1 Compiler Release Notes
This document describes the changes made to the Compiler
application.
1.1 Compiler 4.5
1.1.1 Fixed Bugs and Malfunctions
-
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,
<<B/binary,EmptyBinary/binary>> = Bin
used to compile, but now the compilation will fail with
an an error message.
Also, it is now longer permitted to give a literal
string in a binary pattern a type or a size; for
instance, <<"abc"/binary>> = Bin will
no longer compile. (In previous releases, there would
always be a badmatch exception at run-time.)
Own Id: OTP-6885
1.1.2 Improvements and New Features
-
Bitstrings (bit-level) binaries and binary comprehensions
are now part of the language. See the Reference Manual.
Own Id: OTP-6558
-
The 'compressed' option for the compiler has been
documented.
Own Id: OTP-6801
-
If the value of a list comprehension is not used, such
as in '[do_something(X) || X <- List], ok', a
result list will no longer be built. For more details,
see the Efficiency Guide.
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: 'self(),ok' and
'{error,Reason},ok'.
Own Id: OTP-6824
-
Three new functions have been added to the compile
module: noenv_file/2, noenv_forms/2, and
noenv_output_generated/1.
Own Id: OTP-6829
-
Many bit syntax operations, both construction and
matching, are faster. For further information, see the
Efficiency Guide.
Own Id: OTP-6838
-
Literal lists, tuples, and binaries are no longer
constructed at run-time as they used to be, but are
stored in a per-module constant pool. Literals that are
used more than once are stored only once.
This is not a change to the language, only in the
details of its implementation. Therefore, the
implications of this change is described in the
Efficiency Guide.
Example 1: In the expression element(BitNum-1,
{1,2,4,8,16,32,64,128}), the tuple used to be
constructed every time the expression was executed, which
could be detrimental to performance in two ways if the
expression was executed in a loop: the time to build the
tuple itself and the time spent in garbage collections
because the heap filled up with garbage faster.
Example 2: Literal strings, such as "abc", used
to be stored in the compiled code compactly as a byte
string and expanded to a list at run-time. Now all
strings will be stored expanded to lists (such as
[$a,$b,$c]) in the constant pool. That means that
the string will be faster to use at run-time, but that it
will require more space even when not used. If space is
an issue, you might want to use binary literals (that is,
<<"abc"<<) instead of string literals for
infrequently used long strings (such as error
messages).
Own Id: OTP-6850
-
Recursive calls now usually consume less stack than in
R11B. See the Efficiency Guide.
Own Id: OTP-6862 Aux Id: seq10746
-
Two new guard BIFs have been introduced as a
recommended replacement for size/1. (The
size/1 BIF will be removed no earlier than in
R14B.) The BIFs are tuple_size/1 to calculate the
size of a tuple and byte_size/1 to calculate the
number of bytes needed for the contents of the binary or
bitstring (rounded up to the nearest number of bytes if
necessary).
There is also a new bit_size/1 BIF that returns
the exact number of bits that a binary or bitstring
contains.
Own Id: OTP-6902
-
The two internal functions erl_bifs:is_bif/3 and
erl_bifs:is_guard/3 have been removed. They were
unsupported, undocumented, and unmaintained.
Own Id: OTP-6966
1.2 Compiler 4.4.5
1.2.1 Fixed Bugs and Malfunctions
-
The compiler would crash if you tried to combine to
non-list literals with '++' (for instance,
an_atom++"string").
Own Id: OTP-6630 Aux Id: seq10635
1.2.2 Improvements and New Features
-
Minor Makefile changes.
Own Id: OTP-6689
1.3 Compiler 4.4.4
1.3.1 Fixed Bugs and Malfunctions
-
Incorrect code could be generated for bit syntax matching
if the old inliner was used with aggressive settings.
Own Id: OTP-6461
1.4 Compiler 4.4.3
1.4.1 Fixed Bugs and Malfunctions
-
The R10B compiler could generate unsafe
bs_save/bs_restore instructions that could cause
memory corruption. (The R11B compiler does not have that
problem.) The erlang emulator will now refuse to load
R10B-compiled modules that contain such unsafe
bs_save/bs_restore instructions. In addition, the
beam_validator module in the compiler will also reject
such instructions (in case it is used to validate R10B
code). (Thanks to Matthew Reilly.)
Own Id: OTP-6386
1.4.2 Improvements and New Features
-
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.
Own Id: OTP-5344
-
Minor improvements in code generation for some guards
expression involving boolean expressions.
Own Id: OTP-6347
1.5 Compiler 4.4.2.1
1.5.1 Fixed Bugs and Malfunctions
-
The compiler could generate incorrect code for bit syntax
matching consisting of several clauses.
Own Id: OTP-6392 Aux Id: seq10539
1.6 Compiler 4.4.2
1.6.1 Fixed Bugs and Malfunctions
-
Defining a fun itself containing a fun in an
after block of a try would cause the
compiler to crash or generate incorrect code. (Thanks to
Tim Rath.)
