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<img alt="Erlang logo" src="../../../../doc/erlang-logo.png"><br><small><a href="index.html">Reference Manual</a><br><a href="release_notes.html">Release Notes</a><br><a href="../pdf/compiler-6.0.3.pdf">PDF</a><br><a href="../../../../doc/index.html">Top</a></small><p><strong>Compiler</strong><br><strong>Reference Manual</strong><br><small>Version 6.0.3</small></p>
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<!-- refpage --><center><h1>compile</h1></center>
<h3>MODULE</h3>
<div class="REFBODY">compile</div>
<h3>MODULE SUMMARY</h3>
<div class="REFBODY">Erlang Compiler</div>
<h3>DESCRIPTION</h3>
<div class="REFBODY"><p>
<p>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.
</p>
</p></div>
<h3>EXPORTS</h3>
<p><a name="file-1"><span class="bold_code">file(File)</span></a><br></p>
<div class="REFBODY"><p>
<p>Is the same as
<span class="code">file(File, [verbose,report_errors,report_warnings])</span>.
</p>
</p></div>
<p><a name="file-2"><span class="bold_code">file(File, Options) -> CompRet</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">CompRet = ModRet | BinRet | ErrRet</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">ModRet = {ok,ModuleName} | {ok,ModuleName,Warnings}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">BinRet = {ok,ModuleName,Binary} | {ok,ModuleName,Binary,Warnings}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">ErrRet = error | {error,Errors,Warnings}</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Compiles the code in the file <span class="code">File</span>, which is an
Erlang source code file without the <span class="code">.erl</span> extension.
<span class="code">Options</span> determine the behavior of the compiler.</p>
<p>Returns <span class="code">{ok,ModuleName}</span> if successful, or <span class="code">error</span>
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.</p>
<p><a name="type-option"></a>Available options:</p>
<dl>
<dt><strong><span class="code">basic_validation</span></strong></dt>
<dd>
<p>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 <span class="code">erl_lint</span> module (such as warnings for unused
variables and functions) are also returned.</p>
<p>Use option <span class="code">strong_validation</span> to generate all
warnings that the compiler would generate.</p>
</dd>
<dt><strong><span class="code">strong_validation</span></strong></dt>
<dd>
<p>Similar to option <span class="code">basic_validation</span>. 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).</p>
</dd>
<dt><strong><span class="code">binary</span></strong></dt>
<dd>
<p>The compiler returns the object code in a
binary instead of creating an object file. If successful,
the compiler returns <span class="code">{ok,ModuleName,Binary}</span>.</p>
</dd>
<dt><strong><span class="code">bin_opt_info</span></strong></dt>
<dd>
<p>The compiler will emit informational warnings about binary
matching optimizations (both successful and unsuccessful).
For more information, see the section about
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','doc/efficiency_guide','binaryhandling.html#bin_opt_info');">bin_opt_info</a></span>
in the Efficiency Guide.</p>
</dd>
<dt><strong><span class="code">compressed</span></strong></dt>
<dd>
<p>The compiler will compress the generated object code,
which can be useful for embedded systems.</p>
</dd>
<dt><strong><span class="code">debug_info</span></strong></dt>
<dd>
<a name="debug_info"></a>
<p>Includes debug information in the form of abstract code
(see
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','absform.html');">The Abstract Format</a></span>
in ERTS User's Guide) in the compiled beam module. Tools
such as <span class="code">Debugger</span>, <span class="code">Xref</span>, and <span class="code">Cover</span> require
the debug information to be included.</p>
<p><strong>Warning</strong>: Source code can be reconstructed from
the debug information. Use encrypted debug information
(<span class="code">encrypt_debug_info</span>) to prevent this.</p>
<p>For details, see
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','beam_lib.html#debug_info');">beam_lib(3)</a></span>.</p>
</dd>
<dt><strong><span class="code">{debug_info_key,KeyString}</span></strong></dt>
<dd></dd>
<dt><strong><span class="code">{debug_info_key,{Mode,KeyString}}</span></strong></dt>
<dd>
<a name="debug_info_key"></a>
<p>Includes debug information, but encrypts it so that it
cannot be accessed without supplying the key. (To give
option <span class="code">debug_info</span> 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.</p>
<p><span class="code">Mode</span> is the type of crypto algorithm to be used
for encrypting the debug information. The default
(and currently the only) type is <span class="code">des3_cbc</span>.</p>
<p>For details, see
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','beam_lib.html#debug_info');">beam_lib(3)</a></span>.</p>
</dd>
<dt><strong><span class="code">encrypt_debug_info</span></strong></dt>
<dd>
<a name="encrypt_debug_info"></a>
<p>Similar to the <span class="code">debug_info_key</span> option, but
the key is read from an <span class="code">.erlang.crypt</span> file.
