View Source Compiler Release Notes

This document describes the changes made to the Compiler application.

Compiler 8.5.2

Fixed Bugs and Malfunctions

Fixed a crash in an optimization pass relating to appending binaries.
Own Id: OTP-19168 Aux Id: GH-8630
Fixed a bug in the compiler's alias analysis pass that could make it emit unsafe code.
Own Id: OTP-19178 Aux Id: PR-8686

Compiler 8.5.1

Fixed Bugs and Malfunctions

One of the compiler's optimization passes would get very slow when compiling certain modules. The compiler will now automatically disable that pass for input that would trigger the slowdown.
Own Id: OTP-19131 Aux Id: PR-8567
Fix +deterministic to work properly with documentation attributes.
Own Id: OTP-19142 Aux Id: PR-8585

Compiler 8.5

Fixed Bugs and Malfunctions

Generators for binary comprehensions could be evaluated before it was known that they would be needed. That could result in a binary comprehensions failing if a generator that should not be evaluated until later failed.
As an example, consider this module:
```
-module(t).
-export([f/0]).

f() ->
    <<0 || _ <- [], _ <- ok, false>>.
```
In Erlang/OTP 26 it would fail like so:
```
1> t:f().
** exception error: bad generator ok
     in function  t:f/0 (t.erl, line 6)
```
In Erlang/OTP 27 it returns an empty binary:
```
1> t:f().
<<>>
```
Own Id: OTP-18703 Aux Id: GH-7494, PR-7538
The documentation for the preprocessor now mentions that defined(Name) can be called in the condition for an -if or -elif directive to test whether Name is the name of a defined macro. (This feature was implemented in OTP 21.)
If a function call in an -if or -elif with a name that is not the name of a guard BIF, there would not be a compilation error, but would instead cause the lines following the directive to be skipped. This has now been changed to be a compilation error.
POTENTIAL INCOMPATIBILITY
Own Id: OTP-18784 Aux Id: GH-7706, PR-7726

Improvements and New Features

The compiler now emits nicer error message for function head mismatches. For example, given:

a() -> ok;
a(_) -> error.

Erlang/OTP 26 and earlier would emit a diagnostic similar to:

t.erl:6:1: head mismatch
%    6| a(_) -> error.
%     | ^

while in Erlang/OTP 27 the diagnostic is similar to:

t.erl:6:1: head mismatch: function a with arities 0 and 1 is regarded as two distinct functions. Is the number of arguments incorrect or is the semicolon in a/0 unwanted?
%    6| a(_) -> error.
%     | ^

Own Id: OTP-18648 Aux Id: PR-7383

The compiler now optimizes creation of binaries that are known to be constant.
Consider this example:
```
bin() ->
    C = char(),
    <<C>>.

char() -> $*.
```
Essentially, the compiler rewrites the example to the slightly more efficient:
```
bin() ->
    _ = char(),
    <<$*>>.

char() -> $*.
```
Own Id: OTP-18673 Aux Id: PR-7474, ERIERL-964
The compiler will now merge consecutive updates of the same record.
As an example, the body of the following function will be combined into a single tuple creation instruction:
```
-record(r, {a,b,c,d}).

update(Value) ->
    R0 = #r{},
    R1 = R0#r{a=Value},
    R2 = R1#r{b=2},
    R2#r{c=3}.
```
Own Id: OTP-18680 Aux Id: PR-7491, PR-8086, ERIERL-967
Improved the performance of the alias analysis pass.
Own Id: OTP-18714 Aux Id: PR-7528, GH-7432
-spec attributes are now used for documentation.
Own Id: OTP-18801 Aux Id: PR-7739
Native coverage support has been implemented in the JIT. It will automatically be used by the cover tool to reduce the execution overhead when running cover-compiled code.
There are also new APIs to support native coverage without using the cover tool.
To instrument code for native coverage it must be compiled with the line_coverage option.
To enable native coverage in the runtime system, start it like so:
```
$ erl +JPcover true
```
There are also the following new functions for supporting native coverage:
Own Id: OTP-18856 Aux Id: PR-7856
EEP-59 - Documentation Attributes has been implemented.
Documentation attributes can be used to document functions, types, callbacks, and modules. The keyword -moduledoc "Documentation here". is used to document modules, while -doc "Documentation here". can be used on top of functions, types, and callbacks to document them, respectively.
- Types, callbacks, and function documentation can be set to hidden either via -doc false or -doc hidden. When documentation attributes mark a type as hidden, they will not be part of the documentation.
- The documentation from moduledoc and doc gets added by default to the binary beam file, following the format of EEP-48.
- Using the compiler flag warn_missing_doc will raise a warning when -doc attributes are missing in exported functions, types, and callbacks.
- Using the compiler flag warn_missing_spec_documented will raise a warning when spec attributes are missing in documented functions, types, and callbacks.
- moduledocs and docs may refer to external files to be embedded, such as -doc {file, "README.md"}., which refers to the file README.md found in the current working directory.
- The compiler warns about exported functions whose specs refer to hidden types. Thus, there will be warnings when a hidden type (meaning, the type is not part of the documentation) gets used in an exported function.
Own Id: OTP-18916 Aux Id: PR-7936
The documentation has been migrated to use Markdown and ExDoc.
Own Id: OTP-18955 Aux Id: PR-8026
The order in which the compiler looks up options has changed.
When there is a conflict in the compiler options given in the -compile() attribute and options given to the compiler, the options given in the -compile() attribute overrides the option given to the compiler, which in turn overrides options given in the ERL_COMPILER_OPTIONS environment variable.
Example:
If some_module.erl has the following attribute:
```
-compile([nowarn_missing_spec]).
```
and the compiler is invoked like so:
```
% erlc +warn_missing_spec some_module.erl
```
no warnings will be issued for functions that do not have any specs.
POTENTIAL INCOMPATIBILITY
Own Id: OTP-18968 Aux Id: GH-6979, PR-8093
Safe destructive update of tuples has been implemented in the compiler and runtime system. This allows the VM to update tuples in-place when it is safe to do so, thus improving performance by doing less copying but also by producing less garbage.
Example:
```
-record(rec, {a,b,c}).

update(#rec{a=needs_update,b=N}=R0) ->
    R = R0#rec{a=up_to_date},
    if
        N < 0 ->
            R#rec{c=negative};
        N == 0 ->
            R#rec{c=zero};
        N > 0 ->
            R#rec{c=positive}
    end.
```
The record updates in each of the three clauses of the if can safely be done in-place, because variable R is not used again.
Own Id: OTP-18972 Aux Id: PR-8090
Improved the match context reuse optimization slightly, allowing match contexts to be passed as-is to bit_size/1 and byte_size/1.
Own Id: OTP-18987
erl_lint (and by extension the compiler) will now warn for code using deprecated callbacks.
The only callback currenly deprecated is format_status/2 in gen_server, gen_event and gen_statem.
You can use nowarn_deprecated_callback to silence the warning.
Own Id: OTP-19010 Aux Id: PR-8205

Compiler 8.4.3.1

Fixed Bugs and Malfunctions

Fixed a crash in an optimization pass relating to appending binaries.
Own Id: OTP-19168 Aux Id: GH-8630
Fixed a bug in the compiler's alias analysis pass that could make it emit unsafe code.
Own Id: OTP-19178 Aux Id: PR-8686

Compiler 8.4.3

Fixed Bugs and Malfunctions

In rare circumstances, the compiler code generate unsafe code for a bit syntax match.
Own Id: OTP-19019
In rare circumstances, binary matches that were supposed to succeed failed.
Own Id: OTP-19035 Aux Id: GH-8280, PR-8284
Fixed a bug where a fun's environment could be overridden by an argument if all of the following conditions were met:
- The fun was declared in the module that called it.
- The fun's target was statically known.
- The fun was called with a number of extra arguments equal to the number of environment variables.
Own Id: OTP-19045 Aux Id: GH-8316

Compiler 8.4.2

Fixed Bugs and Malfunctions

In rare circumstances, an unsafe optimization could cause the compiler to generate incorrect code for list matching.
Own Id: OTP-19003 Aux Id: GH-8187, PR-8189

Improvements and New Features

Fix the compilation server to restart if the applications in its lib dir changes inbetween erlc invokations.
Own Id: OTP-18936

Compiler 8.4.1

Fixed Bugs and Malfunctions

The compiler could become extremely slow for modules containing huge functions.
Own Id: OTP-18770 Aux Id: GH-7667, PR-7672

Compiler 8.4

Fixed Bugs and Malfunctions

The compiler could run forever when compiling a call to is_record/3 with a huge positive tuple size. The call is_record(A, a, 0) would crash the compiler when used in a function body. When used in a guard the compiler would emit incorrect code that would accept {a> as a record.
Own Id: OTP-18605 Aux Id: GH-7298, GH-7317
Fixed a bug that caused dialyzer to crash when analyzing bogus code that contained the literal atom undefined in segment sizes.
Own Id: OTP-18629 Aux Id: GH-7325
The compiler would crash when compiling some modules that contained a call to erlang:load_nif/2.
Own Id: OTP-18662 Aux Id: GH-7409, PR-7416
Fixed a bug that caused the compiler to crash on legal code.
Own Id: OTP-18678 Aux Id: GH-7488
The compiler could crash when attempting to compile a call to is_list/1 in a complex expression.
Own Id: OTP-18689 Aux Id: GH-7504, PR-7518
A complex guard expression using the or operator could succeed when it was supposed to fail.
Own Id: OTP-18692 Aux Id: GH-7517, PR-7519
Compiling nested try/catch and catch expression could result in an internal compiler error.
Own Id: OTP-18701 Aux Id: GH-7477, PR-7532
Using the bnot operator in a complex expression could cause the compiler to terminate with an internal consistency failure diagnostic.
Own Id: OTP-18719 Aux Id: GH-7468, PR-7562
Fixed a bug that caused the compiler to crash in a binary optimization pass.
Own Id: OTP-18721 Aux Id: PR-7527
The compiler could terminate with an internal error when attempting to compile a binary pattern that could not possibly match.
Own Id: OTP-18725 Aux Id: GH-7467

Improvements and New Features

Fixed various performance issues related to the alias optimization pass.
Own Id: OTP-18691 Aux Id: PR-7448

Compiler 8.3.2

Fixed Bugs and Malfunctions

Fixed a type handling bug that would cause an internal consistence failure for correct code.
Own Id: OTP-18625 Aux Id: GH-7354
Fixed a bug that could cause the stack trace of throw exceptions to be erroneously optimized out.
Own Id: OTP-18626 Aux Id: GH-7356
Complex guard expression using 'or' were not always fully evaluated, making guards that were supposed to fail succeed.
Own Id: OTP-18634 Aux Id: GH-7370

Compiler 8.3.1

Fixed Bugs and Malfunctions

Fixed a bug where a failing bsl expression in a guard threw an exception instead of causing the guard to fail.
Own Id: OTP-18576
Fixed a bug that would case the validator to reject legal code.
Own Id: OTP-18581 Aux Id: GH-7251
The compiler could re-order clauses matching binaries so that the incorrect clause would match. That could only happen for code that used the option {error_location,line} or for code without line or column number information (e.g. generated by a parse transform).
Own Id: OTP-18583 Aux Id: GH-7259
Complex guard expression using the or operator and guard BIFs that can fail could sometimes be miscompiled so that the guard would succeed even if a call to a guard BIF failed.
Own Id: OTP-18593 Aux Id: GH-7252
With optimizations disabled, a try/catch construct could return an incorrect value.
Own Id: OTP-18600 Aux Id: GH-7248
In rare circumstance, a combination of binary construction and binary_part/3 would cause the compiler to generate unsafe code that would crash the runtime system.
Own Id: OTP-18601
The compiler could be very slow when compiling guards with multiple guard tests separated with 'or' or ';'.
Own Id: OTP-18617 Aux Id: GH-7338
Complex guard expressions using 'or' and map updates could succeed even if the map update failed.
Own Id: OTP-18619 Aux Id: GH-7339

