<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2004</year><year>2010</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights 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 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 Engstr�m.)</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>
