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compile(3)		   Erlang Module Definition		    compile(3)

NAME
       compile - Erlang	Compiler

DESCRIPTION
       This  module  provides an interface to the standard Erlang compiler. It
       can generate either a new file, which contains the object code, or  re-
       turn a binary, which can	be loaded directly.

EXPORTS
       env_compiler_options()

	      Return  compiler	options	 given	via  the  environment variable
	      ERL_COMPILER_OPTIONS. If the value is a list, it is returned  as
	      is. If it	is not a list, it is put into a	list.

       file(File)

	      Is  the  same  as	file(File, [verbose,report_errors,report_warn-
	      ings]).

       file(File, Options) -> CompRet

	      Types:

		 CompRet = ModRet | BinRet | ErrRet
		 ModRet	= {ok,ModuleName} | {ok,ModuleName,Warnings}
		 BinRet	= {ok,ModuleName,Binary} | {ok,ModuleName,Binary,Warn-
		 ings}
		 ErrRet	= error	| {error,Errors,Warnings}

	      Compiles	the  code  in the file File, which is an Erlang	source
	      code file	without	the .erl extension. Options determine the  be-
	      havior of	the compiler.

	      Returns {ok,ModuleName} if successful, or	error if there are er-
	      rors. An object code file	is created if the compilation succeeds
	      without  errors.	It  is considered to be	an error if the	module
	      name in the source code is not the same as the basename  of  the
	      output file.

	      Available	options:

		basic_validation:
		  This option is a fast	way to test whether a module will com-
		  pile successfully. This is useful for	code  generators  that
		  want	to  verify  the	code that they emit. No	code is	gener-
		  ated.	If warnings are	enabled,  warnings  generated  by  the
		  erl_lint  module  (such as warnings for unused variables and
		  functions) are also returned.

		  Use option strong_validation to generate all	warnings  that
		  the compiler would generate.

		strong_validation:
		  Similar  to  option  basic_validation. No code is generated,
		  but more compiler passes are run  to	ensure	that  warnings
		  generated  by	the optimization passes	are generated (such as
		  clauses that will not	match, or expressions that are guaran-
		  teed to fail with an exception at runtime).

		binary:
		  The  compiler	returns	the object code	in a binary instead of
		  creating an object file. If successful, the compiler returns
		  {ok,ModuleName,Binary}.

		bin_opt_info:
		  The  compiler	 will emit informational warnings about	binary
		  matching optimizations (both successful  and	unsuccessful).
		  For  more information, see the section about bin_opt_info in
		  the Efficiency Guide.

		{compile_info, [{atom(), term()}]}:
		  Allows compilers built on top	of  compile  to	 attach	 extra
		  compilation metadata to the compile_info chunk in the	gener-
		  ated beam file.

		  It is	advised	for compilers to remove	all  non-deterministic
		  information  if the deterministic option is supported	and it
		  was supplied by the user.

		compressed:
		  The compiler will compress the generated object code,	 which
		  can be useful	for embedded systems.

		debug_info:

		  Includes  debug  information in the form of  Erlang Abstract
		  Format in the	debug_info chunk of the	compiled beam  module.
		  Tools	 such  as  Debugger, Xref, and Cover require the debug
		  information to be included.

		  Warning: Source code can be reconstructed from the debug in-
		  formation.  Use  encrypted  debug  information  (encrypt_de-
		  bug_info) to prevent this.

		  For details, see beam_lib(3).

		{debug_info, {Backend, Data}}:

		  Includes custom debug	information in the form	of  a  Backend
		  module  with	custom	Data  in the compiled beam module. The
		  given	module must implement a	debug_info/4 function  and  is
		  responsible  for  generating different code representations,
		  as described in the debug_info under beam_lib(3).

		  Warning: Source code can be reconstructed from the debug in-
		  formation.  Use  encrypted  debug  information  (encrypt_de-
		  bug_info) to prevent this.