Compiler 8.3

Fixed Bugs and Malfunctions

The compiler would silently accept singleton (unbound) type variables in a union type. Starting from Erlang/OTP 26, the compiler will generate a warning for this example. The warning can be disabled using the nowarn_singleton_typevar option. In Erlang/OTP 27, the warning will become an error.
Own Id: OTP-18389 Aux Id: GH-6508, PR-6864, GH-7116

Improvements and New Features

Optimized record updates.
Own Id: OTP-18126 Aux Id: PR-6033
There are several new optimization for binary syntax in the JIT:
- Creation and matching of binaries with segments of fixed sizes have been optimized.
- Creation and matching of UTF-8 segments have been optimized.
- Appending to binaries has been optimized.
Own Id: OTP-18137 Aux Id: PR-6259, PR-6404, PR-6576, PR-6804
The compiler and JIT now generate better code for creation of small maps where all keys are literals known at compile time.
Own Id: OTP-18185 Aux Id: GH-6139
A limitation in the binary syntax has been removed. It is now possible to match binary patterns in parallel. Example: <<A:8>> = <<B:4,C:4>> = Bin
Own Id: OTP-18297 Aux Id: GH-6348
It is documented that $\^X is the ASCII code for Control X, where X is an uppercase or lowercase letter. However, this notation would work for any character X, even then it didn't make sense.
In Erlang/OTP 26, it is now documented that the following characters are also allowed to follow the \^ characters: @, [, \, ], ^, _, and ?. Attempt to use other characters will be rejected with a compiler error.
The value for $\^? is now 127 (instead of 31 as in earlier releases).
Own Id: OTP-18337 Aux Id: GH-6477, PR-6503
The BIFs min/2 and max/2 are now allowed to be used in guards and match specs.
Own Id: OTP-18367 Aux Id: GH-6544
Map comprehensions as suggested in EEP 58 has now been implemented.
Own Id: OTP-18413 Aux Id: EEP-58, PR-6727
Improved the selective receive optimization, which can now be enabled for references returned from other functions.
This greatly improves the performance of gen_server:send_request/3, gen_server:wait_response/2, and similar functions.
Own Id: OTP-18431 Aux Id: PR-6739
Deprecates dbg:stop_clear/0 because it is simply a function alias to dbg:stop/0
Own Id: OTP-18478 Aux Id: GH-6903
The compiler will now inline calls to maps:get/3.
Own Id: OTP-18502
In Erlang/OTP 27, 0.0 will no longer be considered to be exactly equal to -0.0. See Upcoming Potential Incompatibilities.
Own Id: OTP-18574

Compiler 8.2.6.4

Fixed Bugs and Malfunctions

In rare circumstances, an unsafe optimization could cause the compiler to generate incorrect code for list matching.
Own Id: OTP-19003 Aux Id: GH-8187, PR-8189
In rare circumstances, the compiler code generate unsafe code for a bit syntax match.
Own Id: OTP-19019

Compiler 8.2.6.3

Fixed Bugs and Malfunctions

Fixed a bug that could cause the stack trace of throw exceptions to be erroneously optimized out.
Own Id: OTP-18626 Aux Id: GH-7356

Compiler 8.2.6.2

Fixed Bugs and Malfunctions

The compiler could be very slow when compiling guards with multiple guard tests separated with 'or' or ';'.
Own Id: OTP-18617 Aux Id: GH-7338

Compiler 8.2.6.1

Fixed Bugs and Malfunctions

Fixed a bug where a failing bsl expression in a guard threw an exception instead of causing the guard to fail.
Own Id: OTP-18576
Complex guard expression using the or operator and guard BIFs that can fail could sometimes be miscompiled so that the guard would succeed even if a call to a guard BIF failed.
Own Id: OTP-18593 Aux Id: GH-7252

Compiler 8.2.6

Fixed Bugs and Malfunctions

Fixed type handling bugs that could cause an internal error in the compiler for correct code.
Own Id: OTP-18565 Aux Id: GH-7147

Compiler 8.2.5

Fixed Bugs and Malfunctions

When a map update such as #{}#{key:=value} that should fail with an exception was unused, the exception would be lost.
Own Id: OTP-18497 Aux Id: GH-6960, PR-6965
Fixed bug in the validator that made it reject valid code.
Own Id: OTP-18516 Aux Id: GH-6969

Compiler 8.2.4

Fixed Bugs and Malfunctions

Fixed a bug that would cause the compiler to hang.
Own Id: OTP-18378 Aux Id: GH-6604
Fixed a crash when compiling code that contained maybe expressions.
Own Id: OTP-18381 Aux Id: GH-6601
Constructing a binary with an explicit size of all for a binary segment would crash the compiler.
Own Id: OTP-18407 Aux Id: GH-6707
The compiler would generate incorrect code for the following type of expression:
Pattern = BoundVar1 = . . . = BoundVarN = Expression
An exception should be raised if any of the bound variables have different values than Expression. The compiler would generate code that would cause the bound variables to be bound to the value of Expressionwhether the value matched or not.
Own Id: OTP-18470 Aux Id: GH-6873, PR-6877

Compiler 8.2.3

Fixed Bugs and Malfunctions

Fixed a bug that could cause legal code to fail validation.
Own Id: OTP-18365
Eliminated a rare crash in the beam_types module.
Own Id: OTP-18368

Compiler 8.2.2

Fixed Bugs and Malfunctions

Line number in compiler messages would be truncated to 4 digits for line numbers greater than 9999.
Own Id: OTP-18268 Aux Id: GH-6332
In rare circumstance, matching a binary as part of a receive clause could cause the compiler to terminate because of an internal consistency check failure.
Own Id: OTP-18273 Aux Id: GH-6341
Compiling a function with complex bit syntax matching such as f(<<X:0, _:X>>, <<Y:0, _:Y>>) -> ok. could crash the compiler.
Own Id: OTP-18308 Aux Id: GH-6426
It is not allowed to call functions from guards. The compiler failed to reject a call in a guard when done by constructing a record with a default initialization expression that called a function.
Own Id: OTP-18325 Aux Id: GH-6465, GH-6466
The compiler could crash when using a record with complex field initialization expression as a filter in a list comprehension.
Own Id: OTP-18336 Aux Id: GH-6501, PR-6502

Compiler 8.2.1

Fixed Bugs and Malfunctions

The compiler will now forbid using the empty atom '' as module name. Also forbidden are modules names containing control characters, and module names containing only spaces and soft hyphens.
Own Id: OTP-18125 Aux Id: GH-6026
The bin_opt_info and recv_opt_info options would cause the compiler to crash when attempting to compile generated code without location information.
Own Id: OTP-18162 Aux Id: PR-6102
In rare circumstances involving floating point operations, the compiler could terminate with an internal consistency check failure.
Own Id: OTP-18182 Aux Id: GH-6163
In rare circumstances when doing arithmetic instructions on non-numbers, the compiler could crash.
Own Id: OTP-18183 Aux Id: GH-6169
In rare circumstances, complex boolean expressions in nested cases could cause the compiler to crash.
Own Id: OTP-18184 Aux Id: GH-6164
Expression similar to #{assoc:=V} = #key=>self()}, V would return the empty map instead of raising an exception.
Own Id: OTP-18186
Eliminated a crash in the beam_ssa_bool pass of the compiler when compiling a complex guard expression.
Own Id: OTP-18187 Aux Id: GH-6184
In rare circumstances, the compiler could crash with an internal consistency check failure.
Own Id: OTP-18202 Aux Id: GH-6222
When compiling with the option inline_list_funcs, the compiler could produce a nonsensical warning.
Own Id: OTP-18214 Aux Id: GH-6158
When given the no_ssa_opt option, the compiler could terminate with an internal consistency failure diagnostic when compiling map matching.
Own Id: OTP-18234 Aux Id: GH-6277

Improvements and New Features

Made warnings for existing atoms being keywords in experimental features more precise, by not warning about quoted atoms.
Own Id: OTP-18050
There is a new configure option, --enable-deterministic-build, which will apply the deterministic compiler option when building Erlang/OTP. The deterministic option has been improved to eliminate more sources of non-determinism in several applications.
Own Id: OTP-18165 Aux Id: PR-5965

Compiler 8.2

Fixed Bugs and Malfunctions

A subtle bug regarding variable scoping has been corrected. Consider this example:
(A=1) + fun() -> A = 2() end
In the shell, the expression correctly evaluates to 3. In compiled code, it raised a {badmatch, 2} exception.
Own Id: OTP-17810 Aux Id: GH-5379
Fixed a rare bug that would crash the compiler during type optimization.
Own Id: OTP-17820
Starting in OTP 24, when a fun was created and immediately used, it would be inlined. An unintended consequence of the inlining was that what would be a function_clause exception without the inlining would now be a rather confusing case_clause exception. This has been corrected, so that function_clause exceptions remain function_clause exceptions in inlined code.
Own Id: OTP-17860 Aux Id: GH-5513, OTP-17226
If a default record field initialization (_ = Expr) was used even though all records fields were explicitly initialized, Expr would not be evaluated. That would not be a problem, except when Expr would bind a variable subsequently used, in which case the compiler would crash.
As an example, if record #r{} is defined to have only one field a, the following code would crash the compiler:
#r{a=[],_=V=42}, V
To fix that problem, the compiler will make sure that Expr is always evaluated at least once. The compiler will now rewrite the example to essentially:
V=42, #r{a=[]}, V
Own Id: OTP-18083

Improvements and New Features

To enable more optimizations, BEAM files compiled with OTP 21 and earlier cannot be loaded in OTP 25.
Own Id: OTP-16702
Added support for the compile attribute -nifs() to empower compiler and loader with information about which functions may be overridden as NIFs by erlang:load_nif/2. It is recommended to use this attribute in all modules that load NIF libraries.
Own Id: OTP-17151 Aux Id: ERIERL-590, PR-5479
When binary construction using the binary syntax fails, the error message printed in the shell and by erl_error:format_exception/3,4 will contain more detailed information about what went wrong.
Own Id: OTP-17504 Aux Id: GH-4971, PR-5281, PR-5752
The Erlang compiler now includes type information in BEAM files, and the JIT can now use that type information to do optimizations such as eliminating or simplifying type tests.
Own Id: OTP-17684 Aux Id: PR-5316, PR-5664
Improved the JIT's support for external tools like perf and gdb, allowing them to show line numbers and even the original Erlang source code when that can be found.
To aid them in finding the source code, the absolute_path compiler option has been added to embed the absolute file path of a module.
Own Id: OTP-17685
The maybe ... end construction proposed in EEP-49 has been implemented. It can simplify complex code where otherwise deeply nested cases would have to be used.
To enable maybe, give the option -enable-feature maybe_expr to erlc or add -feature(maybe_expr, enable). inside the module.
Own Id: OTP-17705 Aux Id: PR-5411
When a record matching or record update fails, a {badrecord,ExpectedRecordTag} exception used to be raised. In this release, the exception has been changed to {badrecord,ActualValue}, where ActualValue is the actual that was found instead of the expected record.
Own Id: OTP-17841 Aux Id: PR-5694
Improved optimization of try/catch expressions.
Own Id: OTP-17842
The beam_trim pass of the compiler could be extremely slow for huge straight-line functions. It will now compile such functions much faster (down to seconds from minutes for some huge functions).
Own Id: OTP-17885 Aux Id: GH-5140
Added support for configurable features as described in EEP-60. Features can be enabled/disabled during compilation with options (-enable-feature Feature, -disable-feature Feature and +{feature, Feature, enable|disable}) to erlc as well as with directives (-feature(Feature, enable|disable).) in the file. Similar options can be used to erl for enabling/disabling features allowed at runtime. The new maybe expression (EEP-49) is fully supported as the feature maybe_expr. The features support is documented in the reference manual.
Own Id: OTP-17988