</p>
<p>For details, see
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','beam_lib.html#debug_info');">beam_lib(3)</a></span>.</p>
</dd>
<dt><strong><span class="code">makedep</span></strong></dt>
<dd>
<p>Produces a Makefile rule to track headers dependencies.
No object file is produced.
</p>
<p>By default, this rule is written to
<span class="code"><File>.Pbeam</span>. However, if option
<span class="code">binary</span> is set, nothing is written and the rule is
returned in <span class="code">Binary</span>.
</p>
<p>For example, if you have the following module:
</p>
<div class="example"><pre>
-module(module).
-include_lib("eunit/include/eunit.hrl").
-include("header.hrl").</pre></div>
<p>The Makefile rule generated by this option looks as follows:
</p>
<div class="example"><pre>
module.beam: module.erl \
/usr/local/lib/erlang/lib/eunit/include/eunit.hrl \
header.hrl</pre></div>
</dd>
<dt><strong><span class="code">{makedep_output, Output}</span></strong></dt>
<dd>
<p>Writes generated rules to <span class="code">Output</span> instead of the
default <span class="code"><File>.Pbeam</span>. <span class="code">Output</span>
can be a filename or an <span class="code">io_device()</span>. To write to
stdout, use <span class="code">standard_io</span>. However, if <span class="code">binary</span>
is set, nothing is written to <span class="code">Output</span> and the
result is returned to the caller with
<span class="code">{ok, ModuleName, Binary}</span>.
</p>
</dd>
<dt><strong><span class="code">{makedep_target, Target}</span></strong></dt>
<dd>
<p>Changes the name of the rule emitted to <span class="code">Target</span>.
</p>
</dd>
<dt><strong><span class="code">makedep_quote_target</span></strong></dt>
<dd>
<p>Characters in <span class="code">Target</span> special to make(1) are quoted.
</p>
</dd>
<dt><strong><span class="code">makedep_add_missing</span></strong></dt>
<dd>
<p>Considers missing headers as generated files and adds them to the
dependencies.
</p>
</dd>
<dt><strong><span class="code">makedep_phony</span></strong></dt>
<dd>
<p>Adds a phony target for each dependency.
</p>
</dd>
<dt><strong><span class="code">'P'</span></strong></dt>
<dd>
<p>Produces a listing of the parsed code, after preprocessing
and parse transforms, in the file
<span class="code"><File>.P</span>. No object file is produced.
</p>
</dd>
<dt><strong><span class="code">'E'</span></strong></dt>
<dd>
<p>Produces a listing of the code, after all source code
transformations have been performed, in the file
<span class="code"><File>.E</span>. No object file is produced.
</p>
</dd>
<dt><strong><span class="code">'S'</span></strong></dt>
<dd>
<p>Produces a listing of the assembler code in the file
<span class="code"><File>.S</span>. No object file is produced.
