integers.
  Own Id: OTP-6789 Aux Id: seq10688

### 1.8 Erts 5.5.5

#### 1.8.1 Fixed Bugs and Malfunctions

- The functions in gzio.c have been renamed to avoid conflict with drivers that indirectly linked with an external zlib library.
  Own Id: OTP-6591
- The emulator without SMP support dumped core if an async-thread finished a job after the emulator had begun writing an erl_crash.dump.
  Own Id: OTP-6685
- In bit syntax matching, integer fields with greater size than 16Mb would fail to match. (Thanks to Bertil Karlsson and Francesco Pierfederici.)
  Matching out a 32-bit integer not aligned on a byte boundary from a binary could cause an heap overflow (and subsequent termination of the emulator).
  A module that contained bit syntax construction with a literal field size greater than 16Mb would fail to load.
  Several other similar bugs having to do with huge field sizes were eliminated.
  Attempting to construct a binary longer than 536870911 bytes will now fail with a system_limit exception (rather than fail in mysterious ways or construct an binary with incorrect contents). Similarily, attempting to match a binary longer than 536870911 bytes will now fail (instead of producing an incorrect result). This limitation has been documented in the Efficiency Guide. (The limit is in the 32-bit emulator; use the 64-bit emulator if you need to handle larger binaries than 536870911.)
  Own Id: OTP-6686
- Bugs in rem and div of very large numbers are corrected.
  Own Id: OTP-6692
- erlang:system_info({allocator, Alloc}) didn't allocate enough heap when a bignum was part of the result which could cause an emulator crash.
  Own Id: OTP-6693
- It was previously not possible to pass erts_alloc the same configuration via the command-line, as used by default.
  A +M* command-line argument that configure a size of some sort can now be passed a value that equals the size of the address space. The value used, in this case, will be "the size of the address space" - 1.
  Own Id: OTP-6699
- SysIOVec* driver_peekq(ErlDrvPort port, int *vlen) did not update *vlen if port was invalid. *vlen is now set to -1 if the port is invalid.
  The efile driver expects *vlen to be updated also when the port is invalid. This situation occurs seldom, but when the runtime system has async-threads enabled and ports are killed it can. When it occured the runtime system crashed.
  Own Id: OTP-6729

#### 1.8.2 Improvements and New Features

- For scripts written using escript, there is a new function escript:script_name/0, which can be used to retrieve the pathame of the script. The documentation has been clarified regarding pre-defined macros such as ?MODULE and the module name.
  Own Id: OTP-6593
- The section Guards in the chapter The Abstract Format of the ERTS User's Guide has been updated.
  Own Id: OTP-6600
- Corrected protocol layer flue for socket options SO_LINGER, SO_SNDBUF and SO_RCVBUF, for SCTP.
  Own Id: OTP-6625 Aux Id: OTP-6336
- The behaviour of the inet option {active,once} on peer close is improved and documented.
  Own Id: OTP-6681
- The inet option send_timeout for connection oriented sockets is added to allow for timeouts in communicating send requests to the underlying TCP stack.
  Own Id: OTP-6684 Aux Id: seq10637 OTP-6681
- The command line flag -args_file FileName, and the environment variables ERL_AFLAGS, and ERL_ZFLAGS for the erl command have been added. For more information see the erl(1) documentation.
  Own Id: OTP-6697
- The is_constant/1 type test has been deprecated. is_constant/1 is improperly named and almost entirely undocumented.
  Own Id: OTP-6731

### 1.9 Erts 5.5.4.3

#### 1.9.1 Fixed Bugs and Malfunctions

- process_flag(trap_exit, Bad) where Bad was a term not equal to true or false, didn't fail with badarg as it should; instead, the failure was silently ignored. This bug was introduced in erts-5.5.2.
  Own Id: OTP-6627 Aux Id: OTP-6160
- The minimum and default stack size for async-threads has been increased to 16 kilowords. This since the previous minimum and default stack size of 8 kilowords proved to be too small (introduced in erts-5.5.4.2).
  Own Id: OTP-6628 Aux Id: OTP-6580, Seq10633

#### 1.9.2 Improvements and New Features

- process_flag/2 accepts the new flag sensitive.
  Own Id: OTP-6592 Aux Id: seq10555

### 1.10 Erts 5.5.4.2

#### 1.10.1 Fixed Bugs and Malfunctions

- When a port steals control over a file descriptor from another port, the stealing port tests if the other port is alive. This in order to be able to give an accurate error message. In the runtime system with SMP support, this test was done without appropriate locks held. This could in worst case lead to an erroneous error message; therefore, this bug is to be considered harmless.
  Own Id: OTP-6602

#### 1.10.2 Improvements and New Features

- The default stack size for threads in the async-thread pool has been shrunk to 8 kilowords, i.e., 32 KB on 32-bit architectures. This small default size has been chosen since the amount of async-threads might be quite large. The default stack size is enough for drivers delivered with Erlang/OTP, but might not be sufficiently large for other dynamically linked in drivers that use the driver_async() functionality. A suggested stack size for threads in the async-thread pool can be configured via the +a command line argument of erl(1).
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6580

### 1.11 Erts 5.5.4.1

#### 1.11.1 Fixed Bugs and Malfunctions

- Setting the time on the system while using heart on a linux machine where the emulator was built with clock_gettime support (default from Linux 2.6/erts-5.5.4 and upwards), could make the heart command fire. This was due to bug in the heart executable which is now corrected.
  Own Id: OTP-6598 Aux Id: seq10614

### 1.12 Erts 5.5.4

#### 1.12.1 Fixed Bugs and Malfunctions

- Corrected misspelling of '-pz' in the help text for erlc. (Thanks to Ulf Wiger.)
  Own Id: OTP-6433
- The MD5 calculation of a BEAM file done by code:module_md5/1, beam_lib:md5/1, and by the compiler for the default value of the vsn attribute have all been changed so that its result will be the same on all platforms; modules containing funs could get different MD5s on different platforms.
  Own Id: OTP-6459
- The emulator could dump core while writing an erl_crash.dump file if there were funs with a large terms in its environment. Since there is no way to inspect a fun's environment in the crashdump_viewer application anyway, a variables in the environment are now set to [] before dumping the fun. (Thanks to Jean-Sebastien Pedron.)
  Own Id: OTP-6504
- {Port, {exit_status, S}} messages from ports opened with the exit_status option could under rare circumstances be delayed. This bug was present on Erlang runtime systems without SMP support on all unix operating systems other than SunOS.
  Own Id: OTP-6528
- A bug in linuxthreads could cause the emulator to dump core when dlerror() was called before the first call to dlopen(). As a workaround the emulator always makes a call to dlopen() on initialization when linuxthreads is used as thread library.
  Own Id: OTP-6530
- file:sync/1 did not do anything on Windows. Now it calls the system function for flushing buffers (FlushFileBuffers()). (Thanks to Matthew Sackman.)
  Own Id: OTP-6531
- open_port/2 could on the runtime system with SMP support fail with the wrong exit reason when a port couldn't be created. When this happened the exit reason was typically eintr, or ebusy instead of eagain.
  Own Id: OTP-6536
- The file driver (efile_drv) did not flush data written using the option 'delayed_write' after the set timeout time, rather at the next file operation. This bug has now been corrected.
  Own Id: OTP-6538