Compiler 8.1.1.6

Fixed Bugs and Malfunctions

In rare circumstances, an unsafe optimization could cause the compiler to generate incorrect code for list matching.
Own Id: OTP-19003 Aux Id: GH-8187, PR-8189
In rare circumstances, the compiler code generate unsafe code for a bit syntax match.
Own Id: OTP-19019

Compiler 8.1.1.5

Fixed Bugs and Malfunctions

The compiler could be very slow when compiling guards with multiple guard tests separated with 'or' or ';'.
Own Id: OTP-18617 Aux Id: GH-7338

Compiler 8.1.1.4

Fixed Bugs and Malfunctions

Complex guard expression using the or operator and guard BIFs that can fail could sometimes be miscompiled so that the guard would succeed even if a call to a guard BIF failed.
Own Id: OTP-18593 Aux Id: GH-7252

Compiler 8.1.1.3

Fixed Bugs and Malfunctions

The compiler would generate incorrect code for the following type of expression:
Pattern = BoundVar1 = . . . = BoundVarN = Expression
An exception should be raised if any of the bound variables have different values than Expression. The compiler would generate code that would cause the bound variables to be bound to the value of Expressionwhether the value matched or not.
Own Id: OTP-18470 Aux Id: GH-6873, PR-6877

Compiler 8.1.1.2

Fixed Bugs and Malfunctions

It is not allowed to call functions from guards. The compiler failed to reject a call in a guard when done by constructing a record with a default initialization expression that called a function.
Own Id: OTP-18325 Aux Id: GH-6465, GH-6466
Fixed a bug that could cause legal code to fail validation.
Own Id: OTP-18365

Compiler 8.1.1.1

Fixed Bugs and Malfunctions

The bin_opt_info and recv_opt_info options would cause the compiler to crash when attempting to compile generated code without location information.
Own Id: OTP-18162 Aux Id: PR-6102
In rare circumstances involving floating point operations, the compiler could terminate with an internal consistency check failure.
Own Id: OTP-18182 Aux Id: GH-6163

Compiler 8.1.1

Fixed Bugs and Malfunctions

Fixed a performance bug in the validator that made certain files take a very long time to compile.
Own Id: OTP-18066 Aux Id: GH-5915
In rare circumstances, the compiler would mistakenly assume that a call to setelement/3 would always fail and remove all code following the call.
Own Id: OTP-18082

Compiler 8.1

Fixed Bugs and Malfunctions

The expression <<0/native-float>>=Bin would always fail to match, while <<0/float-native>>=Bin would match (provided that Bin contained the binary representation of 0.0)
Own Id: OTP-17895

Improvements and New Features

The compiler will now compile huge functions with straight-line code faster.
Own Id: OTP-17886 Aux Id: GH-5140, GH-5686

Compiler 8.0.4

Fixed Bugs and Malfunctions

When the compiler is invoked by Dialyzer, it will no longer apply an optimization of binary patterns that would turn the pattern <<"bar">> into <<6447474:24>>, which would be very confusing when printed out by Dialyzer.
Own Id: OTP-17768 Aux Id: GH-5429
The compiler would replace known failing calls (such as atom_to_list(42)) with a call to error(badarg). With the extended error information introduced in OTP 24 (EEP 54), those "optimized" calls would not have extended error information. To ensure that as much extended error information as possible is available, the compiler now keeps the original call even when it is known to fail.
Own Id: OTP-17786 Aux Id: GH-5440

Compiler 8.0.3

Fixed Bugs and Malfunctions

If a parse transform raised an exception using throw/1 or exit/1, the compiler would report that as an internal compiler error, which would be confusing. Amended to report that the parse transform failed.
Own Id: OTP-17421
The failing call io:format("~p\n") would result in a warning for line number 0 instead of the correct line and column numbers. This has been corrected, and all warnings for failing calls to io:format() has been rephrased to make it clearer exactly what the problem is.
Own Id: OTP-17430
When the options warn_missing_spec and export_all were given, there would only be warnings for missing specs for functions that had been explicitly exported using an -export attribute.
Own Id: OTP-17434 Aux Id: GH-4772
In rare circumstances, the compiler could emit an incorrect warning for a term that was constructed but never used.
Own Id: OTP-17446 Aux Id: PR-4899
Corrected bugs where builds were not reducible even when the deterministic option was given. In particular, modules with map literals with more than 32 elements could cause this problem.
As part of this fix, the term_to_binary BIF now accepts the option deterministic.
Own Id: OTP-17495 Aux Id: PR-5153
The MODULE and MODULE_STRING macros would always appear to be defined (when tested by -ifdef), even though no -module() declaration had been seen yet. Changed so that -ifdef ?MODULE. will not consider ?MODULE defined if -module() has not been previously seen.
Own Id: OTP-17505 Aux Id: GH-4995
In a guard, not (X =:= true) would incorrectly evaluate to false for non-boolean values of X.
Own Id: OTP-17510 Aux Id: GH-5007
When the deterministic option was given to the compiler, the ?FILE macro would be expanded to full path of the source file before the first include directive and to base part of the filename after include directive.
Own Id: OTP-17581 Aux Id: PR-5141

Compiler 8.0.2

Fixed Bugs and Malfunctions

A compiler optimization pass could crash when given odd but legal code using throw/1.
Own Id: OTP-17489 Aux Id: GH-4953

Compiler 8.0.1

Fixed Bugs and Malfunctions

Fixed a bug that could cause after blocks to be ignored when erlang:raise/3 was used in a catch block.
Own Id: OTP-17428 Aux Id: GH-4859
Fixed a bug in the validation pass that could cause it to reject valid code.
Own Id: OTP-17437 Aux Id: OTP-17357, GH-4774

Compiler 8.0

Fixed Bugs and Malfunctions

A floating point zero (0.0) can be both positive (+0.0) and negative (-0.0). Multiple bugs in the compiler, runtime system, and STDLIB have been fixed to ensure that the minus sign on 0.0 is not lost.
Own Id: OTP-17077 Aux Id: ERL-1431, PR-2903, PR-2905, PR-2906
A repeated stack trace variable in a try/catch was not rejected. The following example will now cause a compilation error:
```
try E catch _:A:A -> A
      end.
```
Own Id: OTP-17104 Aux Id: ERL-1380
Eliminated a Dialyzer crashed when the -MMD option is used to generate a dependency file and a BEAM file a the same time.
Own Id: OTP-17118 Aux Id: PR-2825
When the makedep option was given, the compiler would crash if the dependency output contained non-latin1 characters. The compiler will now output the dependency information encoded in UTF-8 to avoid crashing.
Own Id: OTP-17206

Improvements and New Features

Selective receive optimization will now be applied much more often.
The new recv_opt_info compile flag can be used to print diagnostics relating to this optimization.
You can read more about the selective receive optimization in the Efficiency Guide.
Own Id: OTP-10391 Aux Id: OTP-16226
erlang:throw/1 will no longer build stack traces when we can prove that they will never be inspected.
Own Id: OTP-16334
Variables bound between the keywords 'try' and 'of' can now be used in the clauses following the 'of' keyword (that is, in the success case when no exception was raised).
Own Id: OTP-16706 Aux Id: ERL-1281
Compiler warnings and errors now include column numbers in addition to line numbers.
When a compiler message is emitted, the source line is printed along with a marker (a ^ character) that indicates the column position of the issue. The option 'brief' removes the printout of the source line.
The compiler option {error_location, line | column} has been added. The default value is column. Besides adding column numbers to compilation warnings and errors, the option also determines whether column numbers are included in abstract code. If tools stop working, setting the environment variable ERL_COMPILER_OPTIONS can help (include {error_location, line}).
The compiler will now call the function PT:parse_transform_info/0 in parse transforms (if it exists). It can be used by parse transforms to signal that they can only handle line numbers in abstract code.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-16824 Aux Id: PR-2664, PR-3006
Fixed a performance bug that made functions with lots of try/after blocks slow to compile.
Own Id: OTP-16867 Aux Id: ERL-1354
The experimental HiPE application has been removed, together with all related functionality in other applications.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-16963
Generators in list and binary comprehensions will now raise a {bad_generator,Generator} exception if the generator has an incorrect type (instead of raising an ad-hoc badarg or badarih exception). Similarly, when a filter does not evaluate to a boolean, a {bad_filter,Filter} exception will be raised. Some minor bugs in the compilation of binary comprehensions have also been fixed.
Own Id: OTP-16964
Some compiler warnings, such as the warning for an expression whose result is ignored, could not be suppressed by assigning to a variable beginning with '_', but only by assigning to the anonymous variable ('_'). This has now been changed so that any warning that can be suppressed by assigning to the anonymous variable can also be suppressed by assigning to a variable beginning with '_'.
Own Id: OTP-16981 Aux Id: ERL-1113
The previously undocumented compiler options warn_missing_spec and warn_missing_spec_all are now documented.
Own Id: OTP-17078 Aux Id: ERL-1430, PR-2918
The compiler will now emit warnings when (previously bound) underscore-prefixed variables are matched.
Own Id: OTP-17123
Erlang source files not encoded in utf-8 will no longer be accepted by the compiler unless it contains a "coding: latin-1" comment.
Own Id: OTP-17168
New compiler options from_abstr and no_lint have been added. They are useful when implementing other languages running on the BEAM.
Own Id: OTP-17172
The bit matching and construction syntax now supports 16-bit floats (IEEE 754-2008).
Own Id: OTP-17207
The compiler will now inline funs that are used only once immediately after their definition.
Own Id: OTP-17226 Aux Id: GH-4019, PR-4545
It is now possible to disable warnings emitted from the compiler's optimization passes with the new options nowarn_opportunistic, nowarn_nomatch, nowarn_ignored, and nowarn_failed.
Own Id: OTP-17260
Introduce new types nonempty_binary/0 and nonempty_bitstring/0.
Own Id: OTP-17301 Aux Id: GH-4636
Add compiler option {nowarn_unused_record, RecordNames}. Document compiler option nowarn_unused_type.
Own Id: OTP-17330

Compiler 7.6.9.3

Fixed Bugs and Malfunctions

It is not allowed to call functions from guards. The compiler failed to reject a call in a guard when done by constructing a record with a default initialization expression that called a function.
Own Id: OTP-18325 Aux Id: GH-6465, GH-6466
Fixed a bug that could cause legal code to fail validation.
Own Id: OTP-18365
The compiler would generate incorrect code for the following type of expression:
Pattern = BoundVar1 = . . . = BoundVarN = Expression
An exception should be raised if any of the bound variables have different values than Expression. The compiler would generate code that would cause the bound variables to be bound to the value of Expressionwhether the value matched or not.
Own Id: OTP-18470 Aux Id: GH-6873, PR-6877

Compiler 7.6.9.2

Fixed Bugs and Malfunctions

In rare circumstances, the compiler would mistakenly assume that a call to setelement/3 would always fail and remove all code following the call.
Own Id: OTP-18082

Compiler 7.6.9.1

Fixed Bugs and Malfunctions

Fixed a bug in the validation pass that could cause it to reject valid code.
Own Id: OTP-17437 Aux Id: OTP-17357, GH-4774

Compiler 7.6.9

Fixed Bugs and Malfunctions

Reverted the fix for OTP-17357 as it turned out to be incomplete and made the validator reject much more legal code than before.
It will be fixed more thoroughly in a later patch.
Own Id: OTP-17386 Aux Id: ERIERL-650, OTP-17357

Compiler 7.6.8

Fixed Bugs and Malfunctions

Fixed a bug in the validator that could cause it to reject valid code.
Own Id: OTP-17357 Aux Id: GH-4774

