<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2004</year><year>2013</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>Compiler Release Notes</title>
<prepared>otp_appnotes</prepared>
<docno>nil</docno>
<date>nil</date>
<rev>nil</rev>
<file>notes.xml</file>
</header>
<p>This document describes the changes made to the Compiler
application.</p>
<section><title>Compiler 6.0.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Fix <c>get_map_elements</c> register corruption</p>
<p>
Instruction <c>get_map_elements</c> might destroy target
registers when the fail-label is taken. Only seen for
patterns with two, and only two, target registers.
Specifically if we copy one register and then jump.</p>
<p>
Own Id: OTP-12967</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 6.0</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
The compiler optimizes away building of terms that are
never actually used. As a result, the compiler in OTP 18
may produce more warnings for terms that are built but
not used than the compiler in OTP 17.</p>
<p>
Own Id: OTP-12453</p>
</item>
<item>
<p>
Using a map could incorrectly suppress warnings for
unused variables.</p>
<p>
Own Id: OTP-12515</p>
</item>
<item>
<p>
The compiler now properly reports unknown parse
transforms. That is, <c>undef</c> exceptions coming from
the parse transform itself is reported differently from
the absence of the parse transform.</p>
<p>
Own Id: OTP-12723</p>
</item>
<item>
<p>
Allow for 'creation of sub binary delayed' optimization
if maps instructions are in a clause.</p>
<p>
Own Id: OTP-12758</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The <c>cerl</c> and <c>cerl_trees</c> modules in the
<c>compiler</c> application are now documented.</p>
<p>
Own Id: OTP-11978</p>
</item>
<item>
<p>
The deprecated '<c>asm</c>' option has been removed.</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-12100</p>
</item>
<item>
<p>
Support variables as Map keys in expressions and patterns</p>
<p>Erlang will accept any expression as keys in Map
expressions and it will accept literals or bound
variables as keys in Map patterns.</p>
<p>
Own Id: OTP-12218</p>
</item>
<item>
<p>
Infer Map type information in beam_type compiler
optimization pass.</p>
<p>
Own Id: OTP-12253</p>
</item>
<item>
<p>
Compiler optimizations have been improved.</p>
<p>
Own Id: OTP-12393</p>
</item>
<item>
<p>
Five undocumented functions in the module <c>core_lib</c>
have been deprecated and will be removed in the next
major release. The functions are: <c>get_anno/{1,2}</c>,
<c>is_literal/1</c>, <c>is_literal_list/1</c>, and
<c>literal_value</c>. Use the appropriate functions in
the <c>cerl</c> module instead.</p>
<p>
Own Id: OTP-12497</p>
</item>
<item>
<p>
Change some internal data structures to Maps in order to
speed up compilation time. Measured speed up is around
10%-15%.</p>
<p>
Own Id: OTP-12774</p>
</item>
<item>
<p>
Fix beam_bool pass for Maps instruction get_map_elements</p>
<p>
Before beam_split the get_map_elements instruction is
still in blocks and the helper function in beam_jump did
not reflect this.</p>
<p>
Own Id: OTP-12844 Aux Id: 17 </p>
</item>
</list>
</section>
</section>
<section><title>Compiler 5.0.4</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Matching out a map from a record and then updating the
record could cause a 'badarg' exception at run-time.
(Thanks to Dmitry Aleksandrov for reporting this bug.)</p>
<p>
Own Id: OTP-12402</p>
</item>
<item>
<p>The compiler would crash when compiling some complex,
nonsensical guards such as:</p>
<p> ... <c>when {{X}}, -X</c>...</p>
<p>
Own Id: OTP-12410</p>
</item>
<item>
<p>
In rare circumstances, using binary pattern in the value
part of a map pattern would cause the compiler to crash.</p>
<p>
Own Id: OTP-12414</p>
</item>
<item>
<p>Case expressions where a map was wrapped in a tuple or
list such as:</p>
<p><c>case {a,Map} of</c><br/> <c>{a,#{k:=_}}=Tuple ->
Tuple</c><br/> <c>end.</c></p>
<p>would be unsafely "optimized" to either cause an
exception at run-time or would return an empty map.</p>
<p>
Own Id: OTP-12451</p>
</item>
<item>
<p>When a variable was compared to a literal map using
the '<c>==</c>' operator, the compiler would change the
operator to '<c>=:=</c>' since it is more efficient.
However, this optimization is not safe if the map literal
has numeric keys or values. The compiler will now only do
the optimization if all keys and values are
non-numeric.</p>
<p>
Own Id: OTP-12456</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 5.0.3</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Named funs with the same name and arity could get mixed
up with each other.</p>
<p>
Own Id: OTP-12262</p>
</item>
<item>
<p>
Coalesce map keys in dialyzer mode</p>
<p>
This fixes a regression introduced in commit
805f9c89fc01220bc1bb0f27e1b68fd4eca688ba The problem
occurred with compounded map keys compiled with dialyzer
option turned on, '+dialyzer'.</p>
<p>
Reported by: Ivan Uemlianin</p>
<p>
Own Id: OTP-12347</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 5.0.2</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Corrected a bug with incorrect code generation when
inlining was turned on.</p>
<p>
Own Id: OTP-12132</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 5.0.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
A Dialyzer crash involving analysis of Map types has now
been fixed.</p>
<p>
Own Id: OTP-11947</p>
</item>
<item>
<p>The compiler would fail to compile a file with a
latin-1 character in the false branch of an <c>-ifdef</c>
or <c>-indef</c>.</p>
<p>
Own Id: OTP-11987</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 5.0</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Line numbers would not be correct when a binary
construction such as
'<c><<Bin/binary,...>></c>' fails. (Thanks to
Stanislav Seletskiy for reporting this bug.)</p>
<p>
Own Id: OTP-11572</p>
</item>
<item>
<p>
The compiler now properly annotates the code in value in
the '<c>after</c>' clause for a '<c>try</c>' so that
Dialyzer no longer generates a false warning for an
unmatched return.</p>
<p>
Own Id: OTP-11580</p>
</item>
<item>
<p>
Some case statements where no clause would match could
cause an internal error in the compiler. (Thanks to Erik
Soe Sorensen for reporting this bug.)</p>
<p>
Own Id: OTP-11610</p>
</item>
<item>
<p>
With <c>--Wunmatched_returns</c>, dialyzer will no longer
warn when the value of a list comprehension is ignored,
provided that the each value in the list would be an
atomic value (such as integer or atoms, as opposed to
tuples and lists). Example: ignoring '<c>[io:format(...)
|| ...]</c>' will not cause a warning, while ignoring
'<c>[file:close(Fd) || ...]</c>' will.</p>
<p>
Own Id: OTP-11626</p>
</item>
<item>
<p>
Matching out a binary and applying the binary as if it
were a fun would crash the run-time system. (Thanks to
Loïc Hoguin.)</p>
<p>
Own Id: OTP-11672</p>
</item>
<item>
<p>
Some local implementations of removing the last element
from a list are replaced by <c>lists:droplast/1</c>. Note
that this requires at least <c>stdlib-2.0</c>, which is
the stdlib version delivered in OTP 17.0. (Thanks to Hans
Svensson)</p>
<p>
Own Id: OTP-11678</p>
</item>
<item>
<p>
Allow all auto imports to be suppressed at once.