#### 1.12.2 Improvements and New Features

- An interface towards the SCTP Socket API Extensions has been implemented.It is an Open Source patch courtesy of Serge Aleynikov and Leonid Timochouk. The Erlang code parts has been adapted by the OTP team, changing the Erlang API somewhat.
  The Erlang interface consists of the module gen_sctp and an include file -include_lib("kernel/include/inet_sctp.hrl"). for option record definitions. The gen_sctp module is documented.
  The delivered Open Source patch, before the OTP team rewrites, was written according to http://tools.ietf.org/html/draft-ietf-tsvwg-sctpsocket-13 and was claimed to work fine, tested on Linux Fedora Core 5.0 (kernel 2.6.15-2054 or later) and on Solaris 10 and 11. The OTP team rewrites used the same standard document but might have accidentally broken some functionality. If so it will soon be patched to working state. The tricky parts in C and the general design has essentially not changed. During the rewrites the code was hand tested on SuSE Linux Enterprise Server 10, and briefly on Solaris 10. Feedbach on code and docs is very much appreciated.
  The SCTP interface is in beta state. It has only been hand tested and has no automatic test suites in OPT meaning everything is most certainly not tested. Socket active mode is broken. IPv6 is not tested. The documentation has been reworked due to the API changes, but has not been proofread after this.
  Thank you from the OTP team to Serge Aleynikov and Leonid Timochouk for a valuable contribution. We hope we have not messed it up too much.
  Own Id: OTP-6336
- A {minor_version,Version} option is now recognized by term_to_binary/2. {minor_version,1} will cause floats to be encoded in an exact and more space-efficient way compared to the previous encoding.
  Own Id: OTP-6434
- There is a new escript program that can be used for writing scripts in Erlang. Erlang scripts don't need to be compiled and any arguments can be passed to them without risk that they are interpreted by the Erlang system.
  Own Id: OTP-6505
- Setting and getting socket options in a "raw" fashion is now allowed. Using this feature will inevitably produce non portable code, but will allow setting ang getting arbitrary uncommon options on TCP stacks that do have them.
  Own Id: OTP-6519
- Miscellaneous signal handling improvements on the Erlang runtime system with SMP support.
  The fallback implementation of spin locks and atomic operations are now implemented using pthread spin locks when pthread spin locks are found on the system.
  The Erlang runtime system with SMP support can now run on Linux systems that has Linuxthreads instead of NPTL (Native POSIX Thread Library). Note that the SMP support hasn't been as thoroughly tested with Linuxthreads as with NPTL. A runtime system with SMP support will therefore not be built by default on Linux when NPTL isn't found. In order to force a build of the runtime system with SMP support, pass --enable-smp-support to configure when building OTP.
  Own Id: OTP-6525

### 1.13 Erts 5.5.3.1

#### 1.13.1 Fixed Bugs and Malfunctions

- erlang:system_flag(multi_scheduling, block) could cause the emulator with SMP support to deadlock.
  Own Id: OTP-6431 Aux Id: OTP-6403
- The runtime system with SMP support failed to call the driver timeout callback of ports in state closing. This could cause ports to fail flushing their I/O queues.
  Own Id: OTP-6432
- The {Port, closed} message from a closed port could arrive at the port owner before Port had been removed from the result of erlang:ports/0 in the runtime system with SMP support.
  Own Id: OTP-6437
- The async id of async jobs created via driver_async wasn't created in a thread safe manner in the runtime system with SMP support. This could in worst case cause driver_async_cancel() to cancel another async job than intended.
  Own Id: OTP-6438
- Under rare circumstances a terminating connection between two nodes could cause an instantaneous reconnect between the two nodes to fail on the runtime system with SMP support.
  Own Id: OTP-6447
- In the documentation of the driver entry field extended_marker of erts version 5.5.3 (driver_entry(3)), the following is stated: "The following fields are ignored if this field is equal to 0". This is a documentation bug and has been changed to: "If this field is equal to 0, all the fields following this field also have to be 0, or NULL in case it is a pointer field".
  The runtime check for detection of old incompatible drivers made when loading drivers has been improved. The emulator can, however, not make sure that a driver that doesn't use the extended driver interface isn't incompatible. Therefore, when loading a driver that doesn't use the extended driver interface, there is a risk that it will be loaded also when the driver is incompatible. When the driver use the extended driver interface, the emulator can verify that it isn't of an incompatible driver version. You are therefore advised to use the extended driver interface.
  For more information see the erl_driver(3) and driver_entry(3) documentation.
  Own Id: OTP-6452 Aux Id: OTP-6330
- When terminating ports on the runtime system with SMP support, removal of links to processes was done without locking the link lock on processes. This could cause an emulator crash.
  Own Id: OTP-6475
- The emulator with SMP support could crash when a port flushed its I/O queue by calling driver_async() from the timeout driver callback.
  Own Id: OTP-6479
- Large exit reasons could under rare circumstances cause the runtime system with SMP support to crash.
  Own Id: OTP-6521

#### 1.13.2 Improvements and New Features

- Faster system calls for keeping the time accurate are used on newer Linux kernels, which can result in a significant speed-up of the emulator on those systems.
  Own Id: OTP-6430
- Added number of async threads and number of scheduler threads to the system information that can be retrieved via driver_system_info(). For more information see the erl_driver(3) documentation.
  Own Id: OTP-6440
- When SIGUSR1 is received by the runtime system with SMP support, the erl_crash.dump is now written by a special thread, instead of as before directly from the signal handler.
  Own Id: OTP-6465
- term_to_binary/2 with compression is now faster.
  term_to_binary/2 now accepts the option '{compressed,Level}' for specifying the compression level. Level must be in the range 0 (no compression) through 9 (highest compression level). Default is 6.
  Future compatibility bugfix: binary_to_term/1 did not handle the Uniq and Index fields correctly.
  Own Id: OTP-6494
- Removed unnecessary reallocation when initializing kernel-poll set.
  Own Id: OTP-6516