Compiler 7.6.7

Fixed Bugs and Malfunctions

Fixed a bug in the type optimization pass that could yield incorrect values or cause the wrong clauses to be executed.
Own Id: OTP-17073
Fixed a bug in the validator that could cause it to reject valid code.
Own Id: OTP-17126 Aux Id: ERL-1471

Compiler 7.6.6

Fixed Bugs and Malfunctions

Several minor compiler bugs have been fixed:
Constructing a binary with a list as a size of a binary segment could generate a BEAM file that could not be loaded.
When matching a binary segment of type float and ignoring the matched out value, the match would always succeed, even if the size was invalid or the value of the float was NaN or some other non-numeric float value.
Attempting to construct an invalid external fun (e.g. fun m:f:bad) is supposed to raise a 'badarg' exception, but if the value was never used, no exception would be raised.
Own Id: OTP-16932
Fixed multiple bugs in the validator that could cause it to reject valid code.
Own Id: OTP-17039 Aux Id: ERL-1426
The compiler could crash when a binary comprehension had a generator that depended on another generator.
Own Id: OTP-17045 Aux Id: ERL-1427
Fixed a bug in the type optimization pass that could yield incorrect values or cause the wrong clauses to be executed.
Own Id: OTP-17072 Aux Id: ERL-1440

Compiler 7.6.5

Fixed Bugs and Malfunctions

Fixed a bug in the boolean optimization pass that caused the compiler to confuse different clauses.
Own Id: OTP-16951 Aux Id: ERL-1384

Compiler 7.6.4

Fixed Bugs and Malfunctions

Fixed a performance bug that could be triggered by tuple matching in very large functions.
Own Id: OTP-16895 Aux Id: ERL-1359

Compiler 7.6.3

Fixed Bugs and Malfunctions

If the update of a map with the 'Map#{Key := Value}' syntax failed, the line number in the stack backtrace could be incorrect.
Own Id: OTP-16701 Aux Id: ERL-1271
Fixed a performance bug that slowed down compilation of modules with deeply nested terms.
Own Id: OTP-16755 Aux Id: ERL-1297
The compiler could in rare circumstances do an an unsafe optimization that would result in a matching of a nested map pattern would fail to match.
Own Id: OTP-16820
Fixed a bug in the validator that caused it to reject valid code.
Own Id: OTP-16838 Aux Id: ERL-1340

Compiler 7.6.2

Fixed Bugs and Malfunctions

When calls to is_map_key were repeated, the compiler could terminate with an internal consistency failure.
Own Id: OTP-16708 Aux Id: ERL-1276
Fixed a bug in the type inference pass that could cause the compiler to hang.
Own Id: OTP-16745 Aux Id: ERL-1289

Compiler 7.6.1

Fixed Bugs and Malfunctions

In rare circumstances, a guard using 'not' could evaluate to the wrong boolean value.
Own Id: OTP-16652 Aux Id: ERL-1246
A guard expression that referenced a variable bound to a boolean expression could evaluate to the wrong value.
Own Id: OTP-16657 Aux Id: ERL-1253

Compiler 7.6

Fixed Bugs and Malfunctions

erlang:fun_info(fun foo/1, name/1) used to return a function name based on the name of the function that fun foo/1 was used in. The name returned is now -fun.foo/1-.
Own Id: OTP-15837
Initialization of record fields using _ is no longer allowed if the number of affected fields is zero.
Own Id: OTP-16516

Improvements and New Features

EEP-52 has been implemented.
In binary matching, the size of the segment to be matched is now allowed to be a guard expression, and similarly in map matching the keys can now be guard expressions. See the Erlang Reference Manual and Programming Examples for more details.
Language compilers or code generators that generate Core Erlang code may need to be updated to be compatible with the compiler in OTP 23. For more details, see the section Backwards Compatibility in EEP 52.
Own Id: OTP-14708
Allow underscores in numeric literals to improve readability. Examples: 123_456_789, 16#1234_ABCD.
Own Id: OTP-16007 Aux Id: PR-2324
Improved the type optimization pass' inference of types that depend on themselves, giving us more accurate types and letting us track the content types of lists.
Own Id: OTP-16214 Aux Id: PR-2460
Support message queue optimization also for references returned from the new spawn_request() BIFs.
Own Id: OTP-16367 Aux Id: OTP-15251
The compiler will now raise a warning when inlining is used in modules that load NIFs.
Own Id: OTP-16429 Aux Id: ERL-303
Refactored the internal handling of deprecated and removed functions.
Own Id: OTP-16469
Line information was sometimes incorrect for floating-point math exceptions.
Own Id: OTP-16505 Aux Id: ERL-1178
The debug_info option can now be specified in -compile() attributes.
Own Id: OTP-16523 Aux Id: ERL-1058
Reduced the resource usage of erlc in parallel builds (e.g. make -j128).
Own Id: OTP-16543 Aux Id: ERL-1186

Compiler 7.5.4.3

Improvements and New Features

Fixed a bug in the type optimization pass that could yield incorrect values or cause the wrong clauses to be executed.
Own Id: OTP-17073

Compiler 7.5.4.2

Fixed Bugs and Malfunctions

Fixed a bug in the validator that could cause it to reject valid code
Own Id: OTP-17039 Aux Id: ERL-1426

Compiler 7.5.4.1

Fixed Bugs and Malfunctions

Fixed a bug that could cause the compiler to crash on code that constructed binaries.
Own Id: OTP-16747 Aux Id: ERL-1290

Compiler 7.5.4

Fixed Bugs and Malfunctions

Fixed a bug in the validator that could cause it to reject valid code.
Own Id: OTP-16580 Aux Id: ERL-1212

Compiler 7.5.3

Fixed Bugs and Malfunctions

A 'receive' with an 'after 0' clause would prevent the optimization that can avoid scanning the entire receive queue when matching on a newly created reference.
Own Id: OTP-16350
HiPE can again handle modules with catch and try constructs.
Own Id: OTP-16418
Fixed a bug in bit-syntax optimization that could crash the compiler.
Own Id: OTP-16515

Compiler 7.5.2

Fixed Bugs and Malfunctions

Fixed a bug that could cause the compiler to reject valid code that used the is_map_key/2 BIF.
Own Id: OTP-16452 Aux Id: ERL-1161
Fixed a bug that could cause the compiler to reject valid code that matched the same map key several times.
Own Id: OTP-16456 Aux Id: ERL-1163
The compiler could crash when compiling a convoluted receive statement.
Own Id: OTP-16466 Aux Id: ERL-1170
The compiler could crash when a fun was created but never used.
The compiler could crash when compiling the expression true = 0 / X.
Own Id: OTP-16467 Aux Id: ERL-1166, ERL-1167

Compiler 7.5.1

Fixed Bugs and Malfunctions

Fixed a bug in the compiler that could cause it to reject valid code.
Own Id: OTP-16385 Aux Id: ERL-1128

Compiler 7.5

Fixed Bugs and Malfunctions

Fixed a bug in the linter where list and binary comprehensions could suppress unsafe variable errors.
Own Id: OTP-16053 Aux Id: ERL-1039
When a compilation starts from Core Erlang code, the core_lint pass will always be run and the compilation will be aborted if any errors are found.
Own Id: OTP-16181 Aux Id: ERL-1065

Improvements and New Features

The warning message that appears when the compiler detects a non-utf-8 encoded source file without an encoding string in the beginning of the file has been changed to contain information about that support for latin1 encoded source files without an encoding string will be removed in Erlang/OTP 24.
Own Id: OTP-16054 Aux Id: OTP-11791

Compiler 7.4.9

Fixed Bugs and Malfunctions

Fixed a performance bug that caused repeated matches of large records to take a very long time to compile.
Own Id: OTP-16259 Aux Id: ERIERL-436

Compiler 7.4.8

Fixed Bugs and Malfunctions

The compiler could do an unsafe optimization of receives, which would cause a receive to only scan part of the message queue.
This bug fix in the compiler fixes a bug in the socket module.
Own Id: OTP-16219 Aux Id: ERL-1076

Compiler 7.4.7

Fixed Bugs and Malfunctions

Fixed a bug where the compiler could generate incorrect code for a 'receive' statement inside a 'try'.
Own Id: OTP-16199

Compiler 7.4.6

Fixed Bugs and Malfunctions

Fixed a bug in the bit-syntax optimization pass that could crash the compiler.
Own Id: OTP-16103 Aux Id: ERL-1050

Compiler 7.4.5

Fixed Bugs and Malfunctions

Code such as the following would crash the compiler in OTP 22: [some_atom = fun some_function/1]
Own Id: OTP-15833
Compilation could get really slow (in the order of minutes instead of seconds) when compiling huge functions. (Thanks to Kostis Sagonas for reporting this bug.)
Own Id: OTP-15923
Fixed a bug in the validator that could reject valid code.
Own Id: OTP-15954 Aux Id: ERL-995
In rare circumstances, when two clauses had identical bodies and guard tests that tested a single boolean variable, the guard test for the second clause could be discarded, executing the second clause unconditionally if the first clause was not executed.
Own Id: OTP-15963
Fixed extremely slow compilation for huge functions doing predominantly pattern matching.
Own Id: OTP-15966 Aux Id: ERL-1014
The compiler could generate unsafe code (that would crash the runtime system) for map pattern matching. The code could be unsafe if the matched key was not present in the map at runtime.
Own Id: OTP-15968 Aux Id: ERL-1017
Correct code using try/after could fail to compile when using the option 'no_type_opt'.
Own Id: OTP-15969 Aux Id: ERL-997
The compiler could crash when compiling code that called 'length/1' on a binary extracted using the binary syntax.
Own Id: OTP-15970 Aux Id: ERL-1013
Fixed a bug where the compiler could fail with an internal consistency failure error when compiling receive statements.
Own Id: OTP-15982 Aux Id: ERL-1022
Fixed a problem where the compiler would crash when compiling binary matching in a function head.
Own Id: OTP-15985 Aux Id: ERL-1026

Compiler 7.4.4

Fixed Bugs and Malfunctions

Fixed a compiler crash introduced in 22.0.6 (OTP-15952).
Own Id: OTP-15953 Aux Id: ERL-999

Compiler 7.4.3

Fixed Bugs and Malfunctions

Fixed an unsafe optimization when matching tuple_size/1 outside of guards, which could crash the emulator if the argument was not a tuple.
Own Id: OTP-15945
Fixed a rare bug that could cause the wrong kind of exception to be thrown when a BIF failed in a function that matched bitstrings.
Own Id: OTP-15946
Fixed a bug where receive statements inside try/catch blocks could return incorrect results.
Own Id: OTP-15952

Compiler 7.4.2

Fixed Bugs and Malfunctions

Fixed an incorrect type determination for constructed binaries, which could cause is_binary checks to succeed when they shouldn't have.
Own Id: OTP-15872

Compiler 7.4.1

Fixed Bugs and Malfunctions

The type optimization pass of the compiler could hang or loop for a long time when analyzing a setelement/3 call with a variable position.
Own Id: OTP-15828 Aux Id: ERL-948
Certain complex receive statements would result in an internal compiler failure.
Own Id: OTP-15832 Aux Id: ERL-950
Fixed an unsafe type optimization.
Own Id: OTP-15838
Fixed a crash when optimizing compiler-generated exceptions (like badmatch) whose offending term was a constructed binary.
Own Id: OTP-15839 Aux Id: ERL-954
Fixed a bad optimization related to the ++/2 operator, where the compiler assumed that it always produced a list ([] ++ RHS returns RHS verbatim, even if it's not a list).
Own Id: OTP-15841
An is_binary/1 test followed by is_bitstring/1 (or vice versa) could fail because of an usafe optimization.
Own Id: OTP-15845
A Core Erlang module where the last clause in a case matched a map would fail to load.
Own Id: OTP-15846 Aux Id: ERL-955
Fixed a bug that could cause the compiler to crash when compiling complex nested case expressions.
Own Id: OTP-15848 Aux Id: ERL-956