		{debug_info_key,KeyString}:

		{debug_info_key,{Mode,KeyString}}:

		  Includes debug information, but encrypts it so that it  can-
		  not  be  accessed without supplying the key. (To give	option
		  debug_info as	well is	allowed,  but  not  necessary.)	 Using
		  this	option is a good way to	always have the	debug informa-
		  tion available during	testing,  yet  protecting  the	source
		  code.

		  Mode is the type of crypto algorithm to be used for encrypt-
		  ing the debug	information. The default  (and	currently  the
		  only)	type is	des3_cbc.

		  For details, see beam_lib(3).

		encrypt_debug_info:

		  Similar  to  the  debug_info_key option, but the key is read
		  from an .erlang.crypt	file.

		  For details, see beam_lib(3).

		deterministic:
		  Omit the options and source tuples in	the list  returned  by
		  Module:module_info(compile),	and  reduce the	paths in stack
		  traces to the	module name alone. This	option	will  make  it
		  easier to achieve reproducible builds.

		makedep:
		  Produces  a  Makefile	rule to	track headers dependencies. No
		  object file is produced.

		  By default, this rule	is written to  _File_.Pbeam.  However,
		  if  option binary is set, nothing is written and the rule is
		  returned in Binary.

		  For example, if you have the following module:

		-module(module).

		-include_lib("eunit/include/eunit.hrl").
		-include("header.hrl").

		  The Makefile rule generated by this option looks as follows:

		module.beam: module.erl	\
		  /usr/local/lib/erlang/lib/eunit/include/eunit.hrl \
		  header.hrl

		makedep_side_effect:
		  The dependecies are created as a side	effect to  the	normal
		  compilation  process.	 This  means that the object file will
		  also be produced. This option	override the makedep option.

		{makedep_output, Output}:
		  Writes generated rules to  Output  instead  of  the  default
		  _File_.Pbeam.	Output can be a	filename or an io_device(). To
		  write	to stdout, use standard_io. However, if	binary is set,
		  nothing  is  written to Output and the result	is returned to
		  the caller with {ok, ModuleName, Binary}.

		{makedep_target, Target}:
		  Changes the name of the rule emitted to Target.

		makedep_quote_target:
		  Characters in	Target special to make(1) are quoted.

		makedep_add_missing:
		  Considers missing headers as generated files and  adds  them
		  to the dependencies.

		makedep_phony:
		  Adds a phony target for each dependency.

		'P':
		  Produces  a  listing of the parsed code, after preprocessing
		  and parse transforms,	in the file _File_.P. No  object  file
		  is produced.

		'E':
		  Produces a listing of	the code, after	all source code	trans-
		  formations have been performed, in the file _File_.E.	No ob-
		  ject file is produced.

		'S':
		  Produces  a  listing	of  the	 assembler  code  in  the file
		  _File_.S. No object file is produced.

		report_errors/report_warnings:
		  Causes errors/warnings to be printed as they occur.

		report:
		  A short form for both	report_errors and report_warnings.

		return_errors:
		  If this flag is set,	{error,ErrorList,WarningList}  is  re-
		  turned when there are	errors.

		return_warnings:
		  If this flag is set, an extra	field, containing WarningList,
		  is added to the tuples returned on success.

		warnings_as_errors:
		  Causes warnings to be	treated	as errors. This	option is sup-
		  ported since R13B04.

		return:
		  A short form for both	return_errors and return_warnings.

		verbose:
		  Causes  more verbose information from	the compiler, describ-
		  ing what it is doing.

		{source,FileName}:
		  Overrides  the  source  file	name  as  presented  in	  mod-
		  ule_info(compile) and	stack traces.

		{outdir,Dir}:
		  Sets a new directory for the object code. The	current	direc-
		  tory is used for output, except when a  directory  has  been
		  specified with this option.

		export_all:
		  Causes all functions in the module to	be exported.

		{i,Dir}:
		  Adds	Dir to the list	of directories to be searched when in-
		  cluding a  file.  When  encountering	an  -include  or  -in-
		  clude_lib  directive,	the compiler searches for header files
		  in the following directories:

		  * ".", the current working directory of the file server

		  * The	base name of the compiled file

		  * The	directories specified using option  i;	the  directory
		    specified last is searched first

		{d,Macro}:

		{d,Macro,Value}:
		  Defines  a  macro Macro to have the value Value. Macro is of
		  type atom, and Value can be any term.	The default  Value  is
		  true.