### 1.14 Erts 5.5.3

#### 1.14.1 Fixed Bugs and Malfunctions

- Node and fun table entries could under rare circumstances be deallocated multiple times on the emulator with SMP support.
  Own Id: OTP-6369
- epoll_wait() can repeat entries for the same file descriptor in the result array. This could cause the ready_input, ready_output, or event callbacks of a driver to unintentionally be called multiple times. We have only noted repeated entries when an error condition has occurred on the file descriptor. In this case, the repeated entries should normally not be a problem for the driver since it should detect the error and de-select the file descriptor. Therefore this bug should be considered harmless. The emulator now coalesce repeated entries into one.
  You are only affected by this bug if you are using erts-5.5.2.* and the kernel-poll feature on linux.
  Own Id: OTP-6376 Aux Id: OTP-6222
- If a process that was waiting in gen_tcp:accept/1 was killed, calling gen_tcp:accept/1 again on the same listen socket would fail with '{error,einval}'.
  Own Id: OTP-6381 Aux Id: seq10535
- The emulator failed to start on Solaris 10 when kernel-poll support was enabled and the maximum number of filedescriptors configured was less than or equal to 256.
  Own Id: OTP-6384 Aux Id: OTP-6222
- The R10B compiler could generate unsafe bs_save/bs_restore instructions that could cause memory corruption. (The R11B compiler does not have that problem.) The erlang emulator will now refuse to load R10B-compiled modules that contain such unsafe bs_save/bs_restore instructions. In addition, the beam_validator module in the compiler will also reject such instructions (in case it is used to validate R10B code). (Thanks to Matthew Reilly.)
  Own Id: OTP-6386
- Process and port timers could fail to work properly on the runtime system with SMP support. Many thanks to Dmitriy Kargapolov and Serge Aleynikov who tracked down this bug.
  Own Id: OTP-6387
- Bit syntax code compiled by an R10B compiler that matched out a floating point number would not properly check that the floating point number was valid; if the float was, for instance, NaN the emulator could crash.
  Own Id: OTP-6395
- statistics(runtime) on Windows used to return the elapsed system time for the process, instead of the user time. Corrected. (Thanks to Robert Virding.)
  Own Id: OTP-6407
- A loadable driver (loaded by erl_ddll) which used driver_async() would cause the emulator to crash. (Thanks to Dmitriy Kargapolov.)
  Own Id: OTP-6410
- Under rare circumstances the emulator on unix platforms could fail to terminate the Erlang port corresponding to a port program opened with the exit_status option.
  Own Id: OTP-6411
- A link removed via unlink/1 could under rare circumstances transfer exit signals for a short period of time after the call to unlink/1 had returned when the runtime system with SMP support was used.
  Own Id: OTP-6425 Aux Id: OTP-6160

#### 1.14.2 Improvements and New Features

- In the runtime system with SMP support, ports are now being scheduled on the scheduler threads interleaved with processes instead of being run in a separate I/O thread.
  Own Id: OTP-6262
- More interfaces are added in erl_ddll, to support different usage scenarios.
  Own Id: OTP-6307 Aux Id: OTP-6234
- In the runtime system with SMP support, the global I/O lock has been replaced with a more fine grained port locking scheme. Port locking is either done on driver level, i.e., all ports executing the same driver share a lock, or on port level, i.e., each port has its own lock. Currently the inet driver, the efile driver, and the spawn driver use port level locking and all other statically linked in drivers use driver level locking. By default dynamically linked in drivers will use locking on driver level. For more information on how to enable port level locking see the erl_driver(3) and the driver_entry(3) man pages.
  As of erts version 5.5.3 the driver interface has been extended. The extended interface introduce version management, the possibility to pass capability flags to the runtime system at driver initialization, and some new driver API functions. For example, the driver_system_info() function which can be used to determine if the driver is run in a runtime system with SMP support or not. The extended interface doesn't have to be used, but dynamically linked in driver have to be recompiled. For information see the erl_driver(3) and the driver_entry(3) man pages.
  NOTE: Dynamically linked in drivers have to be recompiled.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6330 Aux Id: OTP-6262
- A test and debug feature which modifies the timing of the runtime system has been added. For more information, see documentation of the +T<Level> command line argument of erl(1).
  Own Id: OTP-6382
- The version of zlib (http://zlib.net) linked into run-time system has been updated to version 1.2.3.
  Own Id: OTP-6394
- The erlc program now passes on the -smp and -hybrid options to the Erlang emulator it starts. This is mainly useful for compiling native code, because native code must be compiled with same type of run-time system as in which it will be run.
  If the -s option is given, erlc now prints a warning that it is deprecated and that it will be removed in R12B.
  Own Id: OTP-6398
- The schedulers option of erlang:system_flag/2 has been removed, i.e., the number of scheduler threads cannot be changed after emulator boot time any more.
  A multi_scheduling option has been added to erlang:system_flag/2. This option can be used for blocking and unblocking multi-scheduling. For more information see the erlang(3) documentation.
  Own Id: OTP-6403
- A port program that had been started with the exit_status option and closed one of the pipes used for communication with the emulator caused the emulator to continuously poll for termination of the port program. This only became a problem when the emulator didn't have other things to do and the port program closed a pipe much earlier than it terminated. When the emulator had other things to do, such as running Erlang processes, the emulator polled for termination in between scheduling of processes.
  Now the emulator doesn't poll for termination of the port program at all; instead, it waits for the child signal from the terminated port program to arrive and then schedules the Erlang port for termination.
  The termination of any port programs have also been optimized. Previously the termination of any port program did always cause a scan of a table of the size equal to maximum number of file descriptors. If the maximum number of file descriptors was large, this scan could be quite expensive. Now the search have been reduced to the set of ports started with the exit_status option.
  Note, all of the above only applies to Erlang emulators on Unix platforms.
  Own Id: OTP-6412 Aux Id: seq10194
- * BEAM: added support for floating-point exceptions on FreeBSD (32-bit x86)
  * SMP: made locking procedures work even when native lock operations aren't implemented
  * SMP: improved timing accuracy in the timer thread (if enabled)
  Own Id: OTP-6424

### 1.15 Erts 5.5.2.2

#### 1.15.1 Fixed Bugs and Malfunctions

- A bug in the kernel poll implementation could cause the emulator to omit polling for events on file descriptors. The bug was only present when using the kernel poll implementation based on epoll or kqueue. This bug was introduced in erts-5.5.2.
  Own Id: OTP-6344 Aux Id: OTP-6222

### 1.16 Erts 5.5.2.1

#### 1.16.1 Fixed Bugs and Malfunctions

- The run_erl program now aquires its psedo-ttys using openpty(3), so that it will work on newer Linux distributions that don't have the traditional pseudo-tty devices in the file system. On platforms that don't have openpty(3), run_erl will still search for pseudo-tty devices in the file system.
  The run_erl program will now wait using waitpid(3) to prevent the program it spawned to become defunct. run_erl will also terminate after a delay of 5 seconds (to allow any pending output to be written to the log file) if the spawned program terminates even if some child of it still holds stdin and/or stdout open.
  Own Id: OTP-6225 Aux Id: seq10500
- A bug in ordered_set ETS datatyp caused ets:select (and match) to return faulty results when the table contained process id's from another node.
  Own Id: OTP-6338