Introducing the no_auto_import attribute:
-compile(no_auto_import). Useful for code generation
tools that always use the qualified function names and
want to avoid the auto imported functions clashing with
local ones. (Thanks to José Valim.)</p>
<p>
Own Id: OTP-11682</p>
</item>
<item>
<p>
Application upgrade (appup) files are corrected for the
following applications: </p>
<p>
<c>asn1, common_test, compiler, crypto, debugger,
dialyzer, edoc, eldap, erl_docgen, et, eunit, gs, hipe,
inets, observer, odbc, os_mon, otp_mibs, parsetools,
percept, public_key, reltool, runtime_tools, ssh,
syntax_tools, test_server, tools, typer, webtool, wx,
xmerl</c></p>
<p>
A new test utility for testing appup files is added to
test_server. This is now used by most applications in
OTP.</p>
<p>
(Thanks to Tobias Schlager)</p>
<p>
Own Id: OTP-11744</p>
</item>
<item>
<p>
Adapt 'asm' deprecation message to new version scheme.
(Thanks to Tuncer Ayaz)</p>
<p>
Own Id: OTP-11751</p>
</item>
<item>
<p>
A number of compiler errors where unusual or nonsensical
code would crash the compiler have been reported by Ulf
Norell and corrected by Anthony Ramine.</p>
<p>
Own Id: OTP-11770</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Compilation times for modules with a huge number for
record accesses using the dot operator has been improved.</p>
<p>
Own Id: OTP-10652</p>
</item>
<item>
<p>
The compiler can generate somewhat better code by moving
let expressions into sequences. (Thanks to Anthony
Ramine.)</p>
<p>
Own Id: OTP-11056</p>
</item>
<item>
<p>
Forbid unsized fields in patterns of binary generators
and simplified v3_core's translation of bit string
generators. (Thanks to Anthony Ramine.)</p>
<p>
Own Id: OTP-11186</p>
</item>
<item>
<p>
Funs can now be a given a name. Thanks to to Richard
O'Keefe for the idea (EEP37) and to Anthony Ramine for
the implementation.</p>
<p>
Own Id: OTP-11537</p>
</item>
<item>
<p>
Using the <c>from_asm</c> option to produce a BEAM file
starting from BEAM assembly code would often fail because
early optimization passes would not understand
instructions that later optimization passes would
introduce. (Thanks to Anthony Ramine.)</p>
<p>
Own Id: OTP-11544</p>
</item>
<item>
<p>
The <c>.core</c> and <c>.S</c> extensions are now
documented in the <c>erlc</c> documentation, and the
'<c>from_core</c>' and '<c>from_asm</c>' options are now
documented in the compiler documentation. (Thanks to
Tuncer Ayaz.)</p>
<p>
Own Id: OTP-11547</p>
</item>
<item>
<p>Optimization of case expressions that build tuples or
lists have been improved.</p>
<p>
Own Id: OTP-11584</p>
</item>
<item>
<p>
EEP43: New data type - Maps</p>
<p>
With Maps you may for instance:</p>
<taglist>
<tag/> <item><c>M0 = #{ a => 1, b => 2}, % create
associations</c></item>
<tag/><item><c>M1 = M0#{ a := 10 }, % update values</c></item>
<tag/><item><c>M2 = M1#{ "hi" =>
"hello"}, % add new associations</c></item>
<tag/><item><c>#{ "hi" := V1, a := V2, b := V3} = M2.
% match keys with values</c></item>
</taglist>
<p>
For information on how to use Maps please see Map Expressions in the
<seealso marker="doc/reference_manual:expressions#map_expressions">
Reference Manual</seealso>.</p>
<p>
The current implementation is without the following
features:</p>
<taglist>
<tag/><item>No variable keys</item>
<tag/><item>No single value access</item>
<tag/><item>No map comprehensions</item>
</taglist>
<p>
Note that Maps is <em>experimental</em> during OTP 17.0.</p>
<p>
Own Id: OTP-11616</p>
</item>
<item>
<p>
Some function specs are corrected or moved and some edoc
comments are corrected in order to allow use of edoc.
(Thanks to Pierre Fenoll)</p>
<p>
Own Id: OTP-11702</p>
</item>
<item>
<p>
Thanks to Anthony Ramine for several improvements to the
optimizations in the BEAM compiler and for cleaning up
the code the code that transforms list and binary
comprehensions to Core Erlang.</p>
<p>
Own Id: OTP-11720</p>
</item>
<item>
<p>
The default encoding for Erlang source files is now
UTF-8. As a temporary measure to ease the transition from
the old default of latin-1, if the compiler encounters
byte sequences that are not valid UTF-8 sequences, the
compiler will re-try the compilation in latin-1 mode.
This workaround will be removed in a future release.</p>
<p>
Own Id: OTP-11791</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.9.4</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Typo fix ambigous -> ambiguous. Thanks to Leo Correa.</p>
<p>
Own Id: OTP-11455</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Lift 'after' blocks to zeroary functions. Thanks to
Anthony Ramine.</p>
<p>
Own Id: OTP-11267</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.9.3</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Expressions such as <c>'B = is_integer(V), if B and B
-> ok end'</c> would crash the compiler.</p>
<p>
Own Id: OTP-11240</p>
</item>
<item>
<p>
<c>compile:file2/2</c> with the option
<c>report_errors</c> could return ErrorInfo tuples with
only two elements, while the documentation says that the
ErrorInfo tuple always has three elements. Also updated
the documentation to add that the first element may be
'<c>none</c>' if no line number is applicable.</p>
<p>
Own Id: OTP-11304 Aux Id: seq12412 </p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Fix matching of floating point middle-endian machines.
Thanks to Johannes Weissl.</p>
<p>
Own Id: OTP-11201</p>
</item>
<item>
<p>
Restrict inlining of local fun references. Thanks to
Anthony Ramine.</p>
<p>
Own Id: OTP-11211</p>
</item>
<item>
<p>
Silence a misleading warning with some comprehensions.
Thanks to Anthony Ramine.</p>
<p>
Own Id: OTP-11212</p>
</item>
<item>
<p>
Forbid returning a match context in beam_validator.
Thanks to Anthony Ramine.</p>
<p>
Own Id: OTP-11247</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.9.2</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Compiling functions with complex boolean operations in
guards could be very slow. (Thanks to Magnus Muller for
reporting this issue.)</p>
<p>
Own Id: OTP-10939</p>
</item>
<item>
<p>
Certain guard expressions used in a receive statement
could cause the compiler to crash.</p>
<p>
Own Id: OTP-11119 Aux Id: seq12342 </p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Fix optimization of some binary comprehensions. Thanks to
Anthony Ramine.</p>
<p>
Own Id: OTP-11005</p>
</item>
<item>
<p>
Use a set to store ref registers in beam_receive. Thanks
to Anthony Ramine.</p>
<p>
Own Id: OTP-11069</p>
</item>
<item>
<p>
Fix renaming of bs_put_string instructions. Thanks to
Anthony Ramine.</p>
<p>
Own Id: OTP-11129</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.9.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
The compiler would crash attempting to compile
expressions such as "element(2, not_tuple)".</p>
<p>
Own Id: OTP-10794</p>
</item>
<item>
<p>
Forbid multiple values in Core Erlang sequence arguments.