		{parse_transform,Module}:
		  Causes the parse transformation function Module:parse_trans-
		  form/2 to be applied to the parsed code before the  code  is
		  checked for errors.

		from_asm:
		  The  input  file  is	expected to be assembler code (default
		  file suffix ".S"). Notice that the format of assembler files
		  is not documented, and can change between releases.

		from_core:
		  The  input  file  is	expected to be core code (default file
		  suffix ".core"). Notice that the format of core files	is not
		  documented, and can change between releases.

		no_strict_record_tests:
		  This option is not recommended.

		  By	default,    the	   generated	code   for   operation
		  Record#record_tag.field verifies that	the tuple  Record  has
		  the  correct size for	the record, and	that the first element
		  is the tag record_tag. Use this option to omit the verifica-
		  tion code.

		no_error_module_mismatch:
		  Normally the compiler	verifies that the module name given in
		  the source code is the same as the base name of  the	output
		  file	and  refuses  to generate an output file if there is a
		  mismatch. If you have	a good reason (or  other  reason)  for
		  having  a  module  name  unrelated to	the name of the	output
		  file,	this option disables that verification (there will not
		  even be a warning if there is	a mismatch).

		{no_auto_import,[{F,A},	...]}:
		  Makes	 the  function	F/A no longer being auto-imported from
		  the erlang module, which resolves BIF	name clashes. This op-
		  tion must be used to resolve name clashes with BIFs auto-im-
		  ported before	R14A, if it is needed to call the local	 func-
		  tion with the	same name as an	auto-imported BIF without mod-
		  ule prefix.

	    Note:
		As from	R14A and forward, the compiler resolves	calls  without
		module	prefix	to  local  or imported functions before	trying
		with auto-imported BIFs. If the	BIF is to be called,  use  the
		erlang	module prefix in the call, not {no_auto_import,[{F,A},
		...]}.

		  If this option is written in the source code,	as a  -compile
		  directive,  the syntax F/A can be used instead of {F,A}, for
		  example:

		-compile({no_auto_import,[error/1]}).

		no_auto_import:
		  Do not auto-import any functions from	erlang module.

		no_line_info:
		  Omits	line number information	to produce a slightly  smaller
		  output file.

		{extra_chunks, [{binary(), binary()}]}:
		  Pass	extra chunks to	be stored in the .beam file. The extra
		  chunks must be a list	of tuples with a four byte  binary  as
		  chunk	name followed by a binary with the chunk contents. See
		  beam_lib for more information.

	      If warnings are turned on	(option	report_warnings	described ear-
	      lier),  the following options control what type of warnings that
	      are generated. Except from {warn_format,Verbosity}, the  follow-
	      ing options have two forms:

		* A warn_xxx form, to turn on the warning.

		* A nowarn_xxx form, to	turn off the warning.

	      In the descriptions that follow, the form	that is	used to	change
	      the default value	are listed.

		{warn_format, Verbosity}:
		  Causes warnings to be	emitted	for malformed  format  strings
		  as arguments to io:format and	similar	functions.

		  Verbosity selects the	number of warnings:

		  * 0 =	No warnings

		  * 1 =	Warnings for invalid format strings and	incorrect num-
		    ber	of arguments

		  * 2 =	Warnings also when the validity	cannot be checked, for
		    example, when the format string argument is	a variable.

		  The default verbosity	is 1. Verbosity	0 can also be selected
		  by option nowarn_format.

		nowarn_bif_clash:
		  This option is removed, it generates a fatal error if	used.

	    Warning:
		As from	beginning with R14A, the compiler no longer calls  the
		auto-imported  BIF if the name clashes with a local or explic-
		itly imported function,	and a  call  without  explicit	module
		name  is  issued.  Instead,  the local or imported function is
		called.	Still accepting	nowarn_bif_clash would make  a	module
		calling	 functions  clashing  with  auto-imported BIFs compile
		with both the old and new compilers, but with completely  dif-
		ferent semantics. This is why the option is removed.