### 1.17 Erts 5.5.2

#### 1.17.1 Fixed Bugs and Malfunctions

- erlc: A typo in the help text for '-pa path' was corrected.
  Own Id: OTP-6218
- Failure in port command/control driver callbacks could crash the non-SMP emulator. This bug was introduced in the 5.5 version of erts.
  Own Id: OTP-6224
- Erroneous "Input driver gone away without deselecting!" error reports could sometimes occur when a driver instance terminated in the ready_output() callback of the driver. This bug was only present in emulators that used poll(). Note, that this bug was harmless, the only effect it had was the erroneous error report.
  Own Id: OTP-6229 Aux Id: OTP-3993, Seq5266, Seq7247, OTP-4307
- The emulator could cause a type assertion failure while writing an erl_crash.dump, causing the erl_crash.dump to be terminated and a core dump generated.
  Own Id: OTP-6235 Aux Id: seq10444
- The registered name of a process is now the last observable resource removed before links and monitors are triggered when a process terminates.
  Previously ets tables were removed after the registered name. This could cause problems on the runtime system with SMP support for code that expected that ets tables owned by a specific process had been removed if the name of the process had been removed.
  Own Id: OTP-6237
- Failure to fork() a new (os) process could cause the emulator to deadlock. This bug affect all emulators with SMP support, and emulators with async thread support on SunOS.
  Own Id: OTP-6241 Aux Id: OTP-3906
- Fprof traces could become truncated for the SMP emulator. This bug has now been corrected.
  Own Id: OTP-6246
- The undocumented functions inet:getiflist/0,1 inet:ifget/2,3 and inet:getif/1 were completely broken on Windows. That has been fixed.
  Own Id: OTP-6255
- Behavior in case of disappeared nodes when using the dist_auto_connect once got changed in R11B-1. The timeouts regarding normal distributed operationes is now reverted to the old (pre R11B-1).
  Own Id: OTP-6258 Aux Id: OTP-6200, seq10449
- The bsl and bsr operators could cause the emulator to crash if given invalid arguments. (Thanks to datacompboy and Per Gustafsson.)
  Own Id: OTP-6259
- driver_cancel_timer() could under certain circumstances fail to cancel the timer on the runtime system with SMP support.
  Own Id: OTP-6261
- A call to erlang:system_info(info) could deadlock the runtime system with SMP support.
  Own Id: OTP-6268

#### 1.17.2 Improvements and New Features

- Exit signals are now truly asynchronous in the runtime system with SMP support. This simplifies locking in bifs a lot, and makes process termination cheaper.
  Own Id: OTP-6160
- When tracing on the runtime system with SMP support it can be difficult to know when a trace has been delivered to the tracer. A new built in function erlang:trace_delivered/1 has been introduced in order to make it easier to know when the trace has been delivered. See the erlang(3) man page for more information.
  Own Id: OTP-6205 Aux Id: OTP-6269
- Kernel poll support can now be combined with SMP support. Currently the following kernel poll versions exist: /dev/poll, epoll, and kqueue. Linux kpoll has been replaced with epoll. Some time in the future there will also be a kernel poll version using Solaris event ports.
  The "check io" implementation for unix has been completely rewritten. The current kernel poll implementation reduce the amount of system calls needed compared to the old kernel poll implementation.
  When epoll or kqueue is used either poll or select is used as fallback. Previously only poll could be used as fallback. Since select now can be used as fallback, kernel poll support is now also available on newer MacOSX. Note however, when select is used as fallback, the maximum number of file descriptors is limited to FD_SETSIZE.
  Kernel poll support is now enabled by default if /dev/poll, epoll, or kqueue is found when building OTP, i.e. you do not have to pass the --enable-kernel-poll argument to configure. As before, kernel poll is disabled by default in the runtime system. In order to enable it, pass the +Ktrue command line argument to erl.
  Note: configure will refuse to enable kernel poll support on FreeBSD since kqueue have problems with (at least) pipes on all version of FreeBSD that we have tested.
  Own Id: OTP-6222 Aux Id: seq10380
- The erl_ddll module and the code in the emulator have been completely rewritten; several bugs were fixed.
  Own Id: OTP-6234
- The SMP emulator now avoids locking for the following operations (thus making them as fast as in the UP emulator): atom_to_list/1, atom comparision, atom hashing, erlang:apply/3.
  Own Id: OTP-6252
- There are new BIFs erlang:spawn_monitor/1,3, and the new option monitor for spawn_opt/2,3,4,5.
  The observer_backend module has been updated to handle the new BIFs.
  Own Id: OTP-6281

### 1.18 Erts 5.5.1.1

#### 1.18.1 Improvements and New Features

- There is now an option read_packets for UDP sockets that sets the maximum number of UDP packets that will be read for each invocation of the socket driver.
  Own Id: OTP-6249 Aux Id: seq10452

### 1.19 Erts 5.5.1

#### 1.19.1 Fixed Bugs and Malfunctions

- Complex pattern matching of strings would fail in the 64 bits emulator because of a bug in the loader. (Thanks to Igor Goryachev.)
  Own Id: OTP-6142
- -134217728 div 134217728 and -134217728 rem 134217728 would be calculated incorrectly. abs(-2147483648) could in unlucky circumstances cause a heap overflow, as could size(Binary) when size of the binary was larger than 128Mb.
  Own Id: OTP-6154
- erlang:display/1 displayed erroneous values for negative integers.
  Big integers (both positive and negative) were previously displayed in hexadecimal form while small integers were displayed in decimal form. All integers are now displayed in decimal form.
  NOTE: erlang:display/1 should only be used for debugging.
  Own Id: OTP-6156
- A call to erlang:trace/3 with erroneous flags caused the SMP emulator to deadlock instead of exiting the calling process with badarg.
  Own Id: OTP-6175
- A bug causing the emulator to hang when exiting a process that is exception traced has been fixed.
  Own Id: OTP-6180
- ets:rename/1 could deadlock, or crash the SMP emulator when the table wasn't a named table.
  ets:next/2, and ets:prev/2 could return erroneous results on the SMP emulator.
  Own Id: OTP-6198 Aux Id: seq10392, seq10415
- A memory allocation bug could cause the SMP emulator to crash when a process had executed a receive after with a larger timeout than 10 minutes.
  Own Id: OTP-6199
- The runtime system with SMP support did not slowly adjust it's view of time when the system time suddenly changed.
  Timeouts could sometimes timeout too early on the runtime system with SMP support.
  Own Id: OTP-6202