Thanks to José Valim and Anthony Ramine.</p>
<p>
Own Id: OTP-10818</p>
</item>
<item>
<p>
An unsafe optimization would cause the compiler to crash
with an internal error for certain complex code
sequences.</p>
<p>
Own Id: OTP-10825 Aux Id: seq12247 </p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>Integers in expression that will give a floating point
result (such as "<c>X / 2</c>" will now be converted to
floating point at compile-time. (Suggested by Richard
O'Keefe.)</p>
<p>Identical floating points constans in a module will
now be coalesced to one entry in the constant pool.</p>
<p>
Own Id: OTP-10788</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.9</title>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The compiler optimizations have been polished, so that
the code quality will be slightly better in some cases.</p>
<p>
Own Id: OTP-10193</p>
</item>
<item>
<p> Support for Unicode has been implemented. </p>
<p>
Own Id: OTP-10302</p>
</item>
<item>
<p>Where necessary a comment stating encoding has been
added to Erlang files. The comment is meant to be removed
in Erlang/OTP R17B when UTF-8 becomes the default
encoding. </p>
<p>
Own Id: OTP-10630</p>
</item>
<item>
<p>
Fix some wrong warnings triggered by the option
inline_list_funcs. Thanks to Anthony Ramine.</p>
<p>
Own Id: OTP-10690</p>
</item>
<item>
<p>
Forbid local fun variables in Core Erlang guards. Thanks
to Anthony Ramine.</p>
<p>
Own Id: OTP-10706</p>
</item>
<item>
<p>
Binary syntax matches could cause an internal consistency
error in in the compiler. (Thanks to Viktor Sovietov for
reporting this bug.)</p>
<p>
Own Id: OTP-10724</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.8.2</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Modules with very many functions would compile very
slowly.</p>
<p>
Own Id: OTP-10123</p>
</item>
<item>
<p>
<c>compile:forms/2</c> will now use a
{source,SourceFilePath} to set the source returned by
<c>module_info(compile)</c> (Thanks to José Valim)</p>
<p>
Own Id: OTP-10150</p>
</item>
<item>
<p>
A process which had enabled trap_exit would receive EXIT
messages after calling the compiler. (Thanks to Jeremy
Heater.)</p>
<p>
Own Id: OTP-10171</p>
</item>
<item>
<p>
Fix messages ordering with column numbers</p>
<p>
Own Id: OTP-10183</p>
</item>
<item>
<p>
sys_pre_expand: Fix BASE never being set</p>
<p>
Commit a612e99fb5aaa934fe5a8591db0f083d7fa0b20a turned
module attributes from 2-tuples to 3-tuples but forgot to
update get_base/1, breaking BASE for parametric modules.</p>
<p>
Own Id: OTP-10184</p>
</item>
<item>
<p>
The compiler will now issue a warning if literal tuple
funs are used. For example, {erlang,is_tuple}(X) will now
generate a warning.</p>
<p>
Own Id: OTP-10185</p>
</item>
<item>
<p>
The compiler will now warn for illegal sizes for segments
in binary construction. For example,
<<X:(2.5)>> will now cause the compiler to
issue a warning.</p>
<p>
Own Id: OTP-10197</p>
</item>
<item>
<p>
Fix the erlc -MP flag</p>
<p>
Because of a copy-and-paste error in erlc.c, the -MP flag
had the same effect as -MG. As a workaround, you had to
pass +makedep_phony to enable the MP option. This patch
makes -MP work as intended.</p>
<p>
Own Id: OTP-10211</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.8.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
In rare circumstance, the compiler could crash when
compiling a case statement. (Thanks to Hakan Mattsson.)</p>
<p>
Own Id: OTP-9842</p>
</item>
<item>
<p>Calling a guard test (such as is_list/1) from the
top-level in a guard, would cause a compiler crash if
there was a local definition with the same name.
Corrected to reject the program with an error
message.</p>
<p>
Own Id: OTP-9866</p>
</item>
<item>
<p>Using <c>get/1</c> in a <c>try</c> block could in some
cases cause an internal compiler error. (Thanks to Eric
Merritt.)</p>
<p>
Own Id: OTP-9867</p>
</item>
<item>
<p>
An unexported on_load function would not get run if the
module was compiled with the <c>inline</c> option.
(Thanks to Yiannis Tsiouris.)</p>
<p>
Own Id: OTP-9910</p>
</item>
<item>
<p>
Fixed a discrepancy in compile_info</p>
<p>
The BEAM disassembler used the atom 'none' to signify the
absence of a compile_info chunk in a .beam file. This
clashed with the type declaration of the compile_info
field of a #beam_file{} record as containing a list. Now
[] signifies the absence of this chunk. This simplifies
the code and avoids a dialyzer warning.</p>
<p>
Own Id: OTP-9917</p>
</item>
<item>
<p>
Fix typo in `compile' doc: unmatched parenthesis (Thanks
to Ricardo Catalinas Jiménez)</p>
<p>
Own Id: OTP-9919</p>
</item>
<item>
<p>In a <c>try</c>...<c>catch</c> statement that always
returned <c>false</c>, the compiler would remove calls to
BIFs that could not cause an exception (such as
<c>put/2</c>). Example of such code: <c>try put(K, V),
false catch _:_ -> false end.</c></p>
<p>
Own Id: OTP-9982</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.8</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Add '-callback' attributes in stdlib's behaviours</p>
<p>
Replace the behaviour_info(callbacks) export in stdlib's
behaviours with -callback' attributes for all the
callbacks. Update the documentation with information on
the callback attribute Automatically generate
'behaviour_info' function from '-callback' attributes</p>
<p>
'behaviour_info(callbacks)' is a special function that is
defined in a module which describes a behaviour and
returns a list of its callbacks.</p>
<p>
This function is now automatically generated using the
'-callback' specs. An error is returned by lint if user
defines both '-callback' attributes and the
behaviour_info/1 function. If no type info is needed for
a callback use a generic spec for it. Add '-callback'
attribute to language syntax</p>
<p>
Behaviours may define specs for their callbacks using the
familiar spec syntax, replacing the '-spec' keyword with
'-callback'. Simple lint checks are performed to ensure
that no callbacks are defined twice and all types
referred are declared.</p>
<p>
These attributes can be then used by tools to provide
documentation to the behaviour or find discrepancies in
the callback definitions in the callback module.</p>
<p>
Add callback specs into 'application' module in kernel
Add callback specs to tftp module following internet
documentation Add callback specs to inets_service module
following possibly deprecated comments</p>
<p>
Own Id: OTP-9621</p>
</item>
<item>
<p>
The calculation of the 'uniq' value for a fun (see
<c>erlang:fun_info/1</c>) was too weak and has been
strengthened. It used to be based on the only the code
for the fun body, but it is now based on the MD5 of the
BEAM code for the module.</p>
<p>
Own Id: OTP-9667</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>Variables are now now allowed in '<c>fun M:F/A</c>' as
suggested by Richard O'Keefe in EEP-23.</p>
<p>The representation of '<c>fun M:F/A</c>' in the
abstract format has been changed in an incompatible way.
Tools that directly read or manipulate the abstract
format (such as parse transforms) may need to be updated.
The compiler can handle both the new and the old format
(i.e. extracting the abstract format from a pre-R15 BEAM
file and compiling it using compile:forms/1,2 will work).