Compiler 7.4

Fixed Bugs and Malfunctions

record_info/2 is a pseudo-function that requires literal arguments known at compile time. Therefore, the following usage is illegal: fun record/info/2. The compiler would crash when during compilation of that kind of code. Corrected to issue a compilation error.
Own Id: OTP-15760 Aux Id: ERL-907

Improvements and New Features

The compiler has been rewritten to internally use an intermediate representation based on Static Single Assignment (SSA). The new intermediate representation makes more optimizations possible.
Most noticeable is that the binary matching optimizations are now applicable in many more circumstances than before.
Another noticeable change is that type optimizations are now applied across local function calls, and will remove a lot more redundant type tests than before.
Own Id: OTP-14894 Aux Id: ERL-714
Funs are no longer created when they are only used locally, greatly improving the performance of named funs and "fun-wrapped" macros.
Own Id: OTP-15273 Aux Id: ERL-639
All compiler options that can be given in the source file can now also be given in the option list or from the command line for erlc.
Specifically, the option {nowarn_deprecated_function,MFAs} was only recognized when given in the file with the attribute -compile(). The option {nowarn_unused_function,FAs} was incorrectly documented to only work in a file, but it also worked when given in the option list.
Own Id: OTP-15456
Do not allow function specifications for functions residing in other modules.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-15563 Aux Id: ERL-845, OTP-15562
Internal documentation has now been added to the Erts and Compiler applications.
The internal documents for Erts describe miscellaneous interesting implementation details. Those details can change at any time.
The internal documentation for Compiler documents the API for the Core Erlang modules. While we will not change those APIs without good reason, we don't give the same guarantees about backward compatibility as for the rest of the APIs in OTP.
Own Id: OTP-15715
There are new compiler options nowarn_removed and {nowarn_removed,Items} to suppress warnings for functions and modules that have been removed from OTP.
Own Id: OTP-15749 Aux Id: ERL-904

Compiler 7.3.2

Fixed Bugs and Malfunctions

An expression such as (A / B) band 16#ff would crash the compiler.
Own Id: OTP-15518 Aux Id: ERL-829
There could be an incorrect warning when the tuple_calls option was given. The generated code would be correct. Here is an example of code that would trigger the warning:
(list_to_atom("prefix_" ++ atom_to_list(suffix))):doit(X).
Own Id: OTP-15552 Aux Id: ERL-838
Optimize (again) Dialyzer's handling of left-associative use of andalso and orelse in guards.
Own Id: OTP-15577 Aux Id: ERL-851, PR-2141, PR-1944

Compiler 7.3.1

Fixed Bugs and Malfunctions

An optimization that avoided allocation of a stack frame for some case expressions was introduced in OTP 21. (ERL-504/OTP-14808) It turns out that in rare circumstances, this optimization is not safe. Therefore, this optimization has been disabled.
A similar optimization will be included in OTP 22 in a safe way.
Own Id: OTP-15501 Aux Id: ERL-807, ERL-514, OTP-14808

Compiler 7.3

Fixed Bugs and Malfunctions

Fixed a rare internal consistency failure caused by a bug in the beam_jump pass. (Thanks to Simon Cornish for reporting this bug.)
Own Id: OTP-15400 Aux Id: ERL-759
The compiler could fail with an internal consistency check failure when compiling code that used the is_function/2 BIF.
Own Id: OTP-15435 Aux Id: ERL-778
When an external fun was used, warnings for unused variables could be suppressed.
Own Id: OTP-15437 Aux Id: ERL-762
The compiler would crash when compiling an after block that called erlang:raise/3 like this: erlang:raise(Class, Stacktrace, Stacktrace)
Own Id: OTP-15481

Improvements and New Features

When specified, the +{source,Name} option will now override the actual file name in stack traces, instead of only affecting the return value of Mod:module_info().
The +deterministic flag will also affect stack traces now, omitting all path information except the file name, fixing a long-standing issue where deterministic builds required deterministic paths.
Own Id: OTP-15245 Aux Id: ERL-706

Compiler 7.2.7

Fixed Bugs and Malfunctions

Fixed a bug where incorrect code was generated following a binary match guard.
Own Id: OTP-15353 Aux Id: ERL-753

Compiler 7.2.6

Fixed Bugs and Malfunctions

In rare circumstances, the matched out tail of a binary could be the entire original binary. (There was partial correction to this problem in version 7.2.5 of the compiler application.)
Own Id: OTP-15335 Aux Id: ERL-689, OTP-15219

Compiler 7.2.5

Fixed Bugs and Malfunctions

Fixed a bug that prevented certain variable-sized binary comprehensions from compiling.
Own Id: OTP-15186 Aux Id: ERL-665
When compiling from Core Erlang, funs created in certain expressions that were only used for their side-effects were subtly broken.
Own Id: OTP-15188 Aux Id: ERL-658
There could be an internal consistency failure when a receive was nested in a try/catch.
Own Id: OTP-15218 Aux Id: ERL-684
In rare circumstances, the matched out tail of a binary could be the entire original binary.
Own Id: OTP-15219 Aux Id: ERL-689
When is_map_key/2 was used in a guard together with the not/1 or or/2 operators, the error behavior could be wrong when is_map_key/2 was passed a non-map as the second argument.
In rare circumstances, compiling code that uses is_map_key/2 could cause an internal consistency check failure.
Own Id: OTP-15227 Aux Id: ERL-699
The compiler could crash when compiling a function with multiple receives in multiple clauses.
Own Id: OTP-15235 Aux Id: ERL-703

Compiler 7.2.4

Fixed Bugs and Malfunctions

Fix a regression in OTP-15204 that removed .beam file metadata that some external build tools relied on.
Own Id: OTP-15292

Compiler 7.2.3

Fixed Bugs and Malfunctions

Fixed an issue where files compiled with the +deterministic option differed if they were compiled in a different directory but were otherwise identical.
Own Id: OTP-15204 Aux Id: ERL-679

Compiler 7.2.2

Fixed Bugs and Malfunctions

In rare cases involving matching of binary literal strings, the compiler could optimize away code that should be executed.
Own Id: OTP-15156 Aux Id: ERL-655
There could be an internal consistency check failure when compiling code that called map_get(Key, Map) and then updated the same map.
Own Id: OTP-15157
In rare circumstances, the compiler could crash in beam_jump when compiling a floating point operation.
Own Id: OTP-15166 Aux Id: ERL-660

Compiler 7.2.1

Fixed Bugs and Malfunctions

The could could crash when compiling a complicated function that used the binary syntax.
Own Id: OTP-15150 Aux Id: ERL-650

Compiler 7.2

Fixed Bugs and Malfunctions

Fixed an error in an optimization pass that caused impossible tuple matching.
Own Id: OTP-14855 Aux Id: ERL-549
The exception thrown when a list comprehension was given a non-list term was not always correct.
Own Id: OTP-14992 Aux Id: ERL-572
The compiler could produce incorrect code in rare circumstances when the [{inline,F/A}] option was used.
Own Id: OTP-15115 Aux Id: PR-1831

Improvements and New Features

Changed the default behaviour of .erlang loading: .erlang is no longer loaded from the current directory. c:erlangrc(PathList) can be used to search and load an .erlang file from user specified directories.
escript, erlc, dialyzer and typer no longer load an .erlang at all.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-14439
Support for "tuple calls" have been removed from the run-time system. Tuple calls was an undocumented and unsupported feature which allowed the module argument for an apply operation to be a tuple: Var = dict:new(), Var:size(). This "feature" frequently caused confusion, especially when such call failed. The stacktrace would point out functions that don't exist in the source code.
For legacy code that need to use parameterized modules or tuple calls for some other reason, there is a new compiler option called tuple_calls. When this option is given, the compiler will generate extra code that emulates the old behavior for calls where the module is a variable.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-14497
In code such as example({ok, Val}) -> {ok, Val}. a tuple would be built. The compiler will now automatically rewrite the code to example({ok,Val}=Tuple) -> Tuple. which will reduce code size, execution time, and remove GC pressure.
Own Id: OTP-14505
The optimization of case expression where only one of the case arms can execute successfully has been improved.
Own Id: OTP-14525
Some uses of binary matching has been slightly improved, eliminating unnecessary register shuffling.
Own Id: OTP-14594 Aux Id: ERL-444
There is a new {compile_info,Info} option for the compiler that allows BEAM-based languages such as Elixir and LFE to add their own compiler versions.
Own Id: OTP-14615 Aux Id: PR-1558
Loaded BEAM code in a 64-bit system requires less memory because of better packing of operands for instructions.
These memory savings were achieved by major improvements to the beam_makeops scripts used when building the run time system and BEAM compiler. There is also new for documentation for beam_makeops that describes how new BEAM instructions and loader transformations can be implemented. The documentation is found in here in a source directory or git repository: erts/emulator/internal_doc/beam_makeops.md. An online version can be found here: https://github.com/erlang/otp/blob/master/erts/emulator/internal_doc/beam_makeops.md
Own Id: OTP-14626
Size calculations for binary constructions has been somewhat optimized, producing smaller code.
Own Id: OTP-14654
When the value returned from a 'catch' expression is ignored, no stacktrace will be built if an exception is caught. That will save time and produce less garbage. There are also some minor optimizations of 'try/catch' both in the compiler and run-time system.
Own Id: OTP-14683
There is a new syntax in 'try/catch' for retrieving the stacktrace without calling 'erlang:get_stacktrace/0'. See the reference manual for a description of the new syntax. The 'erlang:get_stacktrace/0' BIF is now deprecated.
Own Id: OTP-14692
The following is an internal change in the compiler, that is not noticeable for normal use of the compiler: The module v3_life has been removed. Its functionality has been simplified and integrated into v3_codegen.
Own Id: OTP-14712
The optimization of binary matching that delays creation of sub binaries (see the Efficiency Guide) could be thwarted by the argument order and could be necessary to change the argument order. The compiler has now become smarter and can handle any argument order.
Own Id: OTP-14774
When the compiler was faced with complex case expressions it would unnecessarily allocate stack elements and shuffle data between x and y registers. Improved code generation to only allocate a stack frame when strictly necessary.
Own Id: OTP-14808 Aux Id: ERL-514
There is a new option 'makedep_side_effect' for the compiler and -MMD for 'erlc' that generates dependencies and continues to compile as normal.
Own Id: OTP-14830
When compiling modules with huge functions, the compiler would generate a lot of atoms for its internal, sometimes so many that the atom table would overflow. The compiler has been rewritten to generate far less internal atoms to avoid filling the atom table.
Own Id: OTP-14968 Aux Id: ERL-563
External funs with literal values for module, name, and arity (e.g. erlang:abs/1) are now treated as literals. That means more efficient code that produces less garbage on the heap.
Own Id: OTP-15003
Two new guards BIFs operating on maps have been added: map_get/2 and is_map_key/2. They do the same as maps:get/2 and maps:is_key/2, respectively, except that they are allowed to be used in guards.
Own Id: OTP-15037 Aux Id: PR-1784, PR-1802
A call or apply of a literal external fun will be replaced with a direct call.
Own Id: OTP-15044 Aux Id: ERL-614
Part of EEP-44 has been implemented.
There is a new predefined macro called OTP_RELEASE which is an integer indicating the OTP release number (its value is 21 in this release).
There are new preprocessor directives -if(Condition). and -elif(Condition).. The if/elif supports the builtin function defined(Symbol).
Own Id: OTP-15087 Aux Id: PR-1810

Compiler 7.1.5.2

Fixed Bugs and Malfunctions

Fix a regression in OTP-15204 that removed .beam file metadata that some external build tools relied on.
Own Id: OTP-15292

Compiler 7.1.5.1

Fixed Bugs and Malfunctions

Fixed an issue where files compiled with the +deterministic option differed if they were compiled in a different directory but were otherwise identical.
Own Id: OTP-15204 Aux Id: ERL-679