</p>
</dd>
<dt><strong><span class="code">report_errors/report_warnings</span></strong></dt>
<dd>
<p>Causes errors/warnings to be printed as they occur.</p>
</dd>
<dt><strong><span class="code">report</span></strong></dt>
<dd>
<p>A short form for both <span class="code">report_errors</span> and
<span class="code">report_warnings</span>.</p>
</dd>
<dt><strong><span class="code">return_errors</span></strong></dt>
<dd>
<p>If this flag is set,
<span class="code">{error,ErrorList,WarningList}</span> is returned when
there are errors.</p>
</dd>
<dt><strong><span class="code">return_warnings</span></strong></dt>
<dd>
<p>If this flag is set, an extra field, containing
<span class="code">WarningList</span>, is added to the tuples returned on
success.</p>
</dd>
<dt><strong><span class="code">warnings_as_errors</span></strong></dt>
<dd>
<p>Causes warnings to be treated as errors. This option is supported
since R13B04.</p>
</dd>
<dt><strong><span class="code">return</span></strong></dt>
<dd>
<p>A short form for both <span class="code">return_errors</span> and
<span class="code">return_warnings</span>.</p>
</dd>
<dt><strong><span class="code">verbose</span></strong></dt>
<dd>
<p>Causes more verbose information from the compiler,
describing what it is doing.</p>
</dd>
<dt><strong><span class="code">{source,FileName}</span></strong></dt>
<dd>
<p>Sets the value of the source, as returned by
<span class="code">module_info(compile)</span>.</p>
</dd>
<dt><strong><span class="code">{outdir,Dir}</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">export_all</span></strong></dt>
<dd>
<p>Causes all functions in the module to be exported.</p>
</dd>
<dt><strong><span class="code">{i,Dir}</span></strong></dt>
<dd>
<p>Adds <span class="code">Dir</span> to the list of directories to be searched
when including a file. When encountering an
<span class="code">-include</span> or <span class="code">-include_lib</span> directive,
the compiler searches for header files in the following
directories:</p>
<ul>
<li>
<p><span class="code">"."</span>, the current working directory of
the file server</p>
</li>
<li>
<p>The base name of the compiled file</p>
</li>
<li>
<p>The directories specified using option <span class="code">i</span>;
the directory specified last is searched first</p>
</li>
</ul>
</dd>
<dt><strong><span class="code">{d,Macro}</span></strong></dt>
<dd></dd>
<dt><strong><span class="code">{d,Macro,Value}</span></strong></dt>
<dd>
<p>Defines a macro <span class="code">Macro</span> to have the value
<span class="code">Value</span>. <span class="code">Macro</span> is of type atom, and <span class="code">Value</span> can be any term.
The default <span class="code">Value</span> is <span class="code">true</span>.</p>
</dd>
<dt><strong><span class="code">{parse_transform,Module}</span></strong></dt>
<dd>
<p>Causes the parse transformation function
<span class="code">Module:parse_transform/2</span> to be applied to the
parsed code before the code is checked for errors.</p>
</dd>
<dt><strong><span class="code">from_asm</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">from_core</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">no_strict_record_tests</span></strong></dt>
<dd>
<p>This option is not recommended.</p>
<p>By default, the generated code for
operation <span class="code">Record#record_tag.field</span> verifies that
the tuple <span class="code">Record</span> has the correct size for
the record, and that the first element is the tag
<span class="code">record_tag</span>. Use this option to omit
the verification code.</p>
</dd>
<dt><strong><span class="code">no_error_module_mismatch</span></strong></dt>
<dd>
<p>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).</p>
</dd>
<dt><strong><span class="code">{no_auto_import,[{F,A}, ...]}</span></strong></dt>
<dd>
<p>Makes the function <span class="code">F/A</span> no longer being
auto-imported from the <span class="code">erlang</span> 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.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>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 <span class="code">erlang</span> module prefix in the call, not
<span class="code">{ no_auto_import,[{F,A}, ...]}</span>.</p>
</p></div>
</div>
<p>If this option is written in the source code, as a
<span class="code">-compile</span> directive, the syntax <span class="code">F/A</span> can be used instead
of <span class="code">{F,A}</span>, for example:</p>
<div class="example"><pre>-compile({no_auto_import,[error/1]}).</pre></div>
</dd>
<dt><strong><span class="code">no_auto_import</span></strong></dt>
<dd>
<p>Do not auto-import any functions from <span class="code">erlang</span> module.</p>
</dd>
<dt><strong><span class="code">no_line_info</span></strong></dt>
<dd>
<p>Omits line number information to produce a slightly
smaller output file.