The <c>syntax_tools</c> application can also handle both
formats.</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-9643</p>
</item>
<item>
<p>
<c>filename:find_src/1,2</c> will now work on stripped
BEAM files (reported by Per Hedeland). The HiPE compiler
will also work on stripped BEAM files. The BEAM compiler
will no longer include compilation options given in the
source code itself in <c>M:module_info(compile)</c>
(because those options will be applied anyway if the
module is re-compiled).</p>
<p>
Own Id: OTP-9752</p>
</item>
<item>
<p>Inlining binary matching could cause an internal
compiler error. (Thanks to Rene Kijewski for reporting
this bug.)</p>
<p>
Own Id: OTP-9770</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.7.5</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Compiler options given in the source code using a
<c>-compile()</c> attribute used to be included twice in
<c>Mod:module_info(compile)</c>. They are now only
included once at the beginning of the list of options.</p>
<p>
Own Id: OTP-9534</p>
</item>
<item>
<p>
beam_disasm: Handle stripped BEAM files</p>
<p>
beam_disasm:file/1 would crash if asked to disassemble a
stripped BEAM file without an "Attr" chunk. (Thanks to
Haitao Li)</p>
<p>
Own Id: OTP-9571</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.7.4</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
If a variable is matched out in binary matching and used
as the size for a binary element, it would seem to be
unbound if used in a subsequent match operation. (Thanks
to Bernard Duggan.)</p>
<p>
Own Id: OTP-9134</p>
</item>
<item>
<p>Eliminate incorrect warning in
<c>sys_core_fold</c></p>
<p>
Own Id: OTP-9152</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.7.3</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
The <c>-export_type()</c> directive is no longer included
among the attributes.</p>
<p>
Own Id: OTP-8998</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The maximum number of allowed arguments for an Erlang
function has been lowered from 256 to 255, so that the
number of arguments can now fit in a byte.</p>
<p>
Own Id: OTP-9049</p>
</item>
<item>
<p>
Dependency generation for Makefiles has been added to the
compiler and erlc. See the manual pages for
<c>compile</c> and <c>erlc</c>. (Thanks to Jean-Sebastien
Pedron.)</p>
<p>
Own Id: OTP-9065</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.7.2</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Two compiler bugs (that would cause the compiler to
terminate) reported by Christopher Williams have been
fixed.</p>
<p>
Own Id: OTP-8949</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>The compiler would translate binary comprehensions
containing tail segments in a way that would would
confuse Dialyzer. For instance:</p>
<p><c>[42 || <<_:8/integer, _/bits>> <=
Bits]</c></p>
<p>
would produce a Dialyzer warning.</p>
<p>
Own Id: OTP-8864</p>
</item>
<item>
<p>
Code such as <c>foo(A) -> <<A:0>></c>
would crash the compiler.</p>
<p>
Own Id: OTP-8865</p>
</item>
<item>
<p>
The compiler could fail with an internal error when
variables were exported from a receive block but the
return value of the receive block were not used. (Thanks
to Jim Engquist for reporting this error.)</p>
<p>
Own Id: OTP-8888</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.7.1</title>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Eliminated warnings for auto-imported BIF clashes.</p>
<p>
Own Id: OTP-8840</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.7</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Several problems in the inliner have been fixed.</p>
<p>
Own Id: OTP-8552</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The module binary from EEP31 (and EEP9) is implemented.</p>
<p>
Own Id: OTP-8217</p>
</item>
<item>
<p>Local and imported functions now override the
auto-imported BIFs when the names clash. The pre R14
behaviour was that auto-imported BIFs would override
local functions. To avoid that old programs change
behaviour, the following will generate an error:</p>
<list><item><p>Doing a call without explicit module name
to a local function having a name clashing with the name
of an auto-imported BIF that was present (and
auto-imported) before OTP R14A</p></item>
<item><p>Explicitly importing a function having a name
clashing with the name of an autoimported BIF that was
present (and autoimported) before OTP R14A</p></item>
<item><p>Using any form of the old compiler directive
<c>nowarn_bif_clash</c></p></item> </list> <p>If the BIF
was added or auto-imported in OTP R14A or later,
overriding it with an import or a local function will
only result in a warning,</p> <p>To resolve clashes, you
can either use the explicit module name <c>erlang</c> to
call the BIF, or you can remove the auto-import of that
specific BIF by using the new compiler directive
<c>-compile({no_auto_import,[F/A]}).</c>, which makes all
calls to the local or imported function without explicit
module name pass without warnings or errors.</p> <p>The
change makes it possible to add auto-imported BIFs
without breaking or silently changing old code in the
future. However some current code ingeniously utilizing
the old behaviour or the <c>nowarn_bif_clash</c> compiler
directive, might need changing to be accepted by the
compiler.</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-8579</p>
</item>
<item>
<p>The undocumented, unsupport, and deprecated function
<c>lists:flat_length/1</c> has been removed.</p>
<p>
Own Id: OTP-8584</p>
</item>
<item>
<p>Nested records can now be accessed without
parenthesis. See the Reference Manual for examples.
(Thanks to YAMASHINA Hio and Tuncer Ayaz.)</p>
<p>
Own Id: OTP-8597</p>
</item>
<item>
<p>It is now possible to suppress the warning in code
such as "<c>list_to_integer(S), ok</c>" by assigning the
ignored value "_" like this: "<c>_ = list_to_integer(S),
ok</c>".</p>
<p>
Own Id: OTP-8602</p>
</item>
<item>
<p><c>receive</c> statements that can only read out a
newly created reference are now specially optimized so
that it will execute in constant time regardless of the
number of messages in the receive queue for the process.
That optimization will benefit calls to
<c>gen_server:call()</c>. (See <c>gen:do_call/4</c> for
an example of a receive statement that will be
optimized.)</p>
<p>
Own Id: OTP-8623</p>
</item>
<item>
<p>The compiler optimizes record operations better.</p>
<p>
Own Id: OTP-8668</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6.5</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Using complex boolean expressions in ifs could cause the
compiler to either crash or teminate with an internal
error. (Thanks to Simon Cornish.)</p>
<p>
Own Id: OTP-8338</p>
</item>
<item>
<p>Bit string comprehensions can now be used in
parameterized modules. (Thanks to Jebu Ittiachen.)</p>
<p>
Own Id: OTP-8447</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The expected return value for an on_load function has
been changed. (See the section about code loading in the
Reference manual.)</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-8339</p>
</item>
<item>
<p>
In rare circumstances when using garbaging collecting
guard BIFs, the validation pass (beam_validator) would
signal that the code was unsafe, when it in fact was
correct. (Thanks to Kiran Khaladkar.)</p>
<p>
Own Id: OTP-8378</p>
</item>
<item>
<p>
The <c>-Werror</c> option for <c>erlc</c> and the
compiler option <c>warnings_as_errors</c> will cause
warnings to be treated as errors. (Thanks to Christopher
Faulet.)</p>
<p>
Own Id: OTP-8382</p>
</item>
<item>
<p>Macros overloading has been implemented. (Thanks to
Christopher Faulet.)</p>
<p>
Own Id: OTP-8388</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6.4</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>The compiler's 'E' option now works with modules with
types and specifications.</p>
<p>
Own Id: OTP-8238 Aux Id: OTP-8150 </p>
</item>
<item>
<p>
Certain uses of binary matching in a
<c>begin</c>-<c>end</c> in a list comprehension could
cause the compiler to crash or generate incorrect code.</p>
<p>
Own Id: OTP-8271</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The documentation is now built with open source tools
(xsltproc and fop) that exists on most platforms. One
visible change is that the frames are removed.</p>
<p>
Own Id: OTP-8201</p>
</item>
<item>
<p>
The compiler could crash if invalid calls to is_record/2
was used in (for example) a list comprehension. (Thanks
to Tobias Lindahl.)</p>
<p>
Own Id: OTP-8269</p>
</item>
<item>
<p>The -on_load() directive can be used to run a function
when a module is loaded. It is documented in the section
about code loading in the Reference Manual.</p>
<p>
Own Id: OTP-8295</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6.3</title>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>Corrected liveness optimization to eliminate a
compiler crash that could occur when compiling bit syntax
construction code. (Thanks to Mikage Sawatari.)</p>
<p>Calling BIFs such as <c>length/1</c> in guard context
in a try/catch block could cause a compiler crash.