		The  use  of  this option has always been discouraged. As from
		R14A, it is an error to	use it.

		To resolve BIF clashes,	 use  explicit	module	names  or  the
		{no_auto_import,[F/A]} compiler	directive.

		{nowarn_bif_clash, FAs}:
		  This option is removed, it generates a fatal error if	used.

	    Warning:
		The  use  of  this option has always been discouraged. As from
		R14A, it is an error to	use it.

		To resolve BIF clashes,	 use  explicit	module	names  or  the
		{no_auto_import,[F/A]} compiler	directive.

		nowarn_export_all:
		  Turns	 off  warnings	for uses of the	export_all option. De-
		  fault	is to emit a warning  if  option  export_all  is  also
		  given.

		warn_export_vars:
		  Emits	 warnings  for	all  implicitly	exported variables re-
		  ferred to after the primitives where	they  were  first  de-
		  fined.  By default, the compiler only	emits warnings for ex-
		  ported variables referred to in a pattern.

		nowarn_shadow_vars:
		  Turns	off warnings for "fresh" variables in  functional  ob-
		  jects	 or list comprehensions	with the same name as some al-
		  ready	defined	variable. Default is to	emit warnings for such
		  variables.

		nowarn_unused_function:
		  Turns	off warnings for unused	local functions. Default is to
		  emit warnings	for all	local functions	that  are  not	called
		  directly or indirectly by an exported	function. The compiler
		  does not include unused local	 functions  in	the  generated
		  beam	file,  but  the	 warning  is  still useful to keep the
		  source code cleaner.

		{nowarn_unused_function, FAs}:
		  Turns	 off  warnings	for  unused   local   functions	  like
		  nowarn_unused_function  does,	but only for the mentioned lo-
		  cal functions. FAs is	a tuple	{Name,Arity} or	a list of such
		  tuples.

		nowarn_deprecated_function:
		  Turns	 off  warnings	for calls to deprecated	functions. De-
		  fault	is to emit warnings for	every call to a	function known
		  by  the  compiler to be deprecated. Notice that the compiler
		  does not know	about attribute	-deprecated(), but uses	an as-
		  sembled  list	of deprecated functions	in Erlang/OTP. To do a
		  more general check, the Xref tool  can  be  used.  See  also
		  xref(3)  and	the function xref:m/1, also accessible through
		  the function c:xm/1.

		{nowarn_deprecated_function, MFAs}:
		  Turns	off warnings for calls to  deprecated  functions  like
		  nowarn_deprecated_function  does, but	only for the mentioned
		  functions. MFAs is a tuple {Module,Name,Arity} or a list  of
		  such tuples.

		nowarn_deprecated_type:
		  Turns	 off  warnings for use of deprecated types. Default is
		  to emit warnings for every use of a type known by  the  com-
		  piler	to be deprecated.

		nowarn_obsolete_guard:
		  Turns	 off warnings for calls	to old type testing BIFs, such
		  as pid/1 and list/1. See the Erlang Reference	Manual	for  a
		  complete  list  of  type  testing BIFs and their old equiva-
		  lents. Default is to emit warnings for  calls	 to  old  type
		  testing BIFs.

		warn_unused_import:
		  Emits	 warnings for unused imported functions. Default is to
		  emit no warnings for unused imported functions.

		nowarn_unused_vars:
		  By default, warnings are emitted for unused  variables,  ex-
		  cept	for  variables	beginning  with	an underscore ("Prolog
		  style	warnings"). Use	this option to turn off	this  kind  of
		  warnings.

		nowarn_unused_record:
		  Turns	 off  warnings	for unused record types. Default is to
		  emit warnings	for unused locally defined record types.

	      Another class of warnings	is generated by	 the  compiler	during
	      optimization  and	code generation. They warn about patterns that
	      will never match (such as	a=b), guards that always  evaluate  to
	      false, and expressions that always fail (such as atom+42).