</p>
</dd>
</dl>
<p>If warnings are turned on (option <span class="code">report_warnings</span>
described earlier), the following options control what type of
warnings that are generated.
<a name="erl_lint_options"></a>
Except from <span class="code">{warn_format,Verbosity}</span>, the following options
have two forms:</p>
<ul>
<li>A <span class="code">warn_xxx</span> form, to turn on the warning.</li>
<li>A <span class="code">nowarn_xxx</span> form, to turn off the warning.</li>
</ul>
<p>In the descriptions that follow, the form that is used to change
the default value are listed.</p>
<dl>
<dt><strong><span class="code">{warn_format, Verbosity}</span></strong></dt>
<dd>
<p>Causes warnings to be emitted for malformed format
strings as arguments to <span class="code">io:format</span> and similar
functions.</p>
<p><span class="code">Verbosity</span> selects the number of warnings:</p>
<ul>
<li>
<span class="code">0</span> = No warnings</li>
<li>
<span class="code">1</span> = Warnings for invalid format strings and incorrect
number of arguments</li>
<li>
<span class="code">2</span> = Warnings also when the validity cannot
be checked, for example, when the format string argument is a
variable.</li>
</ul>
<p>The default verbosity is <span class="code">1</span>. Verbosity <span class="code">0</span> can
also be selected by option <span class="code">nowarn_format</span>.</p>
</dd>
<dt><strong><span class="code">nowarn_bif_clash</span></strong></dt>
<dd>
<p>This option is removed, it generates a fatal error if used.</p>
<div class="warning">
<div class="label">Warning</div>
<div class="content"><p>
<p>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 <span class="code">nowarn_bif_clash</span> 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.</p>
<p>The use of this option has always been discouraged.
As from R14A, it is an error to use it.</p>
<p>To resolve BIF clashes, use explicit module names or the
<span class="code">{no_auto_import,[F/A]}</span> compiler directive.</p>
</p></div>
</div>
</dd>
<dt><strong><span class="code">{nowarn_bif_clash, FAs}</span></strong></dt>
<dd>
<p>This option is removed, it generates a fatal error if used.</p>
<div class="warning">
<div class="label">Warning</div>
<div class="content"><p>
<p>The use of this option has always been discouraged.
As from R14A, it is an error to use it.</p>
<p>To resolve BIF clashes, use explicit module names or the
<span class="code">{no_auto_import,[F/A]}</span> compiler directive.</p>
</p></div>
</div>
</dd>
<dt><strong><span class="code">warn_export_all</span></strong></dt>
<dd>
<p>Emits a warning if option <span class="code">export_all</span> is also given.</p>
</dd>
<dt><strong><span class="code">warn_export_vars</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">nowarn_shadow_vars</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">nowarn_unused_function</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">{nowarn_unused_function, FAs}</span></strong></dt>
<dd>
<p>Turns off warnings for unused local functions like
<span class="code">nowarn_unused_function</span> does, but only for the mentioned
local functions. <span class="code">FAs</span> is a tuple <span class="code">{Name,Arity}</span>
or a list of such tuples.</p>
</dd>
<dt><strong><span class="code">nowarn_deprecated_function</span></strong></dt>
<dd>
<p>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 <span class="code">-deprecated()</span>, but uses an
assembled list of deprecated functions in Erlang/OTP. To
do a more general check, the <span class="code">Xref</span> tool can be used.