#### 1.19.2 Improvements and New Features

- The smp runtime system now automatically detects the number of logical processors on MacOSX (darwin) and OpenBSD.
  The smp runtime system is now built by default on MacOSX (darwin) on x86.
  Own Id: OTP-6119
- The -smp command line argument now take the following options: enable, auto, or disable.
  Especially the -smpauto argument is useful since it starts the Erlang runtime system with SMP support if it is available and more than one logical processor are detected; otherwise, it starts the Erlang runtime system without SMP support. For more information see the erl(1) man page.
  Own Id: OTP-6126
- Increased the reduction cost for sending messages in the SMP emulator so it behaves more like the non-SMP emulator.
  Own Id: OTP-6196
- A port running a dynamically linked-in driver that exits due to the driver being unloaded now exits with exit reason driver_unloaded. Previously the port exited with exit reason -1.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6204
- Changed name of the erlang:system_info/1 argument scheduler to scheduler_id. This since the scheduler argument so easily could be mixed up with the schedulers argument (both returning integers).
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6208
- The changes below were made by Mikael Pettersson, HiPE.
  HiPE runtime system:
  Reduce overheads in the HiPE runtime system's BIF glue code.
  Fix bug when exceptions are thrown from BEAM to HiPE.
  Support SPARC on Linux.
  Support x86 on FreeBSD.
  Floating-point exceptions:
  Reduce overheads in checking results of floating-point operations.
  Minor bug fix in SSE2 floating-point exception handling.
  Support SSE2 floating-point exceptions on 32-bit x86 machines.
  Make FP exceptions work in the SMP runtime system on FreeBSD/x86.
  Support floating-point exceptions on SPARCs running Linux.
  Runtime system:
  Minor scheduler optimisation in the non-SMP runtime system.
  Substantial reduction of I/O thread overheads in the SMP runtime system if the separate timer thread is used. (In R11B-1, the separate timer thread is not used.)
  Own Id: OTP-6211

### 1.20 ERTS 5.5

#### 1.20.1 Fixed Bugs and Malfunctions

- Previously unlink/1 and erlang:demonitor/2 behaved completely asynchronous. This had one undesirable effect, though. You could never know when you were guaranteed not to be affected by a link that you had unlinked or a monitor that you had demonitored.
  The new behavior of unlink/1 and erlang:demonitor/2 can be viewed as two operations performed atomically. Asynchronously send an unlink signal or a demonitor signal, and ignore any future results of the link or monitor.
  NOTE: This change can cause some obscure code to fail which previously did not. For example, the following code might hang:

                  Mon = erlang:monitor(process, Pid),
                  %% ...
                  exit(Pid, bang),
                  erlang:demonitor(Mon),
                  receive
                      {'DOWN', Mon , process, Pid, _} -> ok
                  %% We were previously guaranteed to get a down message
                  %% (since we exited the process ourself), so we could
                  %% in this case leave out:
                  %% after 0 -> ok
                  end,

  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-5772
- Two bugs fixed: If the environment variable ERL_FLAGS was set, its contents would be appended to the end of the command line even if the command line had an -extra options. Changed to place the options from ERL_FLAGS just before -extra. Also, the -smp and -hybrid flags no longer have any effect if placed after -extra.
  Own Id: OTP-6054

#### 1.20.2 Improvements and New Features

- The documentation for writing drivers in the ERTS User's Guide has been expanded and updated.
  Own Id: OTP-5192
- The andalso and orelse operators are now allowed to be used in guards. That also applies to match specifications.
  Own Id: OTP-5894 Aux Id: OTP-5149
- There is a new trace match spec function {exception_trace} and a corresponding trace message exception_from that can be used to trace on any exit from a function, both normal function return and exception return. See the documentation for details.
  The return_to trace message is now also generated when the execution returns to a function due to catching an exception.
  Own Id: OTP-5956
- Erlang runtime system with SMP (symmetric multi processing) support.
  The runtime system with SMP support is in this release focused on stability and there are a number of steps with optimizations to follow before it will take full advantage of multi processor systems. The released system is however thruly multi threaded and you will notice increased performance for many applications already. We recommend that you evaluate your application on the SMP version of the runtime system and wait for some more optimizations before you use it in a real product. You will then discover if there are any problems in your application that needs to be fixed in order for it to work properly in a multi threaded environment. More optimized versions of the runtime system with SMP support will be included in the R11B maintenance releases.
  The SMP enabled runtime system will be started if the -smp command line argument is passed to the erl command. In order to make use of more than one processor core, multiple scheduler threads are used. By default, the number of scheduler threads will equal the number of processor cores. The number of scheduler threads can be set with the +S command line argument. For more information see the erl(1) man page.
  A runtime system with SMP support is by default built on the following platforms if posix threads, and a gcc compiler of at least version 2.95 is found:
  - Linux with at least kernel version 2.6 and the Native POSIX Thread Library on x86, x86_64, and 32-bits PowerPC.
  - Solaris of at least version 8 on 32-bits SPARC-V9.
  - MacOSX of at least version 10.4 (Darwin 8.0) on 32-bits PowerPC.
  The runtime system with SMP support is known not to build on:
  - Windows.
  - Linux with kernel versions less than 2.4, or without the Native POSIX Thread Library.
  - Other hardware platforms than x86, x86_64, 32-bits SPARC-V9 and 32-bits PowerPC.
  Windows will be supported in a future release.
  The runtime system with SMP support might build on other operating systems in combination with supported hardware. In order to force a build of a runtime system with SMP support, pass the --enable-smp-support command line argument to configure. Note, however, that it is not enough that it builds. The underlying thread library and operating system has to provide SMP support as well. If the thread library does not distribute scheduler threads over multiple processor cores then the runtime system will only seemingly provide SMP support. If the runtime system is not built by default on a specific platform, we have not tested it on that platform.
  NOTE: The design of SMP support for drivers is ongoing. There will probably be incompatible driver changes (only affecting drivers run on the runtime system with SMP support) released as patches for R11B.
  Potential incompatibility: Previously, specific driver call-backs were always called from the same thread. This is not true in the runtime system with SMP support. Calls to call-backs will be made from different threads, e.g., two consecutive calls to exactly the same call-back can be made from two different threads. This will in most cases not be a problem. All calls to call-backs are synchronized, i.e., only one call-back will be called at a time.
  In the future the default behavior will probably be the following: Calls to call-backs will, as now, be made from different threads. Calls to call-backs in the same driver instance will be synchronized. It will probably be possible to configure so that all calls to call-backs in all driver instances of a specific driver type will be synchronized. It may be possible to configure so that all calls to call-backs of a driver instance or a of a specific driver type will be made from the same thread.
  Parallelism in the Erlang code executed is a necessity for the Erlang runtime system to be able to take advantage of multi-core or multi-processor hardware. There need to be at least as many Erlang processes runnable as processor cores for the Erlang runtime system to be able to take advantage of all processor cores.
  An Erlang runtime system with SMP support with only one Erlang process runnable all the time will almost always be slower than the same Erlang runtime system without SMP support. This is due to thread synchronization overhead.
  Known major bottleneck in the Erlang runtime system:
  - Currently the I/O system uses one "big lock", i.e. only one thread can do I/O at a time (with the exception of async threads and threads created by users own linked-in drivers). This is high on the list of things to optimize. Note, code that does not do I/O can be executed at the same time as one thread does I/O.
  Some pitfalls which might cause Erlang programs that work on the non-SMP runtime system to fail on the SMP runtime system:
  - A newly spawned process will often begin executing immediately. Code that expects that the parent process will be able to execute for a while before the child process begins executing is likely to fail.
  - High priority processes could previously provide mutual exclusion (bad programming style) by preventing normal and low priority processes from being run. High priority processes cannot be used this way to provide mutual exclusion.
  - erlang:yield() could be used to provide some kind of temporary mutual exclusion (also bad programming style). erlang:yield() cannot be used to provide any kind of mutual exclusion.
  - Obscure pitfall, only if a process being traced also sends normal messages to the tracer:
    The order between trace messages and normal messages is undefined. I.e. the order between normal messages sent from a tracee to a tracer and the trace messages generated from the same tracee to the same tracer is undefined. The internal order of normal messages and the internal order of trace messages will, of course, be preserved as before.
  The kernel poll feature is currently not supported by the runtime system with SMP support. It will probably be supported in a future release.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6006 Aux Id: OTP-6095
- Linked-in driver modifications.
  - Linked-in drivers must be recompiled.
  - The refc field in the ErlDrvBinary type has been removed. The reference count can be accessed via API functions. For more information see the erl_driver(1) man page.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-6095 Aux Id: OTP-6006