Compiler 7.1.5

Fixed Bugs and Malfunctions

The internal compiler pass (beam_validator) that validates the generated code has been strengthened.
When compiling from BEAM assembly code, the beam_type optimizer pass could make the code unsafe. Corrected.
Own Id: OTP-14863
Corrected optimizations of integers matched out from binaries and used in bit operations.
Own Id: OTP-14898

Compiler 7.1.4

Fixed Bugs and Malfunctions

The 'deterministic' option was not recognized when given in a -compile() attribute in the source code.
Own Id: OTP-14773 Aux Id: ERL-498

Compiler 7.1.3

Fixed Bugs and Malfunctions

The compiler could issue an incorrect internal consistency failure diagnostic for some complicated bit syntax matches.
Own Id: OTP-14640 Aux Id: ERL-490

Compiler 7.1.2

Fixed Bugs and Malfunctions

Fail labels on guard BIFs weren't taken into account during an optimization pass, and a bug in the validation pass sometimes prevented this from being noticed when a fault occurred.
Own Id: OTP-14522 Aux Id: ERIERL-48
When compiling from Core Erlang, an 'apply' with a nested apply in the function position would be treated as an invalid call. Corrected. (Thanks to Mikael Pettersson for reporting this bug.)
Own Id: OTP-14526
Fixed checking of binary matching in the beam_validator module to ensure that potential compiler bugs are found at compile-time instead as emulator crash at run-time.
Own Id: OTP-14591
There could be false warnings for erlang:get_stacktrace/0 being used outside of a try block when using multiple catch clauses.
Own Id: OTP-14600 Aux Id: ERL-478

Improvements and New Features

The Erlang code linter no longer checks that the functions mentioned in nowarn_deprecated_function options are declared in the module.
Own Id: OTP-14378

Compiler 7.1.1

Fixed Bugs and Malfunctions

Fail labels on guard BIFs weren't taken into account during an optimization pass, and a bug in the validation pass sometimes prevented this from being noticed when a fault occurred.
Own Id: OTP-14522 Aux Id: ERIERL-48

Compiler 7.1

Fixed Bugs and Malfunctions

For many releases, it has been legal to override a BIF with a local function having the same name. However, calling a local function with the same name as guard BIF as filter in a list comprehension was not allowed.
Own Id: OTP-13690
compile:forms/2 would not return the module name as documented when one of the options 'from_core', 'from_asm', or 'from_beam' was given. Also, the compiler would crash if one of those options was combined with 'native'.
Own Id: OTP-14408 Aux Id: ERL-417

Improvements and New Features

Optimized test for tuples with an atom as first element.
Own Id: OTP-12148
Compilation of modules with huge literal binary strings is now much faster.
Own Id: OTP-13794
Replaced usage of deprecated symbolic time unit representations.
Own Id: OTP-13831 Aux Id: OTP-13735
The undocumented and unsupported module sys_pre_expand has been removed. As a partial replacement for the functionality, there is a new function erl_internal:add_predefined_functions/1 and erl_expand_records will now add a module prefix to calls to BIFs and imported functions.
Own Id: OTP-13856
The internal compiler passes now start all generated variables with "@" to avoid any conflicts with variables in languages such as Elixir or LFE.
Own Id: OTP-13924
The function fmod/2 has been added to the math module.
Own Id: OTP-14000
Code generation for complicated guards have been improved.
Own Id: OTP-14042
The compiler has new warnings for repeated identical map keys.
A map expression such as,
#{'a' => 1, 'b' => 2, 'a' => 3}.
will produce a warning for the repeated key 'a'.
Own Id: OTP-14058
By default, there will now be a warning when export_all is used. The warning can be disabled using nowarn_export_all.
Own Id: OTP-14071
Optimize maps pattern matching by only examining the common keys in each clause first instead of all keys. This will reduce the number of lookups of each key in maps pattern matching.
Own Id: OTP-14072
There is a new 'deterministic' option to omit 'source' and 'options' tuples in the BEAM file.
Own Id: OTP-14087
Analyzing modules with binary construction with huge strings is now much faster. The compiler also compiles such modules slightly faster.
Own Id: OTP-14125 Aux Id: ERL-308
Atoms may now contain arbitrary Unicode characters.
Own Id: OTP-14178
compile:file/2 now accepts the option extra_chunks to include extra chunks in the BEAM file.
Own Id: OTP-14221
The format of debug information that is stored in BEAM files (when debug_info is used) has been changed. The purpose of the change is to better support other BEAM-based languages such as Elixir or LFE.
All tools included in OTP (dialyzer, debugger, cover, and so on) will handle both the new format and the previous format. Tools that retrieve the debug information using beam_lib:chunk(Beam, [abstract_code]) will continue to work with both the new and old format. Tools that call beam_lib:chunk(Beam, ["Abst"]) will not work with the new format.
For more information, see the description of debug_info in the documentation for beam_lib and the description of the {debug_info,{Backend,Data}} option in the documentation for compile.
Own Id: OTP-14369 Aux Id: PR-1367
In a future release, erlang:get_stacktrace/0 will probably only work when called from within a 'try' expression (otherwise it will return [].
To help prepare for that change, the compiler will now by default warn if 'get_stacktrace/0' is used in a way that will not work in the future. Note that the warning will not be issued if 'get_stacktrace/0' is used in a function that uses neither 'catch' nor 'try' (because that could be a legal use if the function is called from within a 'try'.
Own Id: OTP-14401

Compiler 7.0.4.1

Fixed Bugs and Malfunctions

Fail labels on guard BIFs weren't taken into account during an optimization pass, and a bug in the validation pass sometimes prevented this from being noticed when a fault occurred.
Own Id: OTP-14522 Aux Id: ERIERL-48

Compiler 7.0.4

Fixed Bugs and Malfunctions

Minor internal changes. A typo in the documentation was also fixed.
Own Id: OTP-14240

Compiler 7.0.3

Fixed Bugs and Malfunctions

Fixed a compiler crash when maps were matched.
Own Id: OTP-13931 Aux Id: ERL-266
Fixed a compiler crash having to with the delayed sub-creation optimization. (Thanks to Jose Valim for reporting this bug.)
Own Id: OTP-13947 Aux Id: ERL-268
The compiler option inline_list_funcs accidentally turned off some other optimizations.
Own Id: OTP-13985
The compiler could sometimes generate spurious warnings when inlining was enabled.
Own Id: OTP-14040 Aux Id: ERL-301

Compiler 7.0.2

Fixed Bugs and Malfunctions

If the compiler fails to write the BEAM file, it will now report the reason of the error for the write operation.
Own Id: OTP-13701
Fixed an internal compiler error. (Thanks to Svilen Ivanov for reporting this bug.)
Own Id: OTP-13780 Aux Id: ERL-202
The compiler could crash when trying to compile a complicated expression with multiple catches all on one line . (Thanks to Thomas Arts for reporting this bug.)
Own Id: OTP-13804 Aux Id: ERL-209
Eliminated a few internal compiler failures.
Own Id: OTP-13863

Compiler 7.0.1

Fixed Bugs and Malfunctions

A literal binary matching regression was introduced in 19.0 where a match could fail to resolve to the right clause. This has now been fixed.
Own Id: OTP-13738

Compiler 7.0

Fixed Bugs and Malfunctions

compile:forms/1,2 would crash when used in a working directory that had been deleted by another process.
Own Id: OTP-13430 Aux Id: ERL-113
Dialyzer no longer crashes when there is an invalid function call such as 42(7) in a module being analyzed. The compiler will now warn for invalid function calls such as X = 42, x(7).
Own Id: OTP-13552 Aux Id: ERL-138

Improvements and New Features

Optimization of tuple matching has been slightly improved.
Own Id: OTP-12951
Five deprecated and undocumented functions in the module core_lib have been removed. The functions are: get_anno/{1,2}, is_literal/1, is_literal_list/1, and literal_value. Use the appropriate functions in the cerl module instead.
Own Id: OTP-12979
The pre-processor can now expand the ?FUNCTION_NAME and ?FUNCTION_ARITY macros.
Own Id: OTP-13059
The function mapfold/4 has been added to the cerl_trees module.
Own Id: OTP-13280
Bitstring comprehensions have been generalized to allow arbitrary expressions in the construction part.
Own Id: OTP-13289
The compiler will now produce warnings for binary patterns that will never match (example: <<-1/unsigned>> = Bin).
Own Id: OTP-13374 Aux Id: ERL-44
The compiler will no longer put the compilation date and time into BEAM files. That means that two BEAM files compiled on the same computer from the same source code and compilation options will be identical.
Note: If you want to find out whether a BEAM file on disk is different from the loaded code, compared the MD5 value obtained from Mod:module_info(md5) with the MD5 value obtained from beam_lib:md5(BeamFileForMod)
.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-13504
The function compile:env_compiler_options/0 has been added to allow tools to pick up the same default compiler options as the compiler itself.
Own Id: OTP-13654

Compiler 6.0.3.1

Fixed Bugs and Malfunctions

Fail labels on guard BIFs weren't taken into account during an optimization pass, and a bug in the validation pass sometimes prevented this from being noticed when a fault occurred.
Own Id: OTP-14522 Aux Id: ERIERL-48

Compiler 6.0.3

Fixed Bugs and Malfunctions

An complicated guard expression in a function call could crash the compiler. (Thanks to Thomas Arts for reporting this bug.)
Own Id: OTP-13208
Constructing a map in a guard in a catch could crash the compiler. (Thanks to Thomas Arts for reporting this bug.)
Own Id: OTP-13223
Updating a fun as if it were a map would cause the compiler to crash. (Thanks to Thomas Arts for reporting this bug.)
Own Id: OTP-13231
Fix pretty printing of Core Maps
Literal maps could cause Dialyzer to crash when pretty printing the results.
Own Id: OTP-13238
A complex combination of bit syntax matching operations would cause an internal consistency check failure during compilation. (Thanks to Jose Valim for reporting this bug.)
Own Id: OTP-13309

Compiler 6.0.2

Fixed Bugs and Malfunctions

Fix cerl_trees:label/2 bug with map K/V swap
Own Id: OTP-13091
Warnings produced when the 'bin_opt_info' option was given could sometimes lack filenames and line numbers. (Thanks to José Valim for reporting this bug.)
Own Id: OTP-13113

Compiler 6.0.1

Fixed Bugs and Malfunctions

Fix get_map_elements register corruption
Instruction get_map_elements 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.
Own Id: OTP-12967

Compiler 6.0

Fixed Bugs and Malfunctions

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.
Own Id: OTP-12453
Using a map could incorrectly suppress warnings for unused variables.
Own Id: OTP-12515
The compiler now properly reports unknown parse transforms. That is, undef exceptions coming from the parse transform itself is reported differently from the absence of the parse transform.
Own Id: OTP-12723
Allow for 'creation of sub binary delayed' optimization if maps instructions are in a clause.
Own Id: OTP-12758

Improvements and New Features

The cerl and cerl_trees modules in the Compiler application are now documented.
Own Id: OTP-11978
The deprecated 'asm' option has been removed.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-12100
Support variables as Map keys in expressions and patterns
Erlang will accept any expression as keys in Map expressions and it will accept literals or bound variables as keys in Map patterns.
Own Id: OTP-12218
Infer Map type information in beam_type compiler optimization pass.
Own Id: OTP-12253
Compiler optimizations have been improved.
Own Id: OTP-12393
Five undocumented functions in the module core_lib have been deprecated and will be removed in the next major release. The functions are: get_anno/{1,2}, is_literal/1, is_literal_list/1, and literal_value. Use the appropriate functions in the cerl module instead.
Own Id: OTP-12497
Change some internal data structures to Maps in order to speed up compilation time. Measured speed up is around 10%-15%.
Own Id: OTP-12774
Fix beam_bool pass for Maps instruction get_map_elements
Before beam_split the get_map_elements instruction is still in blocks and the helper function in beam_jump did not reflect this.
Own Id: OTP-12844 Aux Id: 17

