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<erlref>
  <header>
    <copyright>
      <year>2006</year><year>2015</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>dialyzer</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
  </header>
  <module>dialyzer</module>
  <modulesummary>The Dialyzer, a DIscrepancy AnalYZer for ERlang programs</modulesummary>
  <description>
    <p>The Dialyzer is a static analysis tool that identifies software
    discrepancies such as definite type errors, code which has become
    dead or unreachable due to some programming error, unnecessary
    tests, etc. in single Erlang modules or entire (sets of)
    applications. Dialyzer starts its analysis from either
    debug-compiled BEAM bytecode or from Erlang source code. The file
    and line number of a discrepancy is reported along with an
    indication of what the discrepancy is about. Dialyzer bases its
    analysis on the concept of success typings which allows for sound
    warnings (no false positives).</p>
    <p>Read more about Dialyzer and about how to use it from the GUI
    in <seealso marker="dialyzer_chapter">Dialyzer User's
    Guide</seealso>.</p>
  </description>

  <section>
    <title>Using the Dialyzer from the command line</title>
    <p>Dialyzer also has a command line version for automated use. Below is a
      brief description of the list of its options. The same information can
      be obtained by writing</p>
    <code type="none">
      dialyzer --help</code>
    <p>in a shell. Please refer to the GUI description for more details on
      the operation of Dialyzer.</p>
    <p>The exit status of the command line version is:</p>
    <code type="none">
      0 - No problems were encountered during the analysis and no
          warnings were emitted.
      1 - Problems were encountered during the analysis.
      2 - No problems were encountered, but warnings were emitted.</code>
    <p>Usage:</p>
    <code type="none">
       dialyzer [--help] [--version] [--shell] [--quiet] [--verbose]
		[-pa dir]* [--plt plt] [--plts plt*] [-Ddefine]*
                [-I include_dir]* [--output_plt file] [-Wwarn]* [--raw]
                [--src] [--gui] [files_or_dirs] [-r dirs]
                [--apps applications] [-o outfile]
		[--build_plt] [--add_to_plt] [--remove_from_plt]
		[--check_plt] [--no_check_plt] [--plt_info] [--get_warnings]
                [--dump_callgraph file] [--no_native] [--fullpath]
                [--statistics] [--no_native_cache]</code>
    <p>Options:</p>
    <taglist>
      <tag><c><![CDATA[files_or_dirs]]></c> (for backwards compatibility also
        as: <c><![CDATA[-c files_or_dirs]]></c>)</tag>
      <item>Use Dialyzer from the command line to detect defects in the
        specified files or directories containing <c><![CDATA[.erl]]></c> or
         <c><![CDATA[.beam]]></c> files, depending on the type of the
         analysis.</item>
      <tag><c><![CDATA[-r dirs]]></c></tag>
      <item>Same as the previous but the specified directories are searched
        recursively for subdirectories containing <c><![CDATA[.erl]]></c> or
        <c><![CDATA[.beam]]></c> files in them, depending on the type of
        analysis.</item>
      <tag><c><![CDATA[--apps applications]]></c></tag>
      <item>Option typically used when building or modifying a plt as in:
        <code type="none">
           dialyzer --build_plt --apps erts kernel stdlib mnesia ...</code>
        to conveniently refer to library applications corresponding to the
        Erlang/OTP installation. However, the option is general and can also
        be used during analysis in order to refer to Erlang/OTP applications.
