NAME

       dialyzer - Dialyzer, a DIscrepancy AnaLYZer for ERlang programs.

DESCRIPTION

       Dialyzer  is a static analysis tool that identifies software discrepancies, such as definite type errors,
       code that has become dead or unreachable because of programming error, and unnecessary tests,  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).

USING DIALYZER FROM THE COMMAND LINE

       Dialyzer has a command-line version for automated use. This section provides a brief description  of  the
       options. The same information can be obtained by writing the following in a shell:

       dialyzer --help

       For  more details about the operation of Dialyzer, see section  Using Dialyzer from the GUI in the User's
       Guide.

       Exit status of the command-line version:

         0:
           No problems were found during the analysis and no warnings were emitted.

         1:
           Problems were found during the analysis.

         2:
           No problems were found during the analysis, but warnings were emitted.

       Usage:

       dialyzer [--add_to_plt] [--apps applications] [--build_plt]
                [--check_plt] [-Ddefine]* [-Dname]* [--dump_callgraph file]
                [--error_location flag] [files_or_dirs] [--fullpath]
                [--get_warnings] [--gui] [--help] [-I include_dir]*
                [--no_check_plt] [--no_indentation] [-o outfile]
                [--output_plt file] [-pa dir]* [--plt plt] [--plt_info]
                [--plts plt*] [--quiet] [-r dirs] [--raw] [--remove_from_plt]
                [--shell] [--src] [--statistics] [--verbose] [--version]
                [-Wwarn]*

   Note:
       * denotes that multiple occurrences of the option are possible.

       Options of the command-line version:

         --add_to_plt:
           The PLT is extended to also include the files specified with -c and -r. Use --plt  to  specify  which
           PLT  to  start  from,  and  --output_plt  to  specify  where to put the PLT. Notice that the analysis
           possibly can include files from the PLT if they depend on the new files. This option only  works  for
           BEAM files.

         --apps applications:
           This option is typically used when building or modifying a PLT as in:

         dialyzer --build_plt --apps erts kernel stdlib mnesia ...

           to  refer conveniently to library applications corresponding to the Erlang/OTP installation. However,
           this option is general and can also be used during analysis to refer to Erlang/OTP applications. File
           or directory names can also be included, as in:

         dialyzer --apps inets ssl ./ebin ../other_lib/ebin/my_module.beam

         --build_plt:
           The  analysis starts from an empty PLT and creates a new one from the files specified with -c and -r.
           This option only works  for  BEAM  files.  To  override  the  default  PLT  location,  use  --plt  or
           --output_plt.

         --check_plt:
           Check the PLT for consistency and rebuild it if it is not up-to-date.

         -Dname (or -Dname=value):
           When analyzing from source, pass the define to Dialyzer. (**)

         --dump_callgraph file:
           Dump  the  call  graph  into the specified file whose format is determined by the filename extension.
           Supported extensions are: raw, dot, and ps. If something else is used as filename extension,  default
           format .raw is used.

         --error_location column | line:
           Use  a pair {Line, Column} or an integer Line to pinpoint the location of warnings. The default is to
           use a pair {Line, Column}. When formatted, the line and the column are separated by a colon.

         files_or_dirs (for backward compatibility also as -c files_or_dirs):
           Use Dialyzer from the command line to detect defects in the specified files or directories containing
           .erl or .beam files, depending on the type of the analysis.

         --fullpath:
           Display the full path names of files for which warnings are emitted.

         --get_warnings:
           Make  Dialyzer emit warnings even when manipulating the PLT. Warnings are only emitted for files that
           are analyzed.

         --gui:
           Use the GUI.

         --help (or -h):
           Print this message and exit.

         -I include_dir:
           When analyzing from source, pass the include_dir to Dialyzer. (**)

         --input_list_file file:
           Analyze the file names that are listed in the specified file (one file name per line).

         --no_check_plt:
           Skip the PLT check when running Dialyzer. This is useful when working with installed PLTs that  never
           change.

         --no_indentation:
           Do not insert line breaks in types, contracts, and Erlang Code when formatting warnings.

         -o outfile (or --output outfile):
           When  using Dialyzer from the command line, send the analysis results to the specified outfile rather
           than to stdout.

         --output_plt file:
           Store the PLT at the specified file after building it.