(Thanks to Paul Fisher.)</p>
<p>Using filter expressions containing <c>andalso</c> or
<c>orelse</c> in a list comprehension could cause a
compiler crash. (Thanks to Martin Engström.)</p>
<p>
Own Id: OTP-8054</p>
</item>
<item>
<p>
A guard with nested 'not' operators could cause the
compiler to crash. (Thanks to Tuncer Ayaz.)</p>
<p>
Own Id: OTP-8131</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6.2</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
The compiler would crash while compiling certain complex
function bodies containing <c>receive after</c> due to a
bug in the jump optimizer (a label that had only had
backward references could still be removed). (Thanks to
Vincent de Phily.)</p>
<p>
Own Id: OTP-7980</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Miscellaneous minor bugs fixed.</p>
<p>
Own Id: OTP-7937</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
There will be more efficient code if there is a clause
that matches the empty binary and no other clauses that
matches non-empty binaries.</p>
<p>
Own Id: OTP-7924</p>
</item>
<item>
<p>There is new option to allow a module to have a module
name other than the filename. Do not use it unless you
know what you are doing.</p>
<p>
Own Id: OTP-7927</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6.0.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>Using <c>andalso</c>/<c>orelse</c> or record access in
a <c>try</c>...<c>catch</c> could cause a compiler
crash.</p>
<p>Som large and complex functions could require
extremely long compilation times (hours or days).</p>
<p>
Own Id: OTP-7905</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.6</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
For some complex guards which used
<c>andalso</c>/<c>orelse</c>, the compiler would crash.
(Thanks to Hunter Morris.)</p>
<p>
Own Id: OTP-7679</p>
</item>
<item>
<p>
Code that (incorrectly) used the the value of nested
applications of <c>setelement/3</c> in bit syntax
construction could crash the compiler.</p>
<p>
Own Id: OTP-7690</p>
</item>
<item>
<p>Modules containing huge integers (consisting of
several hundreds of thousands of digits or more) could be
slow to compile. This problem has been corrected.</p>
<p>
Own Id: OTP-7707 Aux Id: seq11129 </p>
</item>
<item>
<p>If the generator in a list comprehension is given a
non-list term, there will now be <c>function_clause</c>
exception instead of a <c>case_clause</c> exception (as
it was in all releases before R12B).</p>
<p>
Own Id: OTP-7844</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The compiler could crash if the size for a binary segment
in matching was a complex literal such as binary or
tuple.</p>
<p>
Own Id: OTP-7650</p>
</item>
<item>
<p>
The compiler generates more compact and faster code for
matching of complex constants (such as constant lists and
tuples).</p>
<p>
Own Id: OTP-7655</p>
</item>
<item>
<p>
The undocumented, unsupported, and deprecated guard BIF
<c>is_constant/1</c> has been removed.</p>
<p>
*** INCOMPATIBILITY with R12B ***</p>
<p>
Own Id: OTP-7673</p>
</item>
<item>
<p>The compiler generates better code for many guard
expressions, and especially for guards that use
<c>andalso</c>/<c>orelse</c> or record fields.</p>
<p>(In technical terms, <c>andalso</c>/<c>orelse</c> in a
guard would case the creation of a stack frame and saving
of all x registers that could potentially be alive after
the guard and restoring all x registers before leaving
the guard. For certain guards, far too many x registers
were saved and subsequently restored. In this version of
the compiler, no stack frame is created and no x
registers are saved and restored.)</p>
<p>
Own Id: OTP-7718</p>
</item>
<item>
<p>The default size for the resulting binary created by a
binary comprehension was 64Kb in R12B (it would grow if
needed). This was often far too much. In this release,
the default is changed to 256 bytes. Furthermore, for
most binary comprehensions without filters, the exact
size of the resulting binary can be calculated beforehand
and the compiler now generates code that does that
calculation.</p>
<p>
Own Id: OTP-7737</p>
</item>
<item>
<p>The short-circuit operators <c>andalso</c> and
<c>orelse</c> no longer guarantees that their second
argument is either <c>true</c> or <c>false</c>. As a
consequence, <c>andalso</c>/<c>orelse</c> are now
tail-recursive.</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-7748</p>
</item>
<item>
<p>The compiler will refuse to a compile file where the
module name in the file differs from the output file
name.</p>
<p>When compiling using <c>erlc</c>, the current working
directory will no be included in the code path (unless
explicitly added using "-pa .").</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-7793</p>
</item>
<item>
<p>There will no longer be any warnings for list
comprehensions without generators, as such list
comprehension have turned out to be useful.</p>
<p>
Own Id: OTP-7846</p>
</item>
<item>
<p>Warnings for obsolete guard tests are now turned on.
(That is, writing <c>list(L)</c> in a guard instead of
<c>is_list(L)</c> will generate a warning.)</p>
<p>The warnings can be turned off using the
<c>nowarn_obsolete_guard</c> option.</p>
<p>
Own Id: OTP-7850</p>
</item>
<item>
<p>The copyright notices have been updated.</p>
<p>
Own Id: OTP-7851</p>
</item>
<item>
<p>If a module contains an exported function with the
same name as an auto-imported BIF (such as
<c>length/1</c>), any calls to the BIF must have an
explicit <c>erlang:</c> prefix, or there will be a
compilation error (such calls would only generate a
warning in previous releases).</p>
<p>(The reason for the change is to avoid breaking code
in a future major release, R14 or R15, in which we plan
to make calls without a module prefix always call the
local function in the same module even if there is an
auto-imported BIF with the same name.)</p>
<p>
*** POTENTIAL INCOMPATIBILITY ***</p>
<p>
Own Id: OTP-7873</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.5</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>Matching on a zero-width segment in the bit syntax
would crash the compiler. (Thanks to Will.)</p>
<p>
Own Id: OTP-7591</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
In bit syntax expressions which started with a binary
segment, and was followed by at least two segments of
variable size, too little space could be allocated for
the binary, leading to memory corruption.</p>
<p>
Own Id: OTP-7556</p>
</item>
<item>
<p>In user-defined attributes, <c>Name/Arity</c> is now
allowed and will be translated to <c>{Name,Arity}</c>.
(An implementation of EEP-24 by Richard O'Keefe.)</p>
<p>The <c>module_info/{0,1}</c> functions automatically
inserted into each compiled modules are now documented in
the Modules section in the Reference Manual.</p>
<p>
Own Id: OTP-7586</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.4</title>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Certain complex bit syntax matching operations matching
out binaries and having several clauses could give
incorrect results (the matched out binaries were too
short). (Thanks to Christian von Roques for bug report
and correction.)</p>
<p>
Own Id: OTP-7498</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.3</title>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
New option <c>warn_export_all</c> to warn for a module
using <c>export_all</c>. (Thanks to Richard Carlsson.)</p>
<p>
Own Id: OTP-7392</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.2.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
In rare circumstances, the length/1 BIF (and a few other
guard BIFs) would seem to return an incorrect value (of
any type).</p>
<p>
Own Id: OTP-7345 Aux Id: seq10962 </p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.2</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>A bug in the old inliner has been fixed. Some
undocumented functionality has been removed.</p>
<p>
Own Id: OTP-7223</p>
</item>
<item>
<p>Matching several binary patterns in parallel using the
'=' operator is not allowed (an implementation
limitation), but the compiler did not reject all such
attempts (depending on the patterns, the generated code
might or might not work correctly). Now the compiler
rejects all binary patterns joined by '='.</p>
<p>
Own Id: OTP-7227</p>
</item>
<item>
<p>Complex combinations of record operations and binary
matching could cause the compiler to crash. (Thanks to
Vladimir Klebansky.)</p>
<p>
Own Id: OTP-7233</p>
</item>
<item>
<p>
In rare circumstances, mixing binary matching clauses
with clauses matching other data types, the compiler
could crash.</p>
<p>
Own Id: OTP-7240 Aux Id: seq10916 </p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.1.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
Corrected a compiler bug that could cause a complex
binary matching operation to fail when it shouldn't.