Shorter compilation times for modules containing with
an extreme number of functions (10000 functions or more).
(The compiled could generate deprecated instructions
for certain bit syntax matching operations.)
Own Id: OTP-6212 Aux Id: seq10446
-
Fixed several bugs that would cause warnings to be shown
without file name and line number.
Own Id: OTP-6260 Aux Id: seq10461
1.6.2 Improvements and New Features
-
The strict_record_tests option is now default;
that is, reading a field from a record using the
Record#record_tag.field syntax will fail if
Record is not a record of the correct type.
If necessary, the record tests can be turned off by
giving the no_strict_record_tests option. To avoid
editing Makefiles, the environment variable
ERL_COMPILER_OPTIONS can be set to
"no_strict_record_tests".
The no_strict_record_tests option will probably
be removed in the R12B release.
*** POTENTIAL INCOMPATIBILITY ***
Own Id: OTP-6294
1.7 Compiler 4.4.1
1.7.1 Fixed Bugs and Malfunctions
-
The compiler used to crash if a module contained code
similar to 'fun(1=0) -> ok end'. (Thanks to
Richard Carlsson.)
The compiler would spend really long time compiling
bit syntax expressions such as
'<<1:(50*1024*1024)>>' and produce a huge .beam
file. Corrected.
The compiler would compile list comprehensions with
many generators really, really slow. (Thanks to Thomas
Raes.)
Module attributes would be stored in reverse order
compared to the order in the source code. (Thus,
M:module_info(attributes) would also return the
attributes in reversed order.)
Defining a fun in an after block of a
try would cause the compiler to crash or generate
incorrect code. (Thanks to Martin Bjorklund.)
The combination of binary pattern and a guard with
andalso/orelse could cause the compiler to crash.
Own Id: OTP-6121 Aux Id: seq10400
1.8 Compiler 4.4
1.8.1 Fixed Bugs and Malfunctions
-
When a .hrl file is included using
-include_lib, the include path is temporarily
updated to include the directory the .hrl file was
found in, which will allow that .hrl file to itself
include files from the same directory using
-include. (Thanks to Richard Carlsson.)
Own Id: OTP-5944
1.8.2 Improvements and New Features
-
The andalso and orelse operators are
now allowed to be used in guards. That also applies to
match specifications.
Own Id: OTP-5894 Aux Id: OTP-5149
-
When given the new option
strict_record_tests, the compiler will generate
code that verifies the record type for
R#record.field operations in guards. Code that
verifies record types in bodies has already been
generated since R10B, but in this release there will be a
{badrecord,RecordTag} instead of a
badmatch if the record verification test fails.
See compile(3) for more information.
The Erlang shell always applies strict record tests.
Own Id: OTP-5915 Aux Id: OTP-5714
-
The BIF is_record/3 can now be used in guards.
Also, is_record/3 can now be called without an
erlang: module prefix for consistency with the other
is_* functions.
Own Id: OTP-5916
-
The compiler options ignore_try and
ignore_cond, which allowed code that used
unquoted try or cond as atoms or record
tags, has been removed. Old code that depended on the
options need to be revised to have occurrences of
try or cond as atom or record tags
single-quoted. (Note: Although cond is a reserved
keyword, there is no cond statement. It might be
introduced in a future release.)
*** POTENTIAL INCOMPATIBILITY ***
Own Id: OTP-6058
1.9 Compiler 4.3.12
1.9.1 Improvements and New Features
-
The following code would crash the compiler: case T of #r{s = ""} -> T #r{s = "x"} end. (Thanks to
Richard Carlsson.)
The compiler could crash if binaries were constructed
in certain guards involving boolean operators (including
semicolon). (Thanks to Torbjorn Tornkvist.)
Own Id: OTP-5872
-
The compiler will now warn that the
megaco:format_versions/1 function is deprecated.
Own Id: OTP-5976
1.10 Compiler 4.3.11
1.10.1 Improvements and New Features
-
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.)
Minor cleanups to eliminate Dialyzer warnings.
Own Id: OTP-5791 Aux Id: seq10141
1.11 Compiler 4.3.10
1.11.1 Fixed Bugs and Malfunctions
-
When given the new option
strict_record_tests, the compiler will generate
code that verifies the record type for
R#record.field operations (in body context only,
not in guards). See the documentation for the
compile module for more information.
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.)
Attributes containing binaries (such as -a(<<1,2,3>>))
would crash the compiler. (Thanks to Roger Price.)
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
application and supervisor behaviours
in the same module will NOT generate any warning, but
using gen_server and gen_fsm will.
Own Id: OTP-5714 Aux Id: seq10073
-
The pre-processor used to complain that the macro
definition -define(S(S), ??S). was circular,
which it isn't. (Thanks to Richard Carlsson.)
Own Id: OTP-5777
1.12 Compiler 4.3.9
1.12.1 Fixed Bugs and Malfunctions
-
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.
R#r{a="abc",b=1}). (Thanks to Mikael Karlsson.)