         -pa dir:
           Include dir in the path for Erlang. This is useful when  analyzing  files  that  have  -include_lib()
           directives.

         --plt plt:
           Use  the  specified  PLT as the initial PLT. If the PLT was built during setup, the files are checked
           for consistency.

         --plt_info:
           Make Dialyzer print information about the PLT and then quit. The PLT can be specified with --plt(s).

         --plts plt*:
           Merge the specified PLTs to create the initial PLT. This requires that the PLTs  are  disjoint  (that
           is, do not have any module appearing in more than one PLT). The PLTs are created in the usual way:

         dialyzer --build_plt --output_plt plt_1 files_to_include
         ...
         dialyzer --build_plt --output_plt plt_n files_to_include

           They can then be used in either of the following ways:

         dialyzer files_to_analyze --plts plt_1 ... plt_n

           or

         dialyzer --plts plt_1 ... plt_n -- files_to_analyze

           Notice the -- delimiter in the second case.

         --quiet (or -q):
           Make Dialyzer a bit more quiet.

         -r dirs:
           Same  as  files_or_dirs,  but  the  specified directories are searched recursively for subdirectories
           containing .erl or .beam files in them, depending on the type of analysis.

         --raw:
           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 example, to filter warnings or to
           output HTML pages).

         --remove_from_plt:
           The information from the files specified with -c and -r is removed from the PLT. Notice that this can
           cause a reanalysis of the remaining dependent files.

         --shell:
           Do not disable the Erlang shell while running the GUI.

         --src:
           Override  the  default,  which is to analyze BEAM files, and analyze starting from Erlang source code
           instead.

         --statistics:
           Print information about the progress of execution (analysis phases, time spent in each, and  size  of
           the relative input).

         --verbose:
           Make Dialyzer a bit more verbose.

         --version (or -v):
           Print the Dialyzer version and some more information and exit.

         -Wwarn:
           A  family  of  options that selectively turn on/off warnings. (For help on the names of warnings, use
           dialyzer -Whelp.) Notice that the options can also be  specified  in  the  file  with  a  -dialyzer()
           attribute. For details, see section Requesting or Suppressing Warnings in Source Files.

   Note:
       **  options  -D and -I work both from the command line and in the Dialyzer GUI; the syntax of defines and
       includes is the same as that used by erlc(1).

       Warning options:

         -Werror_handling (***):
           Include warnings for functions that only return by an exception.

         -Wextra_return (***):
           Warn about functions whose specification includes types that the function cannot return.

         -Wmissing_return (***):
           Warn about functions that return values that are not part of the specification.

         -Wno_behaviours:
           Suppress warnings about behavior callbacks that drift from the published recommended interfaces.

         -Wno_contracts:
           Suppress warnings about invalid contracts.

         -Wno_fail_call:
           Suppress warnings for failing calls.

         -Wno_fun_app:
           Suppress warnings for fun applications that will fail.

         -Wno_improper_lists:
           Suppress warnings for construction of improper lists.

         -Wno_match:
           Suppress warnings for patterns that are unused or cannot match.

         -Wno_missing_calls:
           Suppress warnings about calls to missing functions.

         -Wno_opaque:
           Suppress warnings for violations of opacity of data types.

         -Wno_return:
           Suppress warnings for functions that will never return a value.

         -Wno_undefined_callbacks:
           Suppress warnings about behaviors that have no -callback attributes for their callbacks.

         -Wno_unused:
           Suppress warnings for unused functions.

         -Wunderspecs (***):
           Warn about underspecified functions (the specification is strictly more  allowing  than  the  success
           typing).

         -Wunknown (***):
           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 Dialyzer from Erlang, warnings about unknown functions and types are returned; the default
           is not to return these warnings.

         -Wunmatched_returns (***):
           Include warnings for function calls that ignore a structured return value or do not match against one
           of many possible return values. However, no warnings are included if the possible return values are a
           union of atoms or a union of numbers.

       The following options are also available, but their use is not recommended (they are mostly for  Dialyzer
       developers and internal debugging):

         -Woverspecs (***):
           Warn  about  overspecified  functions  (the  specification is strictly less allowing than the success
           typing).

         -Wspecdiffs (***):
           Warn when the specification is different than the success typing.

   Note:
       *** denotes options that turn on warnings rather than turning them off.

