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Compiler Release Notes

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This document describes the changes made to the Compiler application.

## 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() and nonempty_bitstring().

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 7.6.9.1

### 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 varible 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 maches.

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, unsupport, 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 teminate 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.

Som 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(3) for more information.

The Erlang shell always applies strict record tests.

Own Id: OTP-5915 Aux Id: OTP-5714

The BIF is_record/3 can now be used in guards. Also, is_record/3 can now be called without an erlang: module prefix for consistency with the other is_* functions.

Own Id: OTP-5916

The compiler options ignore_try and ignore_cond, which allowed code that used unquoted try or cond as atoms or record tags, has been removed. Old code that depended on the options need to be revised to have occurrences of try or cond as atom or record tags single-quoted. (Note: Although cond is a reserved keyword, there is no cond statement. It might be introduced in a future release.)

*** POTENTIAL INCOMPATIBILITY ***

Own Id: OTP-6058

## 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.)

Unecessary tests (such as a 'case' with two case branches that were identical) could cause the compiler to crash. (Thanks to Fredrik Thulin.)

The validation pass of the compiler could generate an error for correct code when floating point operations were used in try/catch statements.

In bit syntax construction, any field following a binary field would always be marked as "aligned" (which may or may not be correct). That would cause the hipe native compiler to generate incorrect code if the field was in fact unaligned. (Thanks to Per Gustafsson.)

Some complex guard expressions (such as A#a.b==""; A#a.b==undefined) would crash the compiler. (Thanks to Sean Hinde.)

Compilation speed has been increased for modules with many functions and/or atoms (such as modules generated by the Asn1 application or other code generators).

Own Id: OTP-5632 Aux Id: seq10057

## 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