Provided by: erlang-manpages_22.0.7+dfsg-1_all bug

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  return  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_warnings]).

       file(File, Options) -> CompRet

              Types:

                 CompRet = ModRet | BinRet | ErrRet
                 ModRet = {ok,ModuleName} | {ok,ModuleName,Warnings}
                 BinRet = {ok,ModuleName,Binary} | {ok,ModuleName,Binary,Warnings}
                 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 behavior of the compiler.

              Returns {ok,ModuleName} if successful, or error if there are errors. 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 compile successfully.
                  This is useful for code generators that want to verify the code that they emit.
                  No  code  is  generated.  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
                  guaranteed 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 generated 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 information. Use
                  encrypted debug information (encrypt_debug_info) to prevent this.

                  For details, see beam_lib(3erl).

                {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(3erl).

                  Warning:  Source  code  can  be  reconstructed  from the debug information. Use
                  encrypted debug information (encrypt_debug_info) to prevent this.

                {debug_info_key,KeyString}:

                {debug_info_key,{Mode,KeyString}}:

                  Includes debug information, but encrypts it  so  that  it  cannot  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
                  information available during testing, yet protecting the source code.

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

                  For details, see beam_lib(3erl).

                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(3erl).

                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 transformations have been
                  performed, in the file <File>.E. No object 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 returned 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 supported since R13B04.

                return:
                  A short form for both return_errors and return_warnings.

                verbose:
                  Causes more verbose information from the compiler, describing what it is doing.

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

                {outdir,Dir}:
                  Sets a new directory for the object code. The current  directory  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 including a file. When
                  encountering an -include or -include_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_transform/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_spawn_compiler_process:
                  By default, all code is compiled in a separate process which is  terminated  at
                  the  end  of  compilation.  However, some tools, like Dialyzer or compilers for
                  other BEAM languages,  may  already  manage  their  own  worker  processes  and
                  spawning an extra process may slow the compilation down. In such scenarios, you
                  can pass this option to stop the compiler from spawning an additional process.

                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 verification 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 option  must  be  used  to  resolve  name
                  clashes  with BIFs auto-imported before R14A, if it is needed to call the local
                  function with the same name as an auto-imported BIF without module 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 earlier), the following
              options   control   what   type   of  warnings  that  are  generated.  Except  from
              {warn_format,Verbosity}, the following 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 number 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 explicitly 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 different 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. Default is to emit a
                  warning if option export_all is also given.

                warn_export_vars:
                  Emits warnings for all implicitly exported  variables  referred  to  after  the
                  primitives  where  they were first defined. By default, the compiler only emits
                  warnings for exported variables referred to in a pattern.

                nowarn_shadow_vars:
                  Turns off  warnings  for  "fresh"  variables  in  functional  objects  or  list
                  comprehensions  with the same name as some already 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 local functions. FAs is a tuple  {Name,Arity}  or  a
                  list of such tuples.

                nowarn_deprecated_function:
                  Turns  off  warnings  for  calls  to  deprecated  functions. Default 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 assembled list of deprecated functions in Erlang/OTP. To do a  more  general
                  check,  the  Xref  tool  can  be  used.  See  also  xref(3erl) 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 compiler to be deprecated.

                nowarn_removed:
                  Turns off warnings for calls to functions that have been removed. Default is to
                  emit warnings for every call to a function known by the compiler to  have  been
                  recently removed from Erlang/OTP.

                {nowarn_removed, ModulesOrMFAs}:
                  Turns  off  warnings  for calls to modules or functions that have been removed.
                  Default is to emit warnings for every call to a function known by the  compiler
                  to have been recently removed from Erlang/OTP.

                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 equivalents. 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, except 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 warnings).

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

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

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

          Note:
              Before  OTP  22,  the option {nowarn_deprecated_function, MFAs} was only recognized
              when   given   in   the   file   with    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.) Starting from OTP  22,  all  options
              that can be given in the file can also be given in the option list.

              For  debugging  of  the  compiler,  or  for  pure  curiosity, the intermediate 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 earliest 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_warnings]).

       forms(Forms, Options) -> CompRet

              Types:

                 Forms = [Form]
                 CompRet = BinRet | ErrRet
                 BinRet = {ok,ModuleName,BinaryOrCode} | {ok,ModuleName,BinaryOrCode,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 options that normally produce a listing  file,  such  as
              'E',  the  internal  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  implicitly 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_COMPILER_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    variable
              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 output_generated/2. Use
       the alternative functions noenv_file/2, noenv_forms/2, or noenv_output_generated/2 if  you
       do  not want the environment 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 preserved, except if  exceptions  are  generated  in  the
       inlined  code.  Exceptions  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 exported (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,  inlining  can  increase
       Beam stack use, which probably is detrimental to performance for recursive functions.

       Inlining  is  never  default.  It  must  be explicitly enabled with a compiler 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 option is given inside a compile  directive  in  an  Erlang
       module, {Name,Arity} 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 allowed 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 specific 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(3erl), erl_id_trans(3erl), erl_lint(3erl), beam_lib(3erl)