(Thanks to Tomas Stejskal.)</p>
<p>
Own Id: OTP-7188</p>
</item>
<item>
<p>
In unusual circumstances, the environment for a fun could
bind wrong values.</p>
<p>
Own Id: OTP-7202 Aux Id: seq10887 </p>
</item>
<item>
<p>Long sequences of list comprehensions without
generators joined by the '++' operator would cause a code
expansion explosion, which could cause the compiler to
run out of memory. To resolve this problem, in
'<c>[...||...]++Expr</c>', <c>Expr</c> is now evaluated
before the list comprehension. This change <em>is</em>
backwards compatible (see the following note about
evaluation order if you have doubts).</p>
<p>Note about evaluation order: The Reference manual says
that subexpressions are evaluated <em>in any order</em>
before the expression itself. Therefore, in an expression
such as '<c>LeftExpr++RightExpr</c>', you should not
depend on <c>LeftExpr</c> being evaluated before
<c>RightExpr</c> or vice versa. The evaluation order is
only important if the expressions contains and/or depends
on operations with side-effects, such as message passing
or <c>ets</c> operations.</p>
<p>
Own Id: OTP-7206</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5.1</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>
A match expression inside a function call could cause a
false "a term is constructed but never used" warning.</p>
<p>
Own Id: OTP-7018 Aux Id: seq10824 </p>
</item>
<item>
<p>The compiler could crash if a binary tail was matched
out, and then used in a binary append operation. (Thanks
to Oleg Avdeev.)</p>
<p>Similarly, the compiler could crash if a binary tail
was matched out, and then used (incorrectly) in binary
construction in an integer field. (Thanks to Fredrik
Svahn.) Or was incorrectly used in a float field. Or was
used in a binary field with a given length. (Thanks to
Chih - Wei Yu.) </p>
<p>
Own Id: OTP-7022</p>
</item>
<item>
<p>
Matching an empty binary in a record and then using the
same record again could cause a compiler crash. (Thanks
to Fredrik Thulin.)</p>
<p>
Own Id: OTP-7029</p>
</item>
<item>
<p>In rare circumstances, constants containing floating
points and integers could be confused. Example:</p>
<p><c>f(a) -> [1]; f(b) -> [1.0].</c></p>
<p>Both <c>f(a)</c> and <c>f(b)</c> would return
<c>[1]</c>.</p>
<p>
Own Id: OTP-7073</p>
</item>
<item>
<p>Some bit syntax code such as</p>
<p><c>matching d(_,<$lt;$gt;$gt;) -> one; d(0,<$lt;D$gt;$gt;)
->two.</c></p>
<p>could crash the compiler. (Thanks to Simon
Cornish.)</p>
<p>
Own Id: OTP-7094</p>
</item>
<item>
<p>
In unusual circumstances, a call to a fun could fail due
to an unsafe optimization. (Thanks to Simon Cornish.)</p>
<p>
Own Id: OTP-7102</p>
</item>
<item>
<p>
Bit syntax matching with a guard containing two or more
uses of andalso/orelse could cause the compiler to crash.
(Thanks to Mateusz Berezecki.)</p>
<p>
Own Id: OTP-7113</p>
</item>
<item>
<p>
This was only a problem if you generated or wrote your
own Core Erlang code: The Core Erlang optimizer code
could move nested calls such as
<c>erlang:'$lt;'(erlang:length(L), 2)</c> as case expression
into a guard, which would change the semantics. (Thanks
to Robert Virding.)</p>
<p>
Own Id: OTP-7117</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
The compiler could generate suboptimal code for record
updates if the record update code consisted of multiple
source code lines.</p>
<p>
Own Id: OTP-7101</p>
</item>
</list>
</section>
</section>
<section><title>Compiler 4.5</title>
<section><title>Fixed Bugs and Malfunctions</title>
<list>
<item>
<p>The compiler used to allow that a binary field without
size could be used in other positions than at the end in
bit syntax pattern. For instance,
<c><![CDATA[<<B/binary,EmptyBinary/binary>> = Bin]]></c>
used to compile, but now the compilation will fail with
an an error message.</p>
<p>Also, it is now longer permitted to give a literal
string in a binary pattern a type or a size; for
instance, <c><![CDATA[<<"abc"/binary>> = Bin]]></c> will
no longer compile. (In previous releases, there would
always be a <c>badmatch</c> exception at run-time.)</p>
<p>
Own Id: OTP-6885</p>
</item>
</list>
</section>
<section><title>Improvements and New Features</title>
<list>
<item>
<p>
Bitstrings (bit-level) binaries and binary comprehensions
are now part of the language. See the Reference Manual.</p>
<p>
Own Id: OTP-6558</p>
</item>
<item>
<p>
The '<c>compressed</c>' option for the compiler has been
documented.</p>
<p>
Own Id: OTP-6801</p>
</item>
<item>
<p>If the value of a list comprehension is not used, such
as in '<c>[do_something(X) || X <- List], ok</c>', a
result list will no longer be built. For more details,
see the Efficiency Guide.</p>
<p>If the value of an expression is not used, and the
expression has no side effects except for possibly
throwing an exception, a warning will be generated.
Examples: '<c>self(),ok</c>' and
'<c>{error,Reason},ok</c>'.</p>
<p>
Own Id: OTP-6824</p>
</item>
<item>
<p>
Three new functions have been added to the <c>compile</c>
module: <c>noenv_file/2</c>, <c>noenv_forms/2</c>, and
<c>noenv_output_generated/1</c>.</p>
<p>
Own Id: OTP-6829</p>
</item>
<item>
<p>Many bit syntax operations, both construction and
matching, are faster. For further information, see the
Efficiency Guide.</p>
<p>
Own Id: OTP-6838</p>
</item>
<item>
<p>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.</p>
<p>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.</p>
<p>Example 1: In the expression <c>element(BitNum-1,
{1,2,4,8,16,32,64,128})</c>, 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.</p>
<p>Example 2: Literal strings, such as <c>"abc"</c>, 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
<c>[$a,$b,$c]</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,
<c><<"abc"<<</c>) instead of string literals for
infrequently used long strings (such as error
messages).</p>
<p>
Own Id: OTP-6850</p>
</item>
<item>
<p>
Recursive calls now usually consume less stack than in
R11B. See the Efficiency Guide.</p>
<p>
Own Id: OTP-6862 Aux Id: seq10746 </p>
</item>
<item>
<p>Two new guard BIFs have been introduced as a
recommended replacement for <c>size/1</c>. (The
<c>size/1</c> BIF will be removed no earlier than in
R14B.) The BIFs are <c>tuple_size/1</c> to calculate the
size of a tuple and <c>byte_size/1</c> 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).</p>
<p>There is also a new <c>bit_size/1</c> BIF that returns
the exact number of bits that a binary or bitstring
contains.</p>
<p>
Own Id: OTP-6902</p>
</item>
<item>
<p>
The two internal functions <c>erl_bifs:is_bif/3</c> and
<c>erl_bifs:is_guard/3</c> have been removed. They were
unsupported, undocumented, and unmaintained.</p>
<p>
Own Id: OTP-6966</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4.5</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>The compiler would crash if you tried to combine to
non-list literals with '<c><![CDATA[++]]></c>' (for instance,
<c><![CDATA[an_atom++"string"]]></c>).</p>
<p>Own Id: OTP-6630 Aux Id: seq10635 </p>
</item>
</list>
</section>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>Minor Makefile changes.</p>
<p>Own Id: OTP-6689</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4.4</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>Incorrect code could be generated for bit syntax matching
if the old inliner was used with aggressive settings.</p>
<p>Own Id: OTP-6461</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4.3</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>The R10B compiler could generate unsafe
<c><![CDATA[bs_save/bs_restore]]></c> 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
<c><![CDATA[bs_save/bs_restore]]></c> 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.)</p>
<p>Own Id: OTP-6386</p>
</item>
</list>
</section>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>Directives for parse transforms that have been run are
now removed from the abstract code stored when the