        In addition, file or directory names can also be included, as in:
        <code type="none">
           dialyzer --apps inets ssl ./ebin ../other_lib/ebin/my_module.beam</code></item>
      <tag><c><![CDATA[-o outfile]]></c> (or
        <c><![CDATA[--output outfile]]></c>)</tag>
      <item>When using Dialyzer from the command line, send the analysis
        results to the specified outfile rather than to stdout.</item>
      <tag><c><![CDATA[--raw]]></c></tag>
      <item>When using Dialyzer from the command line, output the raw analysis
        results (Erlang terms) instead of the formatted result. The raw format
        is easier to post-process (for instance, to filter warnings or to
        output HTML pages).</item>
      <tag><c><![CDATA[--src]]></c></tag>
      <item>Override the default, which is to analyze BEAM files, and
        analyze starting from Erlang source code instead.</item>
      <tag><c><![CDATA[-Dname]]></c> (or <c><![CDATA[-Dname=value]]></c>)</tag>
      <item>When analyzing from source, pass the define to Dialyzer. (**)</item>
      <tag><c><![CDATA[-I include_dir]]></c></tag>
      <item>When analyzing from source, pass the <c><![CDATA[include_dir]]></c>
        to Dialyzer. (**)</item>
      <tag><c><![CDATA[-pa dir]]></c></tag>
      <item>Include <c><![CDATA[dir]]></c> in the path for Erlang (useful when
        analyzing files that have <c><![CDATA['-include_lib()']]></c>
        directives).</item>
      <tag><c><![CDATA[--output_plt file]]></c></tag>
      <item>Store the plt at the specified file after building it.</item>
      <tag><c><![CDATA[--plt plt]]></c></tag>
      <item>Use the specified plt as the initial plt (if the plt was built
        during setup the files will be checked for consistency).</item>
      <tag><c><![CDATA[--plts plt*]]></c></tag>
      <item>Merge the specified plts to create the initial plt -- requires
        that the plts are disjoint (i.e., do not have any module
        appearing in more than one plt).
        The plts are created in the usual way:
        <code type="none">
           dialyzer --build_plt --output_plt plt_1 files_to_include
           ...
           dialyzer --build_plt --output_plt plt_n files_to_include</code>
        and then can be used in either of the following ways:
        <code type="none">
           dialyzer files_to_analyze --plts plt_1 ... plt_n</code>
        or:
        <code type="none">
           dialyzer --plts plt_1 ... plt_n -- files_to_analyze</code>
        (Note the -- delimiter in the second case)</item>
      <tag><c><![CDATA[-Wwarn]]></c></tag>
      <item>A family of options which selectively turn on/off warnings
        (for help on the names of warnings use
        <c><![CDATA[dialyzer -Whelp]]></c>).
        Note that the options can also be given in the file with a
        <c>-dialyzer()</c> attribute. See <seealso
        marker="#suppression">Requesting or Suppressing Warnings in
        Source Files</seealso> below for details.</item>
      <tag><c><![CDATA[--shell]]></c></tag>
      <item>Do not disable the Erlang shell while running the GUI.</item>
      <tag><c><![CDATA[--version]]></c> (or <c><![CDATA[-v]]></c>)</tag>
      <item>Print the Dialyzer version and some more information and
        exit.</item>
      <tag><c><![CDATA[--help]]></c> (or <c><![CDATA[-h]]></c>)</tag>
      <item>Print this message and exit.</item>
      <tag><c><![CDATA[--quiet]]></c> (or <c><![CDATA[-q]]></c>)</tag>
      <item>Make Dialyzer a bit more quiet.</item>
      <tag><c><![CDATA[--verbose]]></c></tag>
      <item>Make Dialyzer a bit more verbose.</item>
      <tag><c><![CDATA[--statistics]]></c></tag>
      <item>Prints information about the progress of execution (analysis phases,
      time spent in each and size of the relative input).</item>
      <tag><c><![CDATA[--build_plt]]></c></tag>
      <item>The analysis starts from an empty plt and creates a new one from
        the files specified with <c><![CDATA[-c]]></c> and
        <c><![CDATA[-r]]></c>. Only works for beam files. Use
        <c><![CDATA[--plt]]></c> or <c><![CDATA[--output_plt]]></c> to
        override the default plt location.</item>
       <tag><c><![CDATA[--add_to_plt]]></c></tag>
       <item>The plt is extended to also include the files specified with
         <c><![CDATA[-c]]></c> and <c><![CDATA[-r]]></c>. Use
         <c><![CDATA[--plt]]></c> to specify which plt to start from,
         and <c><![CDATA[--output_plt]]></c> to specify where to put the plt.