Unecessary tests (such as a 'case' with two case
branches that were identical) could cause the compiler to
crash. (Thanks to Fredrik Thulin.)
The validation pass of the compiler could generate an
error for correct code when floating point operations
were used in try/catch statements.
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.)
Some complex guard expressions (such as A#a.b==""; A#a.b==undefined) would crash the compiler. (Thanks
to Sean Hinde.)
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).
Own Id: OTP-5632 Aux Id: seq10057
1.13 Compiler 4.3.8
1.13.1 Fixed Bugs and Malfunctions
-
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.)
Incorrect calls such as M:42() would crash the
compiler. The compiler now generates a warning. (Thanks
to Ulf Wiger.)
Own Id: OTP-5553
1.13.2 Improvements and New Features
-
The new fun M:F/A construct creates a fun that
refers to the latest version of M:F/A. This syntax is
meant to replace tuple funs {M,F} which have many
problems.
The new type test is_function(Fun, A) (which may be
used in guards) test whether Fun is a fun that can be
applied with A arguments. (Currently, Fun can
also be a tuple fun.)
Own Id: OTP-5584
1.14 Compiler 4.3.7
1.14.1 Improvements and New Features
-
Further improvements of encrypted debug info: New option
encrypt_debug_info for compiler.
Own Id: OTP-5541 Aux Id: seq9837
1.15 Compiler 4.3.6
1.15.1 Fixed Bugs and Malfunctions
-
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.
Own Id: OTP-5481 Aux Id: seq9798
1.15.2 Improvements and New Features
-
It is now possible to encrypt the debug information in
Beam files, to help keep the source code secret. See the
documentation for compile on how to provide the key
for encrypting, and the documentation for beam_lib
on how to provide the key for decryption so that tools such
as the Debugger, Xref, or Cover can be used.
The beam_lib:chunks/2 functions now accepts an
additional chunk type compile_info to retrieve
the compilation information directly as a term. (Thanks
to Tobias Lindahl.)
Own Id: OTP-5460 Aux Id: seq9787
1.16 Compiler 4.3.5
1.16.1 Fixed Bugs and Malfunctions
-
Complex functions could cause the internal validator in
the compiler to generate an internal error even though
the generated code was correct.
Own Id: OTP-5436 Aux Id: seq9781
1.17 Compiler 4.3.4
1.17.1 Fixed Bugs and Malfunctions
-
In rare circumstances, inccorrect 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.)
Corrected a bug in in bit syntax matching where
clauses could match in the wrong order. (Thanks to Ulf
Wiger.)
Own Id: OTP-5404 Aux Id: seq9767
1.18 Compiler 4.3.3
1.18.1 Improvements and New Features
-
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.)
Matches such as
<<103133:64/float>> = <<103133:64/float>>
used to fail. Now they succeed.
Shadowing of variables in bit syntax matches in fun heads
such as in
L = 8, F = fun(<<L:L,B:L>>) -> B end was
handled incorrectly by the compiler. The fun used to be
compiled as if it was written
'>fun(<<8:8,B:8>>), while it should be
compiled in the same way as fun(<<L:8,B:L>>).
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
fun(<<L:L,B:L>>) -> B end was handled
incorrectly by the in the same way as
fun(<<L:8,B:L>>).
A bug in the unknown_catch_try_state.
Corrected a bug in the optimizer that would cause
the compiler to crash. (Thanks to Peter-Henry Mander.)
There are now warnings generated if a bit syntax
construction will fail at run-time because of a type
mismatch (e.g. <<an_atom:8>>).
Own Id: OTP-5342 Aux Id: OTP-5118, OTP-5270, OTP-5323
-
Binary pattern mattern such as
t(<<A:8>> = <<A:8>) used to silently
fail at runtime (i.e. never match). The compiler now
generates an error for any such patterns.
Own Id: OTP-5371
1.19 Compiler 4.3.2
1.19.1 Fixed Bugs and Malfunctions
-
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.
If a bit syntax construction failed within a catch,
previously assigned variables could get the wrong value.
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.
Some corrections to the unsupported feature
parameterized modules by Richard Carlsson (HiPE).
Own Id: OTP-5247 Aux Id: OTP-5235
1.20 Compiler 4.3.1
1.20.1 Fixed Bugs and Malfunctions
-
Corrected the release note regarding try/catch below.
try/catch DOES work in the initial R10B release.
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.
A debug printout (that could be seen in rare
circumstances) has been removed.
not record_test(not_a_tuple, RecordTag) and
similar expressions in a guard would fail.
New options basic_validation and
strong_validation to do a quick check of the code
of a module.
The inline option was not recognized if it
appeared in a -compile() directive inside the
module.
Corrected some bugs in the undocumented feature
"parameterized modules".
Own Id: OTP-5198
-
When the undocumented feature "parameterized modules" was
used, the ?MODULE macro did not work correctly.
Own Id: OTP-5224
compiler 4.5
Copyright © 1991-2007
Ericsson AB