Compiler 5.0.4

Fixed Bugs and Malfunctions

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.)
Own Id: OTP-12402
The compiler would crash when compiling some complex, nonsensical guards such as:
... when {{X}}, -X...
Own Id: OTP-12410
In rare circumstances, using binary pattern in the value part of a map pattern would cause the compiler to crash.
Own Id: OTP-12414
Case expressions where a map was wrapped in a tuple or list such as:
case {a,Map} of
{a,#{k:=_}}=Tuple -> Tuple
end.
would be unsafely "optimized" to either cause an exception at run-time or would return an empty map.
Own Id: OTP-12451
When a variable was compared to a literal map using the '==' operator, the compiler would change the operator to '=:=' 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.
Own Id: OTP-12456

Compiler 5.0.3

Fixed Bugs and Malfunctions

Named funs with the same name and arity could get mixed up with each other.
Own Id: OTP-12262
Coalesce map keys in dialyzer mode
This fixes a regression introduced in commit 805f9c89fc01220bc1bb0f27e1b68fd4eca688ba The problem occurred with compounded map keys compiled with dialyzer option turned on, '+dialyzer'.
Reported by: Ivan Uemlianin
Own Id: OTP-12347

Compiler 5.0.2

Fixed Bugs and Malfunctions

Corrected a bug with incorrect code generation when inlining was turned on.
Own Id: OTP-12132

Compiler 5.0.1

Fixed Bugs and Malfunctions

A Dialyzer crash involving analysis of Map types has now been fixed.
Own Id: OTP-11947
The compiler would fail to compile a file with a latin-1 character in the false branch of an -ifdef or -indef.
Own Id: OTP-11987

Compiler 5.0

Fixed Bugs and Malfunctions

Line numbers would not be correct when a binary construction such as '<<Bin/binary,...>>' fails. (Thanks to Stanislav Seletskiy for reporting this bug.)
Own Id: OTP-11572
The compiler now properly annotates the code in value in the 'after' clause for a 'try' so that Dialyzer no longer generates a false warning for an unmatched return.
Own Id: OTP-11580
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.)
Own Id: OTP-11610
With --Wunmatched_returns, 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 '[io:format(...) || ...]' will not cause a warning, while ignoring '[file:close(Fd) || ...]' will.
Own Id: OTP-11626
Matching out a binary and applying the binary as if it were a fun would crash the run-time system. (Thanks to Loïc Hoguin.)
Own Id: OTP-11672
Some local implementations of removing the last element from a list are replaced by lists:droplast/1. Note that this requires at least stdlib-2.0, which is the stdlib version delivered in OTP 17.0. (Thanks to Hans Svensson)
Own Id: OTP-11678
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.)
Own Id: OTP-11682
Application upgrade (appup) files are corrected for the following applications:
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
A new test utility for testing appup files is added to test_server. This is now used by most applications in OTP.
(Thanks to Tobias Schlager)
Own Id: OTP-11744
Adapt 'asm' deprecation message to new version scheme. (Thanks to Tuncer Ayaz)
Own Id: OTP-11751
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.
Own Id: OTP-11770

Improvements and New Features

Compilation times for modules with a huge number for record accesses using the dot operator has been improved.
Own Id: OTP-10652
The compiler can generate somewhat better code by moving let expressions into sequences. (Thanks to Anthony Ramine.)
Own Id: OTP-11056
Forbid unsized fields in patterns of binary generators and simplified v3_core's translation of bit string generators. (Thanks to Anthony Ramine.)
Own Id: OTP-11186
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.
Own Id: OTP-11537
Using the from_asm 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.)
Own Id: OTP-11544
The .core and .S extensions are now documented in the erlc documentation, and the 'from_core' and 'from_asm' options are now documented in the compiler documentation. (Thanks to Tuncer Ayaz.)
Own Id: OTP-11547
Optimization of case expressions that build tuples or lists have been improved.
Own Id: OTP-11584
EEP43: New data type - Maps
With Maps you may for instance:
- ____ - M0 = #{ a => 1, b => 2}, % create associations
- ____ - M1 = M0#{ a := 10 }, % update values
- ____ - M2 = M1#{ "hi" => "hello"}, % add new associations
- ____ - #{ "hi" := V1, a := V2, b := V3} = M2. % match keys with values
For information on how to use Maps please see Map Expressions in the Reference Manual.
The current implementation is without the following features:
- ____ - No variable keys
- ____ - No single value access
- ____ - No map comprehensions
Note that Maps is experimental during OTP 17.0.
Own Id: OTP-11616
Some function specs are corrected or moved and some edoc comments are corrected in order to allow use of edoc. (Thanks to Pierre Fenoll)
Own Id: OTP-11702
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.
Own Id: OTP-11720
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.
Own Id: OTP-11791

Compiler 4.9.4

Fixed Bugs and Malfunctions

Typo fix ambigous -> ambiguous. Thanks to Leo Correa.
Own Id: OTP-11455

Improvements and New Features

Lift 'after' blocks to zeroary functions. Thanks to Anthony Ramine.
Own Id: OTP-11267

Compiler 4.9.3

Fixed Bugs and Malfunctions

Expressions such as 'B = is_integer(V), if B and B -> ok end' would crash the compiler.
Own Id: OTP-11240
compile:file2/2 with the option report_errors 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 'none' if no line number is applicable.
Own Id: OTP-11304 Aux Id: seq12412

Improvements and New Features

Fix matching of floating point middle-endian machines. Thanks to Johannes Weissl.
Own Id: OTP-11201
Restrict inlining of local fun references. Thanks to Anthony Ramine.
Own Id: OTP-11211
Silence a misleading warning with some comprehensions. Thanks to Anthony Ramine.
Own Id: OTP-11212
Forbid returning a match context in beam_validator. Thanks to Anthony Ramine.
Own Id: OTP-11247

Compiler 4.9.2

Fixed Bugs and Malfunctions

Compiling functions with complex boolean operations in guards could be very slow. (Thanks to Magnus Muller for reporting this issue.)
Own Id: OTP-10939
Certain guard expressions used in a receive statement could cause the compiler to crash.
Own Id: OTP-11119 Aux Id: seq12342

Improvements and New Features

Fix optimization of some binary comprehensions. Thanks to Anthony Ramine.
Own Id: OTP-11005
Use a set to store ref registers in beam_receive. Thanks to Anthony Ramine.
Own Id: OTP-11069
Fix renaming of bs_put_string instructions. Thanks to Anthony Ramine.
Own Id: OTP-11129

Compiler 4.9.1

Fixed Bugs and Malfunctions

The compiler would crash attempting to compile expressions such as "element(2, not_tuple)".
Own Id: OTP-10794
Forbid multiple values in Core Erlang sequence arguments. Thanks to José Valim and Anthony Ramine.
Own Id: OTP-10818
An unsafe optimization would cause the compiler to crash with an internal error for certain complex code sequences.
Own Id: OTP-10825 Aux Id: seq12247

Improvements and New Features

Integers in expression that will give a floating point result (such as "X / 2" will now be converted to floating point at compile-time. (Suggested by Richard O'Keefe.)
Identical floating points constans in a module will now be coalesced to one entry in the constant pool.
Own Id: OTP-10788

Compiler 4.9

Improvements and New Features

The compiler optimizations have been polished, so that the code quality will be slightly better in some cases.
Own Id: OTP-10193
Support for Unicode has been implemented.
Own Id: OTP-10302
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.
Own Id: OTP-10630
Fix some wrong warnings triggered by the option inline_list_funcs. Thanks to Anthony Ramine.
Own Id: OTP-10690
Forbid local fun variables in Core Erlang guards. Thanks to Anthony Ramine.
Own Id: OTP-10706
Binary syntax matches could cause an internal consistency error in in the compiler. (Thanks to Viktor Sovietov for reporting this bug.)
Own Id: OTP-10724

Compiler 4.8.2

Fixed Bugs and Malfunctions

Modules with very many functions would compile very slowly.
Own Id: OTP-10123
compile:forms/2 will now use a {source,SourceFilePath} to set the source returned by module_info(compile) (Thanks to José Valim)
Own Id: OTP-10150
A process which had enabled trap_exit would receive EXIT messages after calling the compiler. (Thanks to Jeremy Heater.)
Own Id: OTP-10171
Fix messages ordering with column numbers
Own Id: OTP-10183
sys_pre_expand: Fix BASE never being set
Commit a612e99fb5aaa934fe5a8591db0f083d7fa0b20a turned module attributes from 2-tuples to 3-tuples but forgot to update get_base/1, breaking BASE for parametric modules.
Own Id: OTP-10184
The compiler will now issue a warning if literal tuple funs are used. For example, {erlang,is_tuple}(X) will now generate a warning.
Own Id: OTP-10185
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.
Own Id: OTP-10197
Fix the erlc -MP flag
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.
Own Id: OTP-10211

Compiler 4.8.1

Fixed Bugs and Malfunctions

In rare circumstance, the compiler could crash when compiling a case statement. (Thanks to Hakan Mattsson.)
Own Id: OTP-9842
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.
Own Id: OTP-9866
Using get/1 in a try block could in some cases cause an internal compiler error. (Thanks to Eric Merritt.)
Own Id: OTP-9867
An unexported on_load function would not get run if the module was compiled with the inline option. (Thanks to Yiannis Tsiouris.)
Own Id: OTP-9910
Fixed a discrepancy in compile_info
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.
Own Id: OTP-9917
Fix typo in `compile' doc: unmatched parenthesis (Thanks to Ricardo Catalinas Jiménez)
Own Id: OTP-9919
In a try...catch statement that always returned false, the compiler would remove calls to BIFs that could not cause an exception (such as put/2). Example of such code: try put(K, V), false catch _:_ -> false end.
Own Id: OTP-9982

Compiler 4.8

Fixed Bugs and Malfunctions

Add '-callback' attributes in stdlib's behaviours
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
'behaviour_info(callbacks)' is a special function that is defined in a module which describes a behaviour and returns a list of its callbacks.
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
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.
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.
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
Own Id: OTP-9621
The calculation of the 'uniq' value for a fun (see erlang:fun_info/1) 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.
Own Id: OTP-9667

Improvements and New Features

Variables are now now allowed in 'fun M:F/A' as suggested by Richard O'Keefe in EEP-23.
The representation of 'fun M:F/A' 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 syntax_tools application can also handle both formats.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-9643
filename:find_src/1,2 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 M:module_info(compile) (because those options will be applied anyway if the module is re-compiled).
Own Id: OTP-9752
Inlining binary matching could cause an internal compiler error. (Thanks to Rene Kijewski for reporting this bug.)
Own Id: OTP-9770

Compiler 4.7.5

Fixed Bugs and Malfunctions

Compiler options given in the source code using a -compile() attribute used to be included twice in Mod:module_info(compile). They are now only included once at the beginning of the list of options.
Own Id: OTP-9534
beam_disasm: Handle stripped BEAM files
beam_disasm:file/1 would crash if asked to disassemble a stripped BEAM file without an "Attr" chunk. (Thanks to Haitao Li)
Own Id: OTP-9571

Compiler 4.7.4

Fixed Bugs and Malfunctions

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.)
Own Id: OTP-9134
Eliminate incorrect warning in sys_core_fold
Own Id: OTP-9152

Compiler 4.7.3

Fixed Bugs and Malfunctions

The -export_type() directive is no longer included among the attributes.
Own Id: OTP-8998

Improvements and New Features

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.
Own Id: OTP-9049
Dependency generation for Makefiles has been added to the compiler and erlc. See the manual pages for compile and erlc. (Thanks to Jean-Sebastien Pedron.)
Own Id: OTP-9065