	      Those warnings cannot be disabled	(except	by disabling all warn-
	      ings).

	  Note:
	      The compiler does	not warn for expressions that it does not  at-
	      tempt  to	 optimize. For example,	the compiler tries to evaluate
	      1/0, detects that	it will	cause an exception, and	emits a	 warn-
	      ing.  However,  the compiler is silent about the similar expres-
	      sion, X/0, because of the	variable in  it.  Thus,	 the  compiler
	      does  not	 even  try to evaluate and therefore it	emits no warn-
	      ings.

	  Warning:
	      The absence of warnings does not mean that there are no  remain-
	      ing errors in the	code.

	  Note:
	      All  options,  except  the  include  path	({i,Dir}), can also be
	      given in the file	with attribute -compile([Option,...]).	Attri-
	      bute -compile() is allowed after the function definitions.

	  Note:
	      The  options  {nowarn_unused_function,  FAs}, {nowarn_bif_clash,
	      FAs}, and	{nowarn_deprecated_function, MFAs} are only recognized
	      when  given  in files. They are not affected by options warn_un-
	      used_function, warn_bif_clash, or	warn_deprecated_function.

	      For debugging of the compiler, or	for pure curiosity, the	inter-
	      mediate  code  generated by each compiler	pass can be inspected.
	      To print a complete list of the options to produce  list	files,
	      type  compile:options()  at the Erlang shell prompt. The options
	      are printed in the order that the	passes are executed.  If  more
	      than one listing option is used, the one representing the	earli-
	      est pass takes effect.

	      Unrecognized options are ignored.

	      Both WarningList and ErrorList have the following	format:

	      [{FileName,[ErrorInfo]}].

	      ErrorInfo	is described later in this section.  The  filename  is
	      included	here,  as  the	compiler uses the Erlang pre-processor
	      epp, which allows	the code to be included	in other files.	It  is
	      therefore	 important to know to which file the line number of an
	      error or a warning refers.

       forms(Forms)

	      Is the same as forms(Forms,  [verbose,report_errors,report_warn-
	      ings]).

       forms(Forms, Options) ->	CompRet

	      Types:

		 Forms = [Form]
		 CompRet = BinRet | ErrRet
		 BinRet	 = {ok,ModuleName,BinaryOrCode}	| {ok,ModuleName,Bina-
		 ryOrCode,Warnings}
		 BinaryOrCode =	binary() | term()
		 ErrRet	= error	| {error,Errors,Warnings}

	      Analogous	to file/1, but takes a list of forms  (in  the	Erlang
	      abstract format representation) as first argument. Option	binary
	      is implicit, that	is, no object code file	is produced.  For  op-
	      tions that normally produce a listing file, such as 'E', the in-
	      ternal format for	that compiler pass (an	Erlang	term,  usually
	      not a binary) is returned	instead	of a binary.

       format_error(ErrorDescriptor) ->	chars()

	      Types:

		 ErrorDescriptor = errordesc()

	      Uses  an	ErrorDescriptor	 and returns a deep list of characters
	      that describes the error.	This function is  usually  called  im-
	      plicitly when an ErrorInfo structure (described in section Error
	      Information) is processed.

       output_generated(Options) -> true | false

	      Types:

		 Options = [term()]

	      Determines whether the compiler generates	a beam file  with  the
	      given  options.  true means that a beam file is generated. false
	      means that the compiler generates	some listing file,  returns  a
	      binary, or merely	checks the syntax of the source	code.

       noenv_file(File,	Options) -> CompRet

	      Works like file/2, except	that the environment variable ERL_COM-
	      PILER_OPTIONS is not consulted.

       noenv_forms(Forms, Options) -> CompRet

	      Works  like  forms/2,  except  that  the	environment   variable
	      ERL_COMPILER_OPTIONS is not consulted.

       noenv_output_generated(Options) -> true | false

	      Types:

		 Options = [term()]

	      Works like output_generated/1, except that the environment vari-
	      able ERL_COMPILER_OPTIONS	is not consulted.