See also
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','tools','xref.html#deprecated_function');">xref(3)</a></span>
and the function
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','tools','xref.html#m-1');">xref:m/1</a></span>, also
accessible through the function
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','c.html#xm-1');">c:xm/1</a></span>.</p>
</dd>
<dt><strong><span class="code">{nowarn_deprecated_function, MFAs}</span></strong></dt>
<dd>
<p>Turns off warnings for calls to deprecated functions like
<span class="code">nowarn_deprecated_function</span> does, but only for
the mentioned functions. <span class="code">MFAs</span> is a tuple
<span class="code">{Module,Name,Arity}</span> or a list of such tuples.</p>
</dd>
<dt><strong><span class="code">nowarn_deprecated_type</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">warn_obsolete_guard</span></strong></dt>
<dd>
<p>Emits warnings for calls to old type testing BIFs,
such as <span class="code">pid/1</span> and <span class="code">list/1</span>. See the
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','doc/reference_manual','expressions.html#guards');">Erlang Reference Manual</a></span>
for a complete list of type testing BIFs and their old
equivalents. Default is to emit no warnings for calls to
old type testing BIFs.</p>
</dd>
<dt><strong><span class="code">warn_unused_import</span></strong></dt>
<dd>
<p>Emits warnings for unused imported functions.
Default is to emit no warnings for unused imported functions.</p>
</dd>
<dt><strong><span class="code">nowarn_unused_vars</span></strong></dt>
<dd>
<p>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.</p>
</dd>
<dt><strong><span class="code">nowarn_unused_record</span></strong></dt>
<dd>
<p>Turns off warnings for unused record types. Default is to
emit warnings for unused locally defined record types.</p>
</dd>
</dl>
<p>Another class of warnings is generated by the compiler
during optimization and code generation. They warn about
patterns that will never match (such as <span class="code">a=b</span>), guards
that always evaluate to false, and expressions that
always fail (such as <span class="code">atom+42</span>).</p>
<p>Those warnings cannot be disabled (except by
disabling all warnings).</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>The compiler does not warn for expressions that it
does not attempt to optimize. For example, the compiler tries
to evaluate <span class="code">1/0</span>, detects that it will cause an
exception, and emits a warning. However,
the compiler is silent about the similar expression,
<span class="code">X/0</span>, because of the variable in it. Thus, the compiler does
not even try to evaluate and therefore it emits no warnings.</p>
</p></div>
</div>
<div class="warning">
<div class="label">Warning</div>
<div class="content"><p>
<p>The absence of warnings does not mean that
there are no remaining errors in the code.</p>
</p></div>
</div>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>All options, except the include path
(<span class="code">{i,Dir}</span>), can also be given in the file with attribute
<span class="code">-compile([Option,...])</span>.
Attribute <span class="code">-compile()</span> is allowed after the function
definitions.</p>
</p></div>
</div>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>The options <span class="code">{nowarn_unused_function, FAs}</span>,
<span class="code">{nowarn_bif_clash, FAs}</span>, and
<span class="code">{nowarn_deprecated_function, MFAs}</span> are only
recognized when given in files. They are not affected by
options <span class="code">warn_unused_function</span>, <span class="code">warn_bif_clash</span>, or
<span class="code">warn_deprecated_function</span>.</p>
</p></div>
</div>
<p>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 <span class="code">compile:options()</span> 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.</p>
<p>Unrecognized options are ignored.</p>
<p>Both <span class="code">WarningList</span> and <span class="code">ErrorList</span> have
the following format:</p>
<div class="example"><pre>
[{FileName,[ErrorInfo]}].</pre></div>
<p><span class="code">ErrorInfo</span> is described later in this section.
The filename is included here, as the compiler uses the
Erlang pre-processor <span class="code">epp</span>, which allows the code to be
included in other files. It is therefore important to know to
<strong>which</strong> file the line number of an error or a warning refers.