         Note that the analysis might include files from the plt if they depend
         on the new files. This option only works with beam files.</item>
       <tag><c><![CDATA[--remove_from_plt]]></c></tag>
       <item>The information from the files specified with
         <c><![CDATA[-c]]></c> and <c><![CDATA[-r]]></c> is removed
         from the plt. Note that this may cause a re-analysis of the remaining
         dependent files.</item>
       <tag><c><![CDATA[--check_plt]]></c></tag>
       <item>Check the plt for consistency and rebuild it if it is not
         up-to-date.</item>
       <tag><c><![CDATA[--no_check_plt]]></c></tag>
       <item>Skip the plt check when running Dialyzer. Useful when working with
         installed plts that never change.</item>
       <tag><c><![CDATA[--plt_info]]></c></tag>
       <item>Make Dialyzer print information about the plt and then quit. The
         plt can be specified with <c><![CDATA[--plt(s)]]></c>.</item>
       <tag><c><![CDATA[--get_warnings]]></c></tag>
       <item>Make Dialyzer emit warnings even when manipulating the plt.
         Warnings are only emitted for files that are actually analyzed.</item>
       <tag><c><![CDATA[--dump_callgraph file]]></c></tag>
       <item>Dump the call graph into the specified file whose format is
         determined by the file name extension. Supported extensions are: raw,
         dot, and ps. If something else is used as file name extension, default
         format '.raw' will be used.</item>
       <tag><c><![CDATA[--no_native]]></c> (or <c><![CDATA[-nn]]></c>)</tag>
       <item>Bypass the native code compilation of some key files that Dialyzer
         heuristically performs when dialyzing many files; this avoids the
         compilation time but it may result in (much) longer analysis
         time.</item>
       <tag><c><![CDATA[--no_native_cache]]></c></tag>
       <item>By default, Dialyzer caches the results of native compilation in the
         <c>$XDG_CACHE_HOME/erlang/dialyzer_hipe_cache</c> directory.
         <c>XDG_CACHE_HOME</c> defaults to <c>$HOME/.cache</c>.
         Use this option to disable caching.</item>
       <tag><c><![CDATA[--fullpath]]></c></tag>
       <item>Display the full path names of files for which warnings are emitted.</item>
       <tag><c><![CDATA[--gui]]></c></tag>
       <item>Use the GUI.</item>
    </taglist>
    <note>
      <p>* denotes that multiple occurrences of these options are possible.</p>
      <p>** options <c><![CDATA[-D]]></c> and <c><![CDATA[-I]]></c> work both from command-line and in the Dialyzer GUI;
        the syntax of defines and includes is the same as that used by <c><![CDATA[erlc]]></c>.</p>
    </note>
    <p>Warning options:</p>
    <taglist>
      <tag><c><![CDATA[-Wno_return]]></c></tag>
      <item>Suppress warnings for functions that will never return a
        value.</item>
      <tag><c><![CDATA[-Wno_unused]]></c></tag>
      <item>Suppress warnings for unused functions.</item>
      <tag><c><![CDATA[-Wno_improper_lists]]></c></tag>
      <item>Suppress warnings for construction of improper lists.</item>
      <tag><c><![CDATA[-Wno_fun_app]]></c></tag>
      <item>Suppress warnings for fun applications that will fail.</item>
      <tag><c><![CDATA[-Wno_match]]></c></tag>
      <item>Suppress warnings for patterns that are unused or cannot
       match.</item>
      <tag><c><![CDATA[-Wno_opaque]]></c></tag>
      <item>Suppress warnings for violations of opaqueness of data types.</item>
      <tag><c><![CDATA[-Wno_fail_call]]></c></tag>
      <item>Suppress warnings for failing calls.</item>
      <tag><c><![CDATA[-Wno_contracts]]></c></tag>
      <item>Suppress warnings about invalid contracts.</item>
      <tag><c><![CDATA[-Wno_behaviours]]></c></tag>
      <item>Suppress warnings about behaviour callbacks which drift from the
       published recommended interfaces.</item>
      <tag><c><![CDATA[-Wno_missing_calls]]></c></tag>
      <item>Suppress warnings about calls to missing functions.</item>
      <tag><c><![CDATA[-Wno_undefined_callbacks]]></c></tag>
      <item>Suppress warnings about behaviours that have no
        <c>-callback</c> attributes for their callbacks.</item>
      <tag><c><![CDATA[-Wunmatched_returns]]></c>***</tag>
      <item>Include warnings for function calls which ignore a structured return
        value or do not match against one of many possible return
        value(s).</item>
      <tag><c><![CDATA[-Werror_handling]]></c>***</tag>
      <item>Include warnings for functions that only return by means of an
       exception.</item>
      <tag><c><![CDATA[-Wrace_conditions]]></c>***</tag>
      <item>Include warnings for possible race conditions. Note that the
      analysis that finds data races performs intra-procedural data flow analysis
      and can sometimes explode in time. Enable it at your own risk.