DEFAULT	COMPILER OPTIONS
       The (host operating system) environment	variable  ERL_COMPILER_OPTIONS
       can be used to give default compiler options. Its value must be a valid
       Erlang term. If the value is a list, it is used as is. If it is	not  a
       list, it	is put into a list.

       The  list is appended to	any options given to file/2, forms/2, and out-
       put_generated/2.	  Use	the   alternative   functions	 noenv_file/2,
       noenv_forms/2, or noenv_output_generated/2 if you do not	want the envi-
       ronment variable	to be consulted, for example, if you are  calling  the
       compiler	recursively from inside	a parse	transform.

       The list	can be retrieved with env_compiler_options/0.

INLINING
       The compiler can	do function inlining within an Erlang module. Inlining
       means that a call to a function is replaced with	the function body with
       the  arguments  replaced	with the actual	values.	The semantics are pre-
       served, except if exceptions are	generated in the inlined code.	Excep-
       tions  are  reported  as	occurring in the function the body was inlined
       into.  Also,  function_clause  exceptions  are  converted  to   similar
       case_clause exceptions.

       When  a function	is inlined, the	original function is kept if it	is ex-
       ported (either by an explicit export or if the  option  export_all  was
       given) or if not	all calls to the function are inlined.

       Inlining	does not necessarily improve running time. For example,	inlin-
       ing can increase	Beam stack use,	which probably is detrimental to  per-
       formance	for recursive functions.

       Inlining	 is  never  default. It	must be	explicitly enabled with	a com-
       piler option or a -compile() attribute in the source module.

       To enable inlining, either use the option inline	to  let	 the  compiler
       decide  which  functions	 to  inline, or	{inline,[{Name,Arity},...]} to
       have the	compiler inline	all calls to the given functions. If  the  op-
       tion is given inside a compile directive	in an Erlang module, {Name,Ar-
       ity} can	be written as Name/Arity.

       Example of explicit inlining:

       -compile({inline,[pi/0]}).

       pi() -> 3.1416.

       Example of implicit inlining:

       -compile(inline).

       The option {inline_size,Size} controls how large	functions that are al-
       lowed to	be inlined. Default is 24, which keeps the size	of the inlined
       code roughly the	same as	the un-inlined version (only relatively	 small
       functions are inlined).

       Example:

       %% Aggressive inlining -	will increase code size.
       -compile(inline).
       -compile({inline_size,100}).

INLINING OF LIST FUNCTIONS
       The  compiler  can also inline various list manipulation	functions from
       the module list in STDLIB.

       This feature must be explicitly enabled with a  compiler	 option	 or  a
       -compile() attribute in the source module.

       To enable inlining of list functions, use option	inline_list_funcs.

       The following functions are inlined:

	 * lists:all/2

	 * lists:any/2

	 * lists:foreach/2

	 * lists:map/2

	 * lists:flatmap/2

	 * lists:filter/2

	 * lists:foldl/3

	 * lists:foldr/3

	 * lists:mapfoldl/3

	 * lists:mapfoldr/3

PARSE TRANSFORMATIONS
       Parse  transformations  are  used when a	programmer wants to use	Erlang
       syntax but with different semantics. The	original Erlang	code  is  then
       transformed into	other Erlang code.

ERROR INFORMATION
       The  ErrorInfo  mentioned  earlier is the standard ErrorInfo structure,
       which is	returned from all I/O modules. It has the following format:

       {ErrorLine, Module, ErrorDescriptor}

       ErrorLine is the	atom none if the error does not	correspond to  a  spe-
       cific line, for example,	if the source file does	not exist.

       A string	describing the error is	obtained with the following call:

       Module:format_error(ErrorDescriptor)

SEE ALSO
       epp(3), erl_id_trans(3),	erl_lint(3), beam_lib(3)

Ericsson AB			compiler 7.3.2			    compile(3)

NAME | DESCRIPTION | EXPORTS | DEFAULT COMPILER OPTIONS | INLINING | INLINING OF LIST FUNCTIONS | PARSE TRANSFORMATIONS | ERROR INFORMATION | SEE ALSO

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