</p>
</p></div>
<p><a name="forms-1"><span class="bold_code">forms(Forms)</span></a><br></p>
<div class="REFBODY"><p>
<p>Is the same as
<span class="code">forms(File, [verbose,report_errors,report_warnings])</span>.
</p>
</p></div>
<p><a name="forms-2"><span class="bold_code">forms(Forms, Options) -> CompRet</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">Forms = [Form]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">CompRet = BinRet | ErrRet</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">BinRet = {ok,ModuleName,BinaryOrCode} | {ok,ModuleName,BinaryOrCode,Warnings}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">BinaryOrCode = binary() | term()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">ErrRet = error | {error,Errors,Warnings}</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Analogous to <span class="code">file/1</span>, but takes a list of forms (in
the Erlang abstract format representation) as first argument.
Option <span class="code">binary</span> 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.</p>
</p></div>
<p><a name="format_error-1"><span class="bold_code">format_error(ErrorDescriptor) -> chars()</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">ErrorDescriptor = errordesc()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Uses an <span class="code">ErrorDescriptor</span> and returns a deep list of
characters that describes the error. This function is
usually called implicitly when an <span class="code">ErrorInfo</span> structure
(described in section
<span class="bold_code"><a href="#error_information">Error Information</a></span>) is processed.</p>
</p></div>
<p><a name="output_generated-1"><span class="bold_code">output_generated(Options) -> true | false</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">Options = [term()]</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Determines whether the compiler generates a <span class="code">beam</span>
file with the given options. <span class="code">true</span> means that a <span class="code">beam</span>
file is generated. <span class="code">false</span> means that the compiler
generates some listing file, returns a binary, or merely
checks the syntax of the source code.</p>
</p></div>
<p><a name="noenv_file-2"><span class="bold_code">noenv_file(File, Options) -> CompRet</span></a><br></p>
<div class="REFBODY"><p>
<p>Works like <span class="bold_code"><a href="#file-2">file/2</a></span>,
except that the environment variable <span class="code">ERL_COMPILER_OPTIONS</span>
is not consulted.</p>
</p></div>
<p><a name="noenv_forms-2"><span class="bold_code">noenv_forms(Forms, Options) -> CompRet</span></a><br></p>
<div class="REFBODY"><p>
<p>Works like <span class="bold_code"><a href="#forms-2">forms/2</a></span>,
except that the environment variable <span class="code">ERL_COMPILER_OPTIONS</span>
is not consulted.</p>
</p></div>
<p><a name="noenv_output_generated-1"><span class="bold_code">noenv_output_generated(Options) -> true | false</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">Options = [term()]</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Works like
<span class="bold_code"><a href="#output_generated-1">output_generated/1</a></span>,
except that the environment variable <span class="code">ERL_COMPILER_OPTIONS</span>
is not consulted.</p>
</p></div>
<h3><a name="idp307911196">Default Compiler Options</a></h3>
<div class="REFBODY">
<p>The (host operating system) environment variable
<span class="code">ERL_COMPILER_OPTIONS</span> 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.</p>
<p>The list is appended to any options given to
<span class="bold_code"><a href="#file-2">file/2</a></span>,
<span class="bold_code"><a href="#forms-2">forms/2</a></span>, and
<span class="bold_code"><a href="#output_generated-1">output_generated/2</a></span>.
Use the alternative functions
<span class="bold_code"><a href="#noenv_file-2">noenv_file/2</a></span>,
<span class="bold_code"><a href="#noenv_forms-2">noenv_forms/2</a></span>, or
<span class="bold_code"><a href="#noenv_output_generated-1">noenv_output_generated/2</a></span>
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.</p>
</div>
<h3><a name="idp307915068">Inlining</a></h3>
<div class="REFBODY">
<p>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,
<span class="code">function_clause</span> exceptions are converted to similar
<span class="code">case_clause</span> exceptions.</p>
<p>When a function is inlined, the original function is
kept if it is exported (either by an explicit export or if the
option <span class="code">export_all</span> was given) or if not all calls to the
function are inlined.</p>
<p>Inlining does not necessarily improve running time.