### 1.21 ERTS 5.4.13

#### 1.21.1 Fixed Bugs and Malfunctions

- Large files (more than 2 GBytes) are now handled on Solaris 8.
  Own Id: OTP-5849 Aux Id: seq10157
- A failing bit syntax construction could fail with the PREVIOUS exeption reason that had occured in the process (instead of with badarg).
  Own Id: OTP-5911
- When building OTP, the Kernel application was built in both the primary and secondary bootstrap steps, which would cause problems if OTP including its bootstrap is checked into a version control system (such as CVS). (Thanks to Sebastian Strollo.)
  Own Id: OTP-5921
- binary_to_term(<<131,109,255,255,255,255) and similar expressions used to crash the emulator instead of causing a badarg exception. (Thanks to Matthias Lang.)
  Own Id: OTP-5933
- erlang:hibernate/3 could sometimes crash the emulator when no heap was needed.
  Own Id: OTP-5940
- Execution of match specs could under rare circumstances cause the emulator to dump core.
  Execution of match specs could cause memory leaks in the hybrid emulator.
  Own Id: OTP-5955
- A bug in erlang:trace_info/2 when getting info for a function in a deleted module resulting in an emulator crash, has been corrected.
  Own Id: OTP-5957
- Different (and old) config.guess files in the ERTS and Erl_Interface applications would cause build problems on the new Intel-based iMacs. (Thanks to Sebastion Strollo.)
  Own Id: OTP-5967
- pthread header and library mismatch on Linux systems (at least some SuSE and Debian) with both NPTL and Linuxthreads libraries installed.
  Own Id: OTP-5981

#### 1.21.2 Improvements and New Features

- The driver_set_timer did not change the previous timeout if called a second time. Now it works as specified, changing the timeout.
  Own Id: OTP-5942
- The undocumented {packet,http} option (for the gen_tcp module) did not not work correctly when there were multiple continuation lines. (Thanks to Per Hedeland.)
  Own Id: OTP-5945
- The setuid_socket_wrap program was corrected to work for C compilers that treat the char type as unsigned. (Thanks to Magnus Henoch.)
  Own Id: OTP-5946

### 1.22 ERTS 5.4.12

#### 1.22.1 Fixed Bugs and Malfunctions

- Fixed a minor build problem on Windows.
  Own Id: OTP-5819 Aux Id: OTP-5382 OTP-5540 OTP-5577
- The delay_send option for gen_tcp was broken on Windows.
  Own Id: OTP-5822
- If there were user-defined variables in the boot script, and their values were not provided using the -boot_var option, the emulator would refuse to start with a confusing error message. Corrected to show a clear, understandable message.
  The prim_file module was modified to not depend on the lists module, to make it possible to start the emulator using a user-defined loader. (Thanks to Martin Bjorklund.)
  Own Id: OTP-5828 Aux Id: seq10151

#### 1.22.2 Improvements and New Features

- The HiPE compiler identifies more leaf functions, giving slightly faster code.
  Corrected problems in HiPE's coalescing register allocating that would cause it to fail when compiling very large functions (e.g. some of parse modules in the Megaco application).
  Own Id: OTP-5853

### 1.23 ERTS 5.4.11

#### 1.23.1 Fixed Bugs and Malfunctions

- Timers could sometimes timeout too early. This bug has now been fixed.
  Automatic cancellation of timers created by erlang:send_after(Time,pid(),Msg) and erlang:start_timer(Time,pid(),Msg) has been introduced. Timers created with the receiver specified by a pid, will automatically be cancelled when the receiver exits. For more information see the erlang(3) man page.
  In order to be able to maintain a larger amount of timers without increasing the maintenance cost, the internal timer wheel and bif timer table have been enlarged.
  Also a number of minor bif timer optimizations have been implemented.
  Own Id: OTP-5795 Aux Id: OTP-5090, seq8913, seq10139, OTP-5782
- erlang:monitor(process,Pid) hanged if Pid referred to a process on a non-existing node with the same nodename as the nodename of node on which the call was made. This bug has now been fixed.
  Own Id: OTP-5827

#### 1.23.2 Improvements and New Features

- By setting Unix environment variables, the priority for the emulator can be lowered when it is writing crash dumps and the time allowed for finishing writing a crash dump can be set to a certain number of seconds. See the documentation for erl in the ERTS application. (Also, a few other previously undocumented environment variables are now documented.)
  Own Id: OTP-5818
- Documentation improvements:
  - documentation for erlang:link/1 corrected
  - command line flag -code_path_cache added
  - erl command line flags clarifications
  - net_kernel(3) clarifications
  Own Id: OTP-5847

### 1.24 ERTS 5.4.10

#### 1.24.1 Fixed Bugs and Malfunctions

- -D_GNU_SOURCE is now always passed on the compile command line on linux. This in order to ensure that all included system headers see _GNU_SOURCE defined.
  _GNU_SOURCE is now also defined on linux in configure when looking for features.
  Some minor (harmless) configure bugs were also fixed.
  Own Id: OTP-5749
- Some compiler warnings and Dialyzer warnings were eliminated in the Tools application.
  When tracing to a port (which fprof does), there could be fake schedule out/schedule in messages sent for a process that had exited.
  Own Id: OTP-5757

#### 1.24.2 Improvements and New Features

- The BIFs iolist_size/1 and iolist_to_binary/1 has been added.
  The BIF list_to_existing_atom/1 has been added.
  Minor bug fix: The exception reason could be changed to error inside nested try/catch constructs if the erlang:raise/3 BIF was called with an empty stacktrace. (Calling erlang:raise/3 with an empty stacktrace is NOT recommended.)
  Minor bugfix: On Windows, file:open/2 will now return the documented error reason {error,eisdir} if the filename refers to a directory (it used to return {error,eacces}).
  The message in the documentation for erlang:system_monitor/2, description of busy_dist_port, was corrected.
  Own Id: OTP-5709 Aux Id: seq10100
- The previously undocumented and UNSUPPORTED zlib module has been updated in an incompatible way and many bugs have been corrected. It is now also documented.
  *** POTENTIAL INCOMPATIBILITY ***
  Own Id: OTP-5715
- New socket options priority and tos for platforms that support them (currently only Linux).
  Own Id: OTP-5756
- Only the emulator is now linked with termcap library in order to decrease library dependencies for other otp programs.
  Own Id: OTP-5758