debug_info option is given, to prevent the parse
transforms to be run again.</p>
<p>Own Id: OTP-5344</p>
</item>
<item>
<p>Minor improvements in code generation for some guards
expression involving boolean expressions.</p>
<p>Own Id: OTP-6347</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4.2.1</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>The compiler could generate incorrect code for bit syntax
matching consisting of several clauses.</p>
<p>Own Id: OTP-6392 Aux Id: seq10539 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4.2</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>Defining a fun itself containing a fun in an
<c><![CDATA[after]]></c> block of a <c><![CDATA[try]]></c> would cause the
compiler to crash or generate incorrect code. (Thanks to
Tim Rath.)</p>
<p>Shorter compilation times for modules containing with
an extreme number of functions (10000 functions or more).</p>
<p>(The compiled could generate deprecated instructions
for certain bit syntax matching operations.)</p>
<p>Own Id: OTP-6212 Aux Id: seq10446 </p>
</item>
<item>
<p>Fixed several bugs that would cause warnings to be shown
without file name and line number.</p>
<p>Own Id: OTP-6260 Aux Id: seq10461 </p>
</item>
</list>
</section>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>The <c><![CDATA[strict_record_tests]]></c> option is now default;
that is, reading a field from a record using the
<c><![CDATA[Record#record_tag.field]]></c> syntax will fail if
<c><![CDATA[Record]]></c> is not a record of the correct type.</p>
<p>If necessary, the record tests can be turned off by
giving the <c><![CDATA[no_strict_record_tests]]></c> option. To avoid
editing Makefiles, the environment variable
<c><![CDATA[ERL_COMPILER_OPTIONS]]></c> can be set to
"<c><![CDATA[no_strict_record_tests]]></c>".</p>
<p>The <c><![CDATA[no_strict_record_tests]]></c> option will probably
be removed in the R12B release.</p>
<p>*** POTENTIAL INCOMPATIBILITY ***</p>
<p>Own Id: OTP-6294</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4.1</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>The compiler used to crash if a module contained code
similar to '<c><![CDATA[fun(1=0) -> ok end]]></c>'. (Thanks to
Richard Carlsson.)</p>
<p>The compiler would spend really long time compiling
bit syntax expressions such as
'<c><![CDATA[<<1:(50*1024*1024)>>]]></c>' and produce a huge .beam
file. Corrected.</p>
<p>The compiler would compile list comprehensions with
many generators really, really slow. (Thanks to Thomas
Raes.)</p>
<p>Module attributes would be stored in reverse order
compared to the order in the source code. (Thus,
<c><![CDATA[M:module_info(attributes)]]></c> would also return the
attributes in reversed order.)</p>
<p>Defining a fun in an <c><![CDATA[after]]></c> block of a
<c><![CDATA[try]]></c> would cause the compiler to crash or generate
incorrect code. (Thanks to Martin Bjorklund.)</p>
<p>The combination of binary pattern and a guard with
andalso/orelse could cause the compiler to crash.</p>
<p>Own Id: OTP-6121 Aux Id: seq10400 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.4</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>When a <c><![CDATA[.hrl]]></c> file is included using
<c><![CDATA[-include_lib]]></c>, the include path is temporarily
updated to include the directory the <c><![CDATA[.hrl]]></c> file was
found in, which will allow that <c><![CDATA[.hrl]]></c> file to itself
include files from the same directory using
<c><![CDATA[-include]]></c>. (Thanks to Richard Carlsson.)</p>
<p>Own Id: OTP-5944</p>
</item>
</list>
</section>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>The <c><![CDATA[andalso]]></c> and <c><![CDATA[orelse]]></c> operators are
now allowed to be used in guards. That also applies to
match specifications.</p>
<p>Own Id: OTP-5894 Aux Id: OTP-5149 </p>
</item>
<item>
<p>When given the new option
<c><![CDATA[strict_record_tests]]></c>, the compiler will generate
code that verifies the record type for
<c><![CDATA[R#record.field]]></c> operations in guards. Code that
verifies record types in bodies has already been
generated since R10B, but in this release there will be a
<c><![CDATA[{badrecord,RecordTag}]]></c> instead of a
<c><![CDATA[badmatch]]></c> if the record verification test fails.
See <c><![CDATA[compile(3)]]></c> for more information.</p>
<p>The Erlang shell always applies strict record tests.</p>
<p>Own Id: OTP-5915 Aux Id: OTP-5714 </p>
</item>
<item>
<p>The BIF <c><![CDATA[is_record/3]]></c> can now be used in guards.
Also, <c><![CDATA[is_record/3]]></c> can now be called without an
<c><![CDATA[erlang:]]></c> module prefix for consistency with the other
<c><![CDATA[is_*]]></c> functions.</p>
<p>Own Id: OTP-5916</p>
</item>
<item>
<p>The compiler options <c><![CDATA[ignore_try]]></c> and
<c><![CDATA[ignore_cond]]></c>, which allowed code that used
unquoted <c><![CDATA[try]]></c> or <c><![CDATA[cond]]></c> as atoms or record
tags, has been removed. Old code that depended on the
options need to be revised to have occurrences of
<c><![CDATA[try]]></c> or <c><![CDATA[cond]]></c> as atom or record tags
single-quoted. (Note: Although <c><![CDATA[cond]]></c> is a reserved
keyword, there is no <c><![CDATA[cond]]></c> statement. It might be
introduced in a future release.)</p>
<p>*** POTENTIAL INCOMPATIBILITY ***</p>
<p>Own Id: OTP-6058</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.12</title>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>The following code would crash the compiler: <c><![CDATA[case T of #r{s = ""} -> T #r{s = "x"} end]]></c>. (Thanks to
Richard Carlsson.)</p>
<p>The compiler could crash if binaries were constructed
in certain guards involving boolean operators (including
semicolon). (Thanks to Torbjorn Tornkvist.)</p>
<p>Own Id: OTP-5872</p>
</item>
<item>
<p>The compiler will now warn that the
<c><![CDATA[megaco:format_versions/1]]></c> function is deprecated.</p>
<p>Own Id: OTP-5976</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.11</title>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>The compiler would assume that some patterns with
aliases ('=') would not match if they were split into
several lines. (Thanks to Peter Nagy/Mats Cronqvist.)</p>
<p>Minor cleanups to eliminate Dialyzer warnings.</p>
<p>Own Id: OTP-5791 Aux Id: seq10141 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.10</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>When given the new option
<c><![CDATA[strict_record_tests]]></c>, the compiler will generate
code that verifies the record type for
<c><![CDATA[R#record.field]]></c> operations (in body context only,
not in guards). See the documentation for the
<c><![CDATA[compile]]></c> module for more information.</p>
<p>The beam validator pass of the compiler could crash
given in rare circumstances when given certain
combinations of catches and record operations. (Thanks to
Mats Cronqvist.)</p>
<p>Attributes containing binaries (such as -a(<<1,2,3>>))
would crash the compiler. (Thanks to Roger Price.)</p>
<p>Multiple behaviours in the same module will no longer
generate a warning, unless one or more callbacks for the
behaviours overlap. For instance, using both the
<c><![CDATA[application]]></c> and <c><![CDATA[supervisor]]></c> behaviours
in the same module will NOT generate any warning, but
using <c><![CDATA[gen_server]]></c> and <c><![CDATA[gen_fsm]]></c> will.</p>
<p>Own Id: OTP-5714 Aux Id: seq10073 </p>
</item>
<item>
<p>The pre-processor used to complain that the macro
definition <c><![CDATA[-define(S(S), ??S).]]></c> was circular,
which it isn't. (Thanks to Richard Carlsson.)</p>
<p>Own Id: OTP-5777</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.9</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>Updating at least two fields of a record with a literal
string could cause the compiler to generate dangerous
code that could cause a crash at run-time (e.g.