      </item>
      <tag><c><![CDATA[-Wunderspecs]]></c>***</tag>
      <item>Warn about underspecified functions
      (the -spec is strictly more allowing than the success typing).</item>
      <tag><c><![CDATA[-Wunknown]]></c>***</tag>
      <item>Let warnings about unknown functions and types affect the
      exit status of the command line version. The default is to ignore
      warnings about unknown functions and types when setting the exit
      status. When using the Dialyzer from Erlang, warnings about unknown
      functions and types are returned; the default is not to return
      these warnings.</item>
    </taglist>
    <p>The following options are also available but their use is not
      recommended: (they are mostly for Dialyzer developers and internal
      debugging)</p>
    <taglist>
      <tag><c><![CDATA[-Woverspecs]]></c>***</tag>
      <item>Warn about overspecified functions
      (the -spec is strictly less allowing than the success typing).</item>
      <tag><c><![CDATA[-Wspecdiffs]]></c>***</tag>
      <item>Warn when the -spec is different than the success typing.</item>
    </taglist>
    <note>
      <p>*** Identifies options that turn on warnings rather than
      turning them off.</p>
    </note>
  </section>

  <section>
    <title>Using the Dialyzer from Erlang</title>
    <p>You can also use Dialyzer directly from Erlang. Both the GUI and the
      command line versions are available. The options are similar to the ones
      given from the command line, so please refer to the sections above for
      a description of these.</p>
  </section>

  <section>
    <marker id="suppression"></marker>
    <title>Requesting or Suppressing Warnings in Source Files</title>
    <p>
      The <c>-dialyzer()</c> attribute can be used for turning off
      warnings in a module by specifying functions or warning options.
      For example, to turn off all warnings for the function
      <c>f/0</c>, include the following line:
    </p>
<code type="none">
-dialyzer({nowarn_function, f/0}).
</code>
    <p>To turn off warnings for improper lists, add the following line
      to the source file:
    </p>
<code type="none">
-dialyzer(no_improper_lists).
</code>
    <p>The <c>-dialyzer()</c> attribute is allowed after function
    declarations. Lists of warning options or functions are allowed:
    </p>
<code type="none">
-dialyzer([{nowarn_function, [f/0]}, no_improper_lists]).
</code>
    <p>
      Warning options can be restricted to functions:
    </p>
<code type="none">
-dialyzer({no_improper_lists, g/0}).
</code>
<code type="none">
-dialyzer({[no_return, no_match], [g/0, h/0]}).
</code>
    <p>
      For help on the warning options use <c>dialyzer -Whelp</c>. The
      options are also enumerated <seealso
      marker="#gui/1">below</seealso> (<c>WarnOpts</c>).
    </p>
    <note>
      <p>
        The <c>-dialyzer()</c> attribute is not checked by the Erlang
              Compiler, but by the Dialyzer itself.