### 1.25 ERTS 5.4.9.2

#### 1.25.1 Fixed Bugs and Malfunctions

- The native resolver has gotten an control API for extended debugging and soft restart. It is: inet_gethost_native:control(Control)
  Control = {debug_level,Level} | soft_restart
  Level = integer() in the range 0-4.
  Own Id: OTP-5751 Aux Id: EABln25013

### 1.26 ERTS 5.4.9.1

#### 1.26.1 Improvements and New Features

- On VxWorks, epmd did not handle file descriptors with higher numbers than 63. Also, if epmd should get a file descriptor with a number >= FD_SETSIZE, it will close a the file descritport and write a message to the log (instead of mysteriously fail); the Erlang node that tried to register will fail with a duplicate_name error (unfortunately, epmd has no way to indicate to the Erlang node why the register attempt failed).
  Own Id: OTP-5716 Aux Id: seq10070

### 1.27 ERTS 5.4.9

#### 1.27.1 Fixed Bugs and Malfunctions

- Timezone data is now initialized better. (was a problem at least on NetBSD 2.0.2) Thanks to Rich Neswold.
  Own Id: OTP-5621
- The hybrid-heap emulator ('erl -hybrid') is much more stable. We have corrected all known bugs that caused it to dump core while running our test suites.
  Own Id: OTP-5634
- Fixed rare memory leaks in erlang:demonitor/1 when distributed monitors were removed.
  Own Id: OTP-5692
- Processes were sometimes unnecessarily garbage collected when terminating. These unnecessary garbage collections have now been eliminated.
  Own Id: OTP-5693

#### 1.27.2 Improvements and New Features

- The c:i/0 function will now run in a paged mode if there are more than 100 processes in the system. (Thanks to Ulf Wiger.)
  erlang:system_info(process_count) has been optimized and does now return exactly the same value as length(processes()). Previously erlang:system_info(process_count) did not include exiting processes which are included in length(processes()).
  The +P flag for erl, which sets the maximum number of processes allowed to exist at the same, no longer accepts values higher than 134217727. (You will still probably run out of memory before you'll be able to reach that limit.)
  Own Id: OTP-5645 Aux Id: seq9984
- The term-building driver functions driver_output_term() and driver_send_term() have been updated:
  The ERL_DRV_FLOAT type has been added.
  For the ERL_DRV_BINARY type, the length and offset are now validated against the length of the driver binary.
  The ERL_DRV_PID type is now implemented (it was documented, but not implemented).
  Own Id: OTP-5674

### 1.28 ERTS 5.4.8

#### 1.28.1 Fixed Bugs and Malfunctions

- ets:delete/1 now allows other Erlang process to run when a large table is being deleted.
  Own Id: OTP-5572
- A bug regarding tcp sockets which results in hanging gen_tcp:send/2 has been corrected. To encounter this bug you needed one process that read from a socket, one that wrote more date than the reader read out so the sender got suspended, and then the reader closed the socket. (Reported and diagnosed by Alexey Shchepin.)
  Corrected a bug in the (undocumented and unsupported) option {packet,http} for gen_tcp. (Thanks to Claes Wikstrom and Luke Gorrie.)
  Updated the documentation regarding the second argument to gen_tcp:recv/2, the Length to receive.
  Own Id: OTP-5582 Aux Id: seq9839
- Erlang/OTP will now build on Mac OS X 10.4 "Tiger" (the problem was that 10.4 has a partially implemented poll() function that can't handle devices). Also, on Mac OS X 10.3 "Panther", Erlang/OTP will now use select() instead of poll() (because poll() on Mac OS X 10.3 is implemented using select()).
  Own Id: OTP-5595
- A bug in the file driver when opening a file in compressed mode, and the returned allocated pointer from the compressing library was in very high memory (>= 2GB), causing e.g. file:read/2 to return {error,ebadf}, has been corrected.
  Own Id: OTP-5618

#### 1.28.2 Improvements and New Features

- The new fun M:F/A construct creates a fun that refers to the latest version of M:F/A. This syntax is meant to replace tuple funs {M,F} which have many problems.
  The new type test is_function(Fun,A) (which may be used in guards) test whether Fun is a fun that can be applied with A arguments. (Currently, Fun can also be a tuple fun.)
  Own Id: OTP-5584
- In the HiPE application, there's a new experimental register allocator (optimistic coalescing), and the linear scan register allocator is now also available on ppc. Plus lots of cleanups.
  Minor hybrid heap corrections.
  The maximum size of a heap used to be articially limited so that the size of a heap would fit in 28 bits; that limitation could cause the emulator to terminate in a garbage collection even if there still was available memory. Now the largest heap size for a 32 bit CPU is 1,699,221,830 bytes. (Thanks to Jesper Wilhelmsson.)
  Also removed the undocumented +H emulator option.
  Own Id: OTP-5596

### 1.29 ERTS 5.4.7

#### 1.29.1 Fixed Bugs and Malfunctions

- to_erl could close unexpectedly on Linux systems. Also, output from the emulator could be lost. Corrected.
  Own Id: OTP-5561

#### 1.29.2 Improvements and New Features

- The cpu_timestamp option for erlang:trace/3 is now also supported on Linux.
  Own Id: OTP-5532 Aux Id: seq9813
- The last known werl window size/position is now saved correctly when werl is stopped with the window minimized. A problem with the placement not being saved if the emulator is halted or stopped from the JCL menu has also been fixed.
  Own Id: OTP-5544 Aux Id: OTP-5522

### 1.30 ERTS 5.4.6

#### 1.30.1 Fixed Bugs and Malfunctions

- Some math libraries do not always throw floating-point exceptions on errors. In order to be able to use these libraries, floating-point errors are now more thoroughly checked.
  Misc floating-point fixes for Linux and MacOSX.
  Own Id: OTP-5467
- An internal buffer was sometimes not cleared which caused garbage to appear in error messages sent to the error logger.
  errno was sometimes clobbered which caused erroneous error reports about poll() errors.
  Only emulators on unix platforms were affected by these bugs.
  Own Id: OTP-5492
- The ethread library now works on OpenBSD.
  Own Id: OTP-5515
- Corrected a bug in the (undocumented and unsupported) option {packet,http} for gen_tcp. (Thanks to Claes Wikstrom and Luke Gorrie.)
  Own Id: OTP-5519

#### 1.30.2 Improvements and New Features

- binary_to_term/1 could cause the emulator to crash when given invalid pids or funs.
  Own Id: OTP-5484 Aux Id: seq9801
- Some more stability problems were fixed in the hybrid-heap emulator.
  Own Id: OTP-5489
- After werl was closed with the window minimized, it was not possible to restart werl with an open window. A temporary solution has so far been implemented that restores the initial window settings every time werl is started.
  Own Id: OTP-5522

