Ubuntu Manpage: compile - Erlang Compiler

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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

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 with no 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.

Here follows first all elements of Options that in some way control the behavior of
the compiler.

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

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

strong_validation:
Similar to the basic_validation option, no code will be generated, but more
compiler passes will be run to ensure also 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 run-time).

binary:
Causes the compiler to return 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). See the Efficiency Guide for
further information.

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

debug_info:

Include debug information in the form of abstract code (see The Abstract Format
in ERTS User's Guide) in 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 (see below) to prevent this.

See beam_lib(3erl) for details.

{debug_info_key,KeyString}:

{debug_info_key,{Mode,KeyString}}:

Include debug information, but encrypt it, so that it cannot be accessed
without supplying the key. (To give the debug_info option as well is allowed,
but is not necessary.) Using this option is a good way to always have the debug
information available during testing, yet protect the source code.

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

See beam_lib(3erl) for details.

encrypt_debug_info:

Like the debug_info_key option above, except that the key will be read from an
.erlang.crypt file.

See beam_lib(3erl) for details.

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

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

For instance, if one has the following module:

-module(module).

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

Here is the Makefile rule generated by this option:

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

{makedep_output, Output}:
Write generated rule(s) 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}:
Change the name of the rule emitted to Target.

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

makedep_add_missing:
Consider missing headers as generated files and add them to the dependencies.

makedep_phony:
Add 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:
This is a short form for both report_errors and report_warnings.

return_errors:
If this flag is set, then {error,ErrorList,WarningList} is returned when there
are errors.

return_warnings:
If this flag is set, then 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:
This is 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}:
Sets the value of the source, as returned by module_info(compile).

{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}:
Add 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 the i option. 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.

asm:
The input file is expected to be assembler code (default file suffix ".S").
Note that the format of assembler files is not documented, and may change
between releases - this option is primarily for internal debugging use.

no_strict_record_tests:
This option is not recommended.

By default, the generated code for the Record#record_tag.field operation
verifies that the tuple Record is of 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 module erlang,
which resolves BIF name clashes. This option has to be used to resolve name
clashes with BIFs auto-imported before R14A, if one wants to call the local
function with the same name as an auto-imported BIF without module prefix.

Note:
From R14A and forward, the compiler resolves calls without module prefix to local
or imported functions before trying 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}. Example:

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

no_line_info:
Omit line number information in order to produce a slightly smaller output
file.

If warnings are turned on (the report_warnings option described above), the
following options control what type of warnings that will be generated. With the
exception of {warn_format,Verbosity} all options below have two forms; one warn_xxx
form to turn on the warning and one nowarn_xxx form to turn off the warning. In the
description that follows, the form that is used to change the default value is
listed.

{warn_format, Verbosity}:
Causes warnings to be emitted for malformed format strings as arguments to
io:format and similar functions. Verbosity selects the amount of warnings: 0 =
no warnings; 1 = warnings for invalid format strings and incorrect number of
arguments; 2 = warnings also when the validity could not be checked (for
example, when the format string argument is a variable). The default verbosity
is 1. Verbosity 0 can also be selected by the option nowarn_format.

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

Warning:
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 makes a module calling functions clashing
with autoimported BIFs compile with both the old and new compilers, but with
completely different semantics, why the option was removed.

The use of this option has always been strongly discouraged. From OTP R14A and
forward it's 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 will generate a fatal error if used.

Warning:
The use of this option has always been strongly discouraged. From OTP R14A and
forward it's an error to use it.

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

warn_export_all:
Causes a warning to be emitted if the export_all option has also been given.

warn_export_vars:
Causes warnings to be emitted for all implicitly exported variables referred to
after the primitives where they were first defined. No warnings for exported
variables unless they are referred to in some pattern, which is the default,
can be selected by the option nowarn_export_vars.

warn_shadow_vars:
Causes warnings to be emitted for "fresh" variables in functional objects or
list comprehensions with the same name as some already defined variable. The
default is to warn for such variables. No warnings for shadowed variables can
be selected by the option nowarn_shadow_vars.

nowarn_unused_function:
Turns off warnings for unused local functions. By default
(warn_unused_function), warnings are emitted 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 as nowarn_unused_function 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. By default
(warn_deprecated_function), warnings are emitted for every call to a function
known by the compiler to be deprecated. Note that the compiler does not know
about the -deprecated() attribute 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
c:xm/1 function.