For example, inlining can increase Beam stack use, which
probably is detrimental to performance for recursive functions.
</p>
<p>Inlining is never default. It must be explicitly enabled with a
compiler option or a <span class="code">-compile()</span> attribute in the source
module.</p>
<p>To enable inlining, either use the option <span class="code">inline</span> to
let the compiler decide which functions to inline, or
<span class="code">{inline,[{Name,Arity},...]}</span> to have the compiler inline
all calls to the given functions. If the option is given inside
a <span class="code">compile</span> directive in an Erlang module, <span class="code">{Name,Arity}</span>
can be written as <span class="code">Name/Arity</span>.</p>
<p>Example of explicit inlining:</p>
<div class="example"><pre>
-compile({inline,[pi/0]}).
pi() -> 3.1416.
</pre></div>
<p>Example of implicit inlining:</p>
<div class="example"><pre>
-compile(inline).</pre></div>
<p>The option <span class="code">{inline_size,Size}</span> controls how large functions
that are allowed to be inlined. Default is <span class="code">24</span>, which
keeps the size of the inlined code roughly the same as
the un-inlined version (only relatively small functions are
inlined).</p>
<p>Example:</p>
<div class="example"><pre>
%% Aggressive inlining - will increase code size.
-compile(inline).
-compile({inline_size,100}).</pre></div>
</div>
<h3><a name="idp308092404">Inlining of List Functions</a></h3>
<div class="REFBODY">
<p>The compiler can also inline various list manipulation functions
from the module <span class="code">list</span> in <span class="code">STDLIB</span>.</p>
<p>This feature must be explicitly enabled with a compiler option or a
<span class="code">-compile()</span> attribute in the source module.</p>
<p>To enable inlining of list functions, use option <span class="code">inline_list_funcs</span>.</p>
<p>The following functions are inlined:</p>
<ul>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#all-2');">lists:all/2</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#any-2');">lists:any/2</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#foreach-2');">lists:foreach/2</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#map-2');">lists:map/2</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#flatmap-2');">lists:flatmap/2</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#filter-2');">lists:filter/2</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#foldl-3');">lists:foldl/3</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#foldr-3');">lists:foldr/3</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#mapfoldl-3');">lists:mapfoldl/3</a></span></li>
<li><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','lists.html#mapfoldr-3');">lists:mapfoldr/3</a></span></li>
</ul>
</div>
<h3><a name="idp308023068">Parse Transformations</a></h3>
<div class="REFBODY">
<p>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.</p>
</div>
<h3><a name="idp308024220">Error Information</a></h3>
<div class="REFBODY">
<a name="error_information"></a>
<p>The <span class="code">ErrorInfo</span> mentioned earlier is the standard
<span class="code">ErrorInfo</span> structure, which is returned from all I/O modules.
It has the following format:</p>
<div class="example"><pre>
{ErrorLine, Module, ErrorDescriptor}</pre></div>
<p><span class="code">ErrorLine</span> is the atom <span class="code">none</span> if the error does
not correspond to a specific line, for example, if the source file does
not exist.</p>
<p>A string describing the error is obtained with the following
call:</p>
<div class="example"><pre>
Module:format_error(ErrorDescriptor)</pre></div>
</div>
<h3><a name="idp308027236">See Also</a></h3>
<div class="REFBODY">
<p>
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','epp.html');">epp(3)</a></span>,
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','erl_id_trans.html');">erl_id_trans(3)</a></span>,
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','erl_lint.html');">erl_lint(3)</a></span>,
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','stdlib','beam_lib.html');">beam_lib(3)</a></span>
</p>
</div>
</div>
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