Compiler 4.7.2

Fixed Bugs and Malfunctions

Two compiler bugs (that would cause the compiler to terminate) reported by Christopher Williams have been fixed.
Own Id: OTP-8949

Improvements and New Features

The compiler would translate binary comprehensions containing tail segments in a way that would would confuse Dialyzer. For instance:
[42 || <<_:8/integer, _/bits>> <= Bits]
would produce a Dialyzer warning.
Own Id: OTP-8864
Code such as foo(A) -> <<A:0>> would crash the compiler.
Own Id: OTP-8865
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.)
Own Id: OTP-8888

Compiler 4.7.1

Improvements and New Features

Eliminated warnings for auto-imported BIF clashes.
Own Id: OTP-8840

Compiler 4.7

Fixed Bugs and Malfunctions

Several problems in the inliner have been fixed.
Own Id: OTP-8552

Improvements and New Features

The module binary from EEP31 (and EEP9) is implemented.
Own Id: OTP-8217
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:
- 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
- Explicitly importing a function having a name clashing with the name of an autoimported BIF that was present (and autoimported) before OTP R14A
- Using any form of the old compiler directive nowarn_bif_clash
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,
To resolve clashes, you can either use the explicit module name erlang to call the BIF, or you can remove the auto-import of that specific BIF by using the new compiler directive -compile({no_auto_import,[F/A]})., which makes all calls to the local or imported function without explicit module name pass without warnings or errors.
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 nowarn_bif_clash compiler directive, might need changing to be accepted by the compiler.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-8579
The undocumented, unsupported, and deprecated function lists:flat_length/1 has been removed.
Own Id: OTP-8584
Nested records can now be accessed without parenthesis. See the Reference Manual for examples. (Thanks to YAMASHINA Hio and Tuncer Ayaz.)
Own Id: OTP-8597
It is now possible to suppress the warning in code such as "list_to_integer(S), ok" by assigning the ignored value "" like this: "` = list_to_integer(S), ok`".
Own Id: OTP-8602
receive 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 gen_server:call(). (See gen:do_call/4 for an example of a receive statement that will be optimized.)
Own Id: OTP-8623
The compiler optimizes record operations better.
Own Id: OTP-8668

Compiler 4.6.5

Fixed Bugs and Malfunctions

Using complex boolean expressions in ifs could cause the compiler to either crash or terminate with an internal error. (Thanks to Simon Cornish.)
Own Id: OTP-8338
Bit string comprehensions can now be used in parameterized modules. (Thanks to Jebu Ittiachen.)
Own Id: OTP-8447

Improvements and New Features

The expected return value for an on_load function has been changed. (See the section about code loading in the Reference manual.)
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-8339
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.)
Own Id: OTP-8378
The -Werror option for erlc and the compiler option warnings_as_errors will cause warnings to be treated as errors. (Thanks to Christopher Faulet.)
Own Id: OTP-8382
Macros overloading has been implemented. (Thanks to Christopher Faulet.)
Own Id: OTP-8388

Compiler 4.6.4

Fixed Bugs and Malfunctions

The compiler's 'E' option now works with modules with types and specifications.
Own Id: OTP-8238 Aux Id: OTP-8150
Certain uses of binary matching in a begin-end in a list comprehension could cause the compiler to crash or generate incorrect code.
Own Id: OTP-8271

Improvements and New Features

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.
Own Id: OTP-8201
The compiler could crash if invalid calls to is_record/2 was used in (for example) a list comprehension. (Thanks to Tobias Lindahl.)
Own Id: OTP-8269
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.
Own Id: OTP-8295

Compiler 4.6.3

Improvements and New Features

Corrected liveness optimization to eliminate a compiler crash that could occur when compiling bit syntax construction code. (Thanks to Mikage Sawatari.)
Calling BIFs such as length/1 in guard context in a try/catch block could cause a compiler crash. (Thanks to Paul Fisher.)
Using filter expressions containing andalso or orelse in a list comprehension could cause a compiler crash. (Thanks to Martin Engström.)
Own Id: OTP-8054
A guard with nested 'not' operators could cause the compiler to crash. (Thanks to Tuncer Ayaz.)
Own Id: OTP-8131

Compiler 4.6.2

Fixed Bugs and Malfunctions

The compiler would crash while compiling certain complex function bodies containing receive after 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.)
Own Id: OTP-7980

Compiler 4.6.1

Fixed Bugs and Malfunctions

Miscellaneous minor bugs fixed.
Own Id: OTP-7937

Improvements and New Features

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.
Own Id: OTP-7924
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.
Own Id: OTP-7927

Compiler 4.6.0.1

Fixed Bugs and Malfunctions

Using andalso/orelse or record access in a try...catch could cause a compiler crash.
Some large and complex functions could require extremely long compilation times (hours or days).
Own Id: OTP-7905

Compiler 4.6

Fixed Bugs and Malfunctions

For some complex guards which used andalso/orelse, the compiler would crash. (Thanks to Hunter Morris.)
Own Id: OTP-7679
Code that (incorrectly) used the the value of nested applications of setelement/3 in bit syntax construction could crash the compiler.
Own Id: OTP-7690
Modules containing huge integers (consisting of several hundreds of thousands of digits or more) could be slow to compile. This problem has been corrected.
Own Id: OTP-7707 Aux Id: seq11129
If the generator in a list comprehension is given a non-list term, there will now be function_clause exception instead of a case_clause exception (as it was in all releases before R12B).
Own Id: OTP-7844

Improvements and New Features

The compiler could crash if the size for a binary segment in matching was a complex literal such as binary or tuple.
Own Id: OTP-7650
The compiler generates more compact and faster code for matching of complex constants (such as constant lists and tuples).
Own Id: OTP-7655
The undocumented, unsupported, and deprecated guard BIF is_constant/1 has been removed.
* INCOMPATIBILITY with R12B *
Own Id: OTP-7673
The compiler generates better code for many guard expressions, and especially for guards that use andalso/orelse or record fields.
(In technical terms, andalso/orelse 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.)
Own Id: OTP-7718
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.
Own Id: OTP-7737
The short-circuit operators andalso and orelse no longer guarantees that their second argument is either true or false. As a consequence, andalso/orelse are now tail-recursive.
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-7748
The compiler will refuse to a compile file where the module name in the file differs from the output file name.
When compiling using erlc, the current working directory will no be included in the code path (unless explicitly added using "-pa .").
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-7793
There will no longer be any warnings for list comprehensions without generators, as such list comprehension have turned out to be useful.
Own Id: OTP-7846
Warnings for obsolete guard tests are now turned on. (That is, writing list(L) in a guard instead of is_list(L) will generate a warning.)
The warnings can be turned off using the nowarn_obsolete_guard option.
Own Id: OTP-7850
The copyright notices have been updated.
Own Id: OTP-7851
If a module contains an exported function with the same name as an auto-imported BIF (such as length/1), any calls to the BIF must have an explicit erlang: prefix, or there will be a compilation error (such calls would only generate a warning in previous releases).
(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.)
* POTENTIAL INCOMPATIBILITY *
Own Id: OTP-7873

Compiler 4.5.5

Fixed Bugs and Malfunctions

Matching on a zero-width segment in the bit syntax would crash the compiler. (Thanks to Will.)
Own Id: OTP-7591

Improvements and New Features

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.
Own Id: OTP-7556
In user-defined attributes, Name/Arity is now allowed and will be translated to {Name,Arity}. (An implementation of EEP-24 by Richard O'Keefe.)
The module_info/{0,1} functions automatically inserted into each compiled modules are now documented in the Modules section in the Reference Manual.
Own Id: OTP-7586

Compiler 4.5.4

Improvements and New Features

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.)
Own Id: OTP-7498

Compiler 4.5.3

Improvements and New Features

New option warn_export_all to warn for a module using export_all. (Thanks to Richard Carlsson.)
Own Id: OTP-7392

Compiler 4.5.2.1

Fixed Bugs and Malfunctions

In rare circumstances, the length/1 BIF (and a few other guard BIFs) would seem to return an incorrect value (of any type).
Own Id: OTP-7345 Aux Id: seq10962

Compiler 4.5.2

Fixed Bugs and Malfunctions

A bug in the old inliner has been fixed. Some undocumented functionality has been removed.
Own Id: OTP-7223
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 '='.
Own Id: OTP-7227
Complex combinations of record operations and binary matching could cause the compiler to crash. (Thanks to Vladimir Klebansky.)
Own Id: OTP-7233
In rare circumstances, mixing binary matching clauses with clauses matching other data types, the compiler could crash.
Own Id: OTP-7240 Aux Id: seq10916

Compiler 4.5.1.1

Fixed Bugs and Malfunctions

Corrected a compiler bug that could cause a complex binary matching operation to fail when it shouldn't. (Thanks to Tomas Stejskal.)
Own Id: OTP-7188
In unusual circumstances, the environment for a fun could bind wrong values.
Own Id: OTP-7202 Aux Id: seq10887
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 '[...||...]++Expr', Expr is now evaluated before the list comprehension. This change is backwards compatible (see the following note about evaluation order if you have doubts).
Note about evaluation order: The Reference manual says that subexpressions are evaluated in any order before the expression itself. Therefore, in an expression such as 'LeftExpr++RightExpr', you should not depend on LeftExpr being evaluated before RightExpr 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 ETS operations.
Own Id: OTP-7206

Compiler 4.5.1

Fixed Bugs and Malfunctions

A match expression inside a function call could cause a false "a term is constructed but never used" warning.
Own Id: OTP-7018 Aux Id: seq10824
The compiler could crash if a binary tail was matched out, and then used in a binary append operation. (Thanks to Oleg Avdeev.)
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.)
Own Id: OTP-7022
Matching an empty binary in a record and then using the same record again could cause a compiler crash. (Thanks to Fredrik Thulin.)
Own Id: OTP-7029
In rare circumstances, constants containing floating points and integers could be confused. Example:
f(a) -> [1]; f(b) -> [1.0].
Both f(a) and f(b) would return [1].
Own Id: OTP-7073
Some bit syntax code such as
matching d(_,<$lt;$gt;$gt;) -> one; d(0,<$lt;D$gt;$gt;) ->two.
could crash the compiler. (Thanks to Simon Cornish.)
Own Id: OTP-7094
In unusual circumstances, a call to a fun could fail due to an unsafe optimization. (Thanks to Simon Cornish.)
Own Id: OTP-7102
Bit syntax matching with a guard containing two or more uses of andalso/orelse could cause the compiler to crash. (Thanks to Mateusz Berezecki.)
Own Id: OTP-7113
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 erlang:'$lt;'(erlang:length(L), 2) as case expression into a guard, which would change the semantics. (Thanks to Robert Virding.)
Own Id: OTP-7117

Improvements and New Features

The compiler could generate suboptimal code for record updates if the record update code consisted of multiple source code lines.
Own Id: OTP-7101

Compiler 4.5

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

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

Compiler 4.4.5

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

Improvements and New Features

Minor Makefile changes.
Own Id: OTP-6689

Compiler 4.4.4

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

Compiler 4.4.3

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

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

Compiler 4.4.2.1

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

Compiler 4.4.2

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

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

Compiler 4.4.1

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

Compiler 4.4

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

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 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

Compiler 4.3.12

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

Compiler 4.3.11

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

Compiler 4.3.10

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

Compiler 4.3.9

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.)
Unnecessary 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

Compiler 4.3.8

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

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

Compiler 4.3.7

Improvements and New Features

Further improvements of encrypted debug info: New option encrypt_debug_info for compiler.
Own Id: OTP-5541 Aux Id: seq9837

Compiler 4.3.6

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

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

Compiler 4.3.5

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

Compiler 4.3.4

Fixed Bugs and Malfunctions

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.)
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

Compiler 4.3.3

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 matching 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

Compiler 4.3.2

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

Compiler 4.3.1

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

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