      </p>
    </note>
    <note>
      <p>
        The warning option <c>-Wrace_conditions</c> has no effect when
        set in source files.
      </p>
    </note>
    <p>
      The <c>-dialyzer()</c> attribute can also be used for turning on
      warnings. For instance, if a module has been fixed regarding
      unmatched returns, adding the line
    </p>
<code type="none">
-dialyzer(unmatched_returns).
</code>
    <p>
      can help in assuring that no new unmatched return warnings are
      introduced.
    </p>
  </section>

  <funcs>
    <func>
      <name>gui() -> ok | {error, Msg}</name>
      <name>gui(OptList) -> ok | {error, Msg}</name>
      <fsummary>Dialyzer GUI version</fsummary>
      <type>
        <v>OptList -- see below</v>
      </type>
      <desc>
        <p>Dialyzer GUI version.</p>
        <code type="none">
OptList  :: [Option]
Option   :: {files,          [Filename :: string()]}
          | {files_rec,      [DirName :: string()]}
          | {defines,        [{Macro :: atom(), Value :: term()}]}
          | {from,           src_code | byte_code}   %% Defaults to byte_code
          | {init_plt,       FileName :: string()}   %% If changed from default
          | {plts,           [FileName :: string()]} %% If changed from default
          | {include_dirs,   [DirName :: string()]}
          | {output_file,    FileName :: string()}
          | {output_plt,     FileName :: string()}
          | {check_plt,      boolean()},
          | {analysis_type,  'succ_typings' |
                             'plt_add' |
                             'plt_build' |
                             'plt_check' |
                             'plt_remove'}
          | {warnings,       [WarnOpts]}
          | {get_warnings,   bool()}

WarnOpts :: no_return
          | no_unused
          | no_improper_lists
          | no_fun_app
          | no_match
          | no_opaque
          | no_fail_call
          | no_contracts
          | no_behaviours
          | no_undefined_callbacks
          | unmatched_returns
          | error_handling
          | race_conditions
          | overspecs
          | underspecs
          | specdiffs
          | unknown</code>
      </desc>
    </func>
    <func>
      <name>run(OptList) -> Warnings</name>
      <fsummary>Dialyzer command line version</fsummary>
      <type>
        <v>OptList -- see gui/0,1</v>
        <v>Warnings -- see below </v>
      </type>
      <desc>
        <p>Dialyzer command line version.</p>
        <code type="none">
Warnings :: [{Tag, Id, Msg}]
Tag :: 'warn_behaviour'
     | 'warn_bin_construction'
     | 'warn_callgraph'
     | 'warn_contract_not_equal'
     | 'warn_contract_range'
     | 'warn_contract_subtype'
     | 'warn_contract_supertype'
     | 'warn_contract_syntax'
     | 'warn_contract_types'
     | 'warn_failing_call'
     | 'warn_fun_app'
     | 'warn_matching'
     | 'warn_non_proper_list'
     | 'warn_not_called'
     | 'warn_opaque'
     | 'warn_race_condition'
     | 'warn_return_no_exit'
     | 'warn_return_only_exit'
     | 'warn_umatched_return'
     | 'warn_undefined_callbacks'
     | 'warn_unknown'
Id = {File :: string(), Line :: integer()}
Msg = msg() -- Undefined</code>
      </desc>
    </func>
    <func>
      <name>format_warning(Msg) -> string()</name>
      <fsummary>Get the string version of a warning message.</fsummary>
      <type>
        <v>Msg = {Tag, Id, msg()} -- See run/1</v>
      </type>
      <desc>
        <p>Get a string from warnings as returned by dialyzer:run/1.</p>
      </desc>
    </func>
    <func>
      <name>plt_info(string()) -> {'ok', [{atom(), any()}]} | {'error', atom()}</name>
      <fsummary>Returns information about the specified plt.</fsummary>
      <desc>
        <p>Returns information about the specified plt.</p>
      </desc>
    </func>
  </funcs>
</erlref>