<c><![CDATA[R#r{a="abc",b=1}]]></c>). (Thanks to Mikael Karlsson.)</p>
<p>Unecessary tests (such as a 'case' with two case
branches that were identical) could cause the compiler to
crash. (Thanks to Fredrik Thulin.)</p>
<p>The validation pass of the compiler could generate an
error for correct code when floating point operations
were used in try/catch statements.</p>
<p>In bit syntax construction, any field following a
binary field would always be marked as "aligned" (which
may or may not be correct). That would cause the hipe
native compiler to generate incorrect code if the field
was in fact unaligned. (Thanks to Per Gustafsson.)</p>
<p>Some complex guard expressions (such as <c><![CDATA[A#a.b==""; A#a.b==undefined]]></c>) would crash the compiler. (Thanks
to Sean Hinde.)</p>
<p>Compilation speed has been increased for modules with
many functions and/or atoms (such as modules generated by
the Asn1 application or other code generators).</p>
<p>Own Id: OTP-5632 Aux Id: seq10057 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.8</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>In some circumstances, having two try/catch constructs
following each in a function body, would cause an
internal error to be generated (when in fact the
generated code was correct). (Thanks to Fredrik Thulin.)</p>
<p>Incorrect calls such as <c><![CDATA[M:42()]]></c> would crash the
compiler. The compiler now generates a warning. (Thanks
to Ulf Wiger.)</p>
<p>Own Id: OTP-5553</p>
</item>
</list>
</section>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>The new <c><![CDATA[fun M:F/A]]></c> construct creates a fun that
refers to the latest version of <c><![CDATA[M:F/A]]></c>. This syntax is
meant to replace tuple funs <c><![CDATA[{M,F}]]></c> which have many
problems.</p>
<p>The new type test <c><![CDATA[is_function(Fun, A)]]></c> (which may be
used in guards) test whether <c><![CDATA[Fun]]></c> is a fun that can be
applied with <c><![CDATA[A]]></c> arguments. (Currently, <c><![CDATA[Fun]]></c> can
also be a tuple fun.)</p>
<p>Own Id: OTP-5584</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.7</title>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>Further improvements of encrypted debug info: New option
<c><![CDATA[encrypt_debug_info]]></c> for compiler.</p>
<p>Own Id: OTP-5541 Aux Id: seq9837 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.6</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>Fixed a bug in the validator of the generated code
(beam_validator) which caused an internal compiler error
even though the generated code was indeed correct.</p>
<p>Own Id: OTP-5481 Aux Id: seq9798 </p>
</item>
</list>
</section>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>It is now possible to encrypt the debug information in
Beam files, to help keep the source code secret. See the
documentation for <c><![CDATA[compile]]></c> on how to provide the key
for encrypting, and the documentation for <c><![CDATA[beam_lib]]></c>
on how to provide the key for decryption so that tools such
as the Debugger, Xref, or Cover can be used.</p>
<p>The <c><![CDATA[beam_lib:chunks/2]]></c> functions now accepts an
additional chunk type <c><![CDATA[compile_info]]></c> to retrieve
the compilation information directly as a term. (Thanks
to Tobias Lindahl.)</p>
<p>Own Id: OTP-5460 Aux Id: seq9787 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.5</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>Complex functions could cause the internal validator in
the compiler to generate an internal error even though
the generated code was correct.</p>
<p>Own Id: OTP-5436 Aux Id: seq9781 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.4</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>In rare circumstances, incorrect code for record or
tuple access could be generated. The incorrect code would
either trigger an internal error in the compiler or cause
an exception at run time. (Thanks to Martin Bjorklund.)</p>
<p>Corrected a bug in in bit syntax matching where
clauses could match in the wrong order. (Thanks to Ulf
Wiger.)</p>
<p>Own Id: OTP-5404 Aux Id: seq9767 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.3</title>
<section>
<title>Improvements and New Features</title>
<list type="bulleted">
<item>
<p>Given bit syntax construction in certain complex
contexts involving a catch, the compiler would either
crash or terminate due to failure in an internal
consistency check. (Thanks to Fredrik Thulin.)</p>
<p>Matches such as
<c><![CDATA[<<103133:64/float>> = <<103133:64/float>>]]></c>
used to fail. Now they succeed.</p>
<p>Shadowing of variables in bit syntax matches in fun heads
such as in
<c><![CDATA[L = 8, F = fun(<<L:L,B:L>>) -> B end]]></c> was
handled incorrectly by the compiler. The fun used to be
compiled as if it was written
'<c><![CDATA[>fun(<<8:8,B:8>>)]]></c>, while it should be
compiled in the same way as <c><![CDATA[fun(<<L:8,B:L>>)]]></c>.</p>
<p>A bug in the validation pass has been corrected. It
sometimes occurred when the compiler optimized by reusing
code for causing an exception when the reused code was
called from within catch or try-catch statements. Then the
validator refused to approve the code and complained about
<c><![CDATA[fun(<<L:L,B:L>>) -> B end]]></c> was handled
incorrectly by the in the same way as
<c><![CDATA[fun(<<L:8,B:L>>)]]></c>.</p>
<p>A bug in the unknown_catch_try_state.</p>
<p>Corrected a bug in the optimizer that would cause
the compiler to crash. (Thanks to Peter-Henry Mander.)</p>
<p>There are now warnings generated if a bit syntax
construction will fail at run-time because of a type
mismatch (e.g. <c><![CDATA[<<an_atom:8>>]]></c>).</p>
<p>Own Id: OTP-5342 Aux Id: OTP-5118, OTP-5270, OTP-5323 </p>
</item>
<item>
<p>Binary pattern matching such as
<c><![CDATA[t(<<A:8>> = <<A:8>)]]></c> used to silently
fail at runtime (i.e. never match). The compiler now
generates an error for any such patterns.</p>
<p>Own Id: OTP-5371</p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.2</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>In rare cases, the code compiler code generate code
for a tuple match that could crash the emulator if passed
a term that was not a tuple.</p>
<p>If a bit syntax construction failed within a catch,
previously assigned variables could get the wrong value.</p>
<p>The compiler now runs a validation pass on the
generated code and aborts before writing a Beam file if
any suspect code is found. In particular, the validation
pass checks for incorrect code that may cause emulator
crashes or other strange symptoms in the emulator.</p>
<p>Some corrections to the unsupported feature
parameterized modules by Richard Carlsson (HiPE).</p>
<p>Own Id: OTP-5247 Aux Id: OTP-5235 </p>
</item>
</list>
</section>
</section>
<section>
<title>Compiler 4.3.1</title>
<section>
<title>Fixed Bugs and Malfunctions</title>
<list type="bulleted">
<item>
<p>Corrected the release note regarding <c><![CDATA[try/catch]]></c> below.
<c><![CDATA[try/catch]]></c> DOES work in the initial R10B release.</p>
<p>A few minor issues code generation issues were corrected.
Although the generated code was correct, it was slightly
slower and larger than it needed to be.</p>
<p>A debug printout (that could be seen in rare
circumstances) has been removed.</p>
<p><c><![CDATA[not record_test(not_a_tuple, RecordTag)]]></c> and
similar expressions in a guard would fail.</p>
<p>New options <c><![CDATA[basic_validation]]></c> and
<c><![CDATA[strong_validation]]></c> to do a quick check of the code
of a module.</p>
<p>The <c><![CDATA[inline]]></c> option was not recognized if it
appeared in a <c><![CDATA[-compile()]]></c> directive inside the
module.</p>
<p>Corrected some bugs in the undocumented feature
"parameterized modules".</p>
<p>Own Id: OTP-5198</p>
</item>
<item>
<p>When the undocumented feature "parameterized modules" was
used, the <c><![CDATA[?MODULE]]></c> macro did not work correctly.</p>
<p>Own Id: OTP-5224</p>
</item>
</list>
</section>
</section>
</chapter>