### 1.31 ERTS 5.4.5

#### 1.31.1 Fixed Bugs and Malfunctions

- If a process had node links (created by monitor_node/2), excuting process_info(Pid,memory) for that process would crash the emulator.
  Own Id: OTP-5420
- Minor corrections to the help text printed by erlc -help. The documentation for erlc was also slightly updated.
  Own Id: OTP-5428
- 32-bit words were used for offsets in the garbage collector. This caused the emulator to crash on 64-bit machines when heaps were moved more than 4 GB during garbage collection.
  Own Id: OTP-5430
- is_boolean(42.5) failed to load if optimization was explicitly turned off.
  Own Id: OTP-5448
- If there was a call to Module:foo/X from any loaded module, the returned by M:module_info(exports) would always include {foo,X} (even though Module:foo/X if was not defined).
  Own Id: OTP-5450 Aux Id: seq9722

#### 1.31.2 Improvements and New Features

- The c option for the +B flag has been introduced which makes it possible to use Ctrl-C (Ctrl-Break on Windows) to interrupt the shell process rather than to invoke the emulator break handler. All new +B options are also supported on Windows (werl) as of now. Furthermore, Ctrl-C on Windows has now been reserved for copying text (what Ctrl-Ins was used for previously). Ctrl-Break should be used for break handling. Lastly, the documentation of the system flags has been updated.
  Own Id: OTP-5388

### 1.32 ERTS 5.4.4

#### 1.32.1 Fixed Bugs and Malfunctions

- The function erlang:float/1 can now be used in match specifications and is recognized by dbg:fun2ms/1 and ets:fun2ms/1. This addition is part of the work to "harmonize" match specification guards with Erlang guards.
  Own Id: OTP-5297 Aux Id: OTP-4927
- The register/2 BIF would return true even if the second argument was not a pid for living process. Corrected to cause an exception.
  Own Id: OTP-5324 Aux Id: seq9698
- In the 'bag' type of ets tables, elements having the same key were supposed to be order in insertion order. The would be wrong if a rehash occurred.
  Own Id: OTP-5340 Aux Id: seq9704
- Linked in drivers in the Crypto and Asn1 applications are now compiled with the -D_THREAD_SAFE and -D_REENTRANT switches on unix when the emulator has thread support enabled.
  Linked in drivers on MacOSX are not compiled with the undocumented -lbundle1.o switch anymore. Thanks to Sean Hinde who sent us a patch.
  Linked in driver in Crypto, and port programs in SSL, now compiles on OSF1.
  Minor makefile improvements in Runtime_Tools.
  Own Id: OTP-5346
- Fixed a bug in the hybrid heap in distributed send operations.
  Own Id: OTP-5361
- A BIF erlang:raise/3 has been added. See the manual for details. It is intended for internal system programming only, advanced error handling.
  Own Id: OTP-5376 Aux Id: OTP-5257
- Mikael Pettersson (HiPE) corrected a few bugs in the emulator that caused problems when compiled with the experimental gcc-4.0.0.
  Own Id: OTP-5386

#### 1.32.2 Improvements and New Features

- Minor update of the internal documentation of the epmd protocol.
  The listen port of epmd has now been registered at IANA: http://www.iana.org/assignments/port-numbers.
  Own Id: OTP-5234
- run_erl.c now works on Mac OS X and FreeBSD.
  Own Id: OTP-5384
- A few bugs were corrected in the HiPE application.
  Own Id: OTP-5385

### 1.33 ERTS 5.4.3

#### 1.33.1 Fixed Bugs and Malfunctions

- Font and color preferences for werl.exe now can be saved even after the first time you run werl.exe. The window position and size is also saved. Patch from James Hague who did all the hard work.
  Own Id: OTP-5250
- OTP archive libraries, e.g. the erl_interface library, on MacOSX could not be used without first rerunning ranlib on them. This bug has now been fixed.
  Own Id: OTP-5274
- Bugs in erlang:hash/2 and erlang:phash/2 on 64-bit platforms have been fixed.
  Own Id: OTP-5292

#### 1.33.2 Improvements and New Features

- Corrected a crash in the 64-bits emulator.
  Corrected a problem in the hybrid heap emulator.
  In the chapter about the abstract format in the ERTS User's Guide, updated the last section about how the abstract format is stored in BEAM files.
  Own Id: OTP-5262
- The maximum number of concurrent threads in the internal ethread thread package has been limited to 2048.
  Own Id: OTP-5280

### 1.34 ERTS 5.4.2.1

#### 1.34.1 Improvements and New Features

- If Erlang/OTP was installed in a short directory name, such as C:\Program\erl5.4.2, the emulator would not start.
  Own Id: OTP-5254

### 1.35 ERTS 5.4.2

#### 1.35.1 Fixed Bugs and Malfunctions

- If one used select/3 and select/1 on a non-fixed ETS table and deleted objects simultaneously, the emulator could crash. Note that the result of such simultaneous operations on tables that are not in a fixed state is still undefined, but the emulator crash is, needless to say, fixed.
  Own Id: OTP-5209 Aux Id: seq9198
- Arithmetic with big numbers could crash the emulator.
  The HiPE native code compiler and run-time code in the emulator has been updated. (Note: Native code is still not supported.)
  Eliminated a few bugs that could crash the hybrid emulator (which is not supported).
  Own Id: OTP-5233 Aux Id: seq9587

### 1.36 ERTS 5.4.1

#### 1.36.1 Fixed Bugs and Malfunctions

- The ethread library was unnecessarily rebuilt multiple times during the build process, also a debug version of the library was build during the install phase. These unnecessary builds have now been removed. Note, the content of the installed Erlang/OTP system is not effected at all by this change.
  Own Id: OTP-5203
- The emulator could fail to clear the memory segment cache. This could potentially cause memory allocation to unnecessarily fail when memory usage was close to its maximum. This bug has now been fixed.
  Own Id: OTP-5211
- std_alloc (std short for standard) was sometimes called def_alloc (def short for default). std_alloc is now everywhere refered to as std_alloc.
  Own Id: OTP-5216
- A documentation bug has been corrected in the erts_alloc(3) documentation. It was stated that some of the memory allocators present were by default disabled. This is true for Erlang/OTP R9C, but is not true for Erlang/OTP R10B. In R10B all memory allocators present are enabled by default.
  Own Id: OTP-5217

#### 1.36.2 Improvements and New Features

- The emulator now close all open files and sockets immediately after receiving an USR1 signal. This causes the emulator to unregister at epmd as early as possible.
  Own Id: OTP-5221 Aux Id: OTP-4985, seq9514
- Try/catch support in the emulator slightly updated.
  Own Id: OTP-5229

erts 5.6.1
Copyright © 1991-2008 Ericsson AB