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

warn_obsolete_guard:
Causes warnings to be emitted 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. No warnings for calls to old type testing BIFs,
which is the default, can be selected by the option nowarn_obsolete_guard.

warn_unused_import:
Causes warnings to be emitted for unused imported functions. No warnings for
unused imported functions, which is the default, can be selected by the option
nowarn_unused_import.

nowarn_unused_vars:
By default, warnings are emitted for variables which are not used, with the
exception of 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. By default (warn_unused_records),
warnings are emitted 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 will always evaluate to false, and expressions that will always fail (such as
atom+42).

Note that the compiler does not warn for expressions that it does not attempt to
optimize. For instance, the compiler tries to evaluate 1/0, notices that it will
cause an exception and emits a warning. On the other hand, the compiler is silent
about the similar expression X/0; because of the variable in it, the compiler does
not even try to evaluate and therefore it emits no warnings.

Currently, those warnings cannot be disabled (except by disabling all warnings).

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

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

Note also that the {nowarn_unused_function, FAs}, {nowarn_bif_clash, FAs}, and
{nowarn_deprecated_function, MFAs} options are only recognized when given in files.
They are not affected by the warn_unused_function, warn_bif_clash, or
warn_deprecated_function options.

For debugging of the compiler, or for pure curiosity, the intermediate code
generated by each compiler pass can be inspected. A complete list of the options to
produce list files can be printed by typing compile:options() at the Erlang shell
prompt. The options will be printed in 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 below. The file name has been included here as the compiler
uses the Erlang pre-processor epp, which allows the code to be included in other
files. For this reason, it is important to know to which file an error or warning
line number refers.

forms(Forms)

Is the same as forms(File, [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. The option binary is implicit; i.e., no object
code file is produced. Options that would ordinarily produce a listing file, such
as 'E', will instead cause the internal format for that compiler pass (an Erlang
term; usually not a binary) to be returned instead of a binary.

format_error(ErrorDescriptor) -> chars()

Types:

ErrorDescriptor = errordesc()

Uses an ErrorDescriptor and returns a deep list of characters which describes the
error. This function is usually called implicitly when an ErrorInfo structure is
processed. See below.

output_generated(Options) -> true | false

Types:

Options = [term()]

Determines whether the compiler would generate a beam file with the given options.
true means that a beam file would be generated; false means that the compiler would
generate some listing file, return a binary, or merely check the syntax of the
source code.

noenv_file(File, Options) -> CompRet

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

noenv_forms(Forms, Options) -> CompRet

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

noenv_output_generated(Options) -> true | false

Types:

Options = [term()]

Works exactly 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 will be used as is. If it is not a list, it will be put into a list.

       The list will be 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 don't want the environment variable to be consulted (for instance, if you are  calling
       the compiler recursively from inside a parse transform).

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 will be reported as  occurring  in  the  function  the  body  was
       inlined  into.  Also,  function_clause exceptions will be converted to similar case_clause
       exceptions.

       When a function is inlined, the original function will be kept if it is  exported  (either
       by  an  explicit  export or if the export_all option was given) or if not all calls to the
       function were inlined.

       Inlining does not necessarily improve running time. For instance,  inlining  may  increase
       Beam  stack  usage  which  will  probably  be  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  inline  option  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} may be written as Name/Arity.

       Example of explicit inlining:

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

       pi() -> 3.1416.

       Example of implicit inlining:

       -compile(inline).

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

       Example:

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

INLINING OF LIST FUNCTIONS

       The compiler can also inline a variety of list manipulation functions  from  the  stdlib's
       lists module.

       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 the inline_list_funcs option.

       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 above is the standard ErrorInfo structure which is returned from
       all IO modules. It has the following format:

       {ErrorLine, Module, ErrorDescriptor}

       ErrorLine will be the atom none if the error does not correspond to a specific line  (e.g.
       if the source file does not exist).

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

       Module:format_error(ErrorDescriptor)

NAME

DESCRIPTION

EXPORTS

DEFAULT COMPILER OPTIONS

INLINING

INLINING OF LIST FUNCTIONS

PARSE TRANSFORMATIONS

ERROR INFORMATION

SEE ALSO