       The following option is not strictly needed as it specifies the default. It is primarily intended  to  be
       used  with  the  -dialyzer  attribute.  For  an example see section Requesting or Suppressing Warnings in
       Source Files.

         -Wno_underspecs:
           Suppress warnings about underspecified functions (the specification is strictly  more  allowing  than
           the success typing).

         -Wno_extra_return:
           Suppress warnings about functions whose specification includes types that the function cannot return.

         -Wno_missing_return:
           Suppress warnings about functions that return values that are not part of the specification.

USING DIALYZER FROM ERLANG

       Dialyzer can be used directly from Erlang. Both the GUI and the command-line versions are also available.
       The options are similar to the ones given from the command line, see section   Using  Dialyzer  from  the
       Command Line.

DEFAULT DIALYZER OPTIONS

       The  (host  operating  system)  environment  variable  ERL_COMPILER_OPTIONS  can  be used to give default
       Dialyzer 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 run/1 or on the command line.

       The list can be retrieved with  compile:env_compiler_options/0.

       Currently the only option used is the error_location option.

REQUESTING OR SUPPRESSING WARNINGS IN SOURCE FILES

       Attribute -dialyzer() 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 f/0, include the following line:

       -dialyzer({nowarn_function, f/0}).

       To turn off warnings for improper lists, add the following line to the source file:

       -dialyzer(no_improper_lists).

       Attribute -dialyzer() is allowed after function declarations. Lists of warning options or  functions  are
       allowed:

       -dialyzer([{nowarn_function, [f/0]}, no_improper_lists]).

       Warning options can be restricted to functions:

       -dialyzer({no_improper_lists, g/0}).

       -dialyzer({[no_return, no_match], [g/0, h/0]}).

       The  warning  option for underspecified functions, -Wunderspecs, can result in useful warnings, but often
       functions with specifications that are strictly more allowing than the success typing  cannot  easily  be
       modified  to  be  less  allowing.  To  turn  off the warning for underspecified function f/0, include the
       following line:

       -dialyzer({no_underspecs, f/0}).

       For help on the warning options,  use  dialyzer  -Whelp.  The  options  are  also  enumerated,  see  type
       warn_option().

   Note:
       Warning option -Wrace_conditions has no effect when set in source files.

       Attribute  -dialyzer()  can also be used for turning on warnings. For example, if a module has been fixed
       regarding unmatched returns, adding the following line can help in assuring that no new unmatched  return
       warnings are introduced:

       -dialyzer(unmatched_returns).

DATA TYPES

       dial_option() =
           {files, [FileName :: file:filename()]} |
           {files_rec, [DirName :: file:filename()]} |
           {defines, [{Macro :: atom(), Value :: term()}]} |
           {from, src_code | byte_code} |
           {init_plt, FileName :: file:filename()} |
           {plts, [FileName :: file:filename()]} |
           {include_dirs, [DirName :: file:filename()]} |
           {output_file, FileName :: file:filename()} |
           {output_plt, FileName :: file:filename()} |
           {check_plt, boolean()} |
           {analysis_type,
            succ_typings | plt_add | plt_build | plt_check | plt_remove} |
           {warnings, [warn_option()]} |
           {get_warnings, boolean()} |
           {error_location, error_location()}

              Option from defaults to byte_code. Options init_plt and plts change the default.

       dial_warn_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_map_construction |
           warn_matching | warn_non_proper_list | warn_not_called |
           warn_opaque | warn_return_no_exit | warn_return_only_exit |
           warn_undefined_callbacks | warn_unknown | warn_umatched_return

       dial_warning() =
           {Tag :: dial_warn_tag(),
            Id :: file_location(),
            Msg :: {atom(), [term()]}}

       error_location() = column | line

              If the value of this option is line, an integer Line is used as Location in messages. If the value
              is column, a pair {Line, Column} is used as Location. The default is column.

       file_location() =
           {File :: file:filename(), Location :: erl_anno:location()}

       warn_option() =
           error_handling | no_behaviours | no_contracts | no_fail_call |
           no_fun_app | no_improper_lists | no_match | no_missing_calls |
           no_opaque | no_return | no_undefined_callbacks |
           no_underspecs | no_unused | underspecs | unknown |
           unmatched_returns | overspecs | specdiffs | extra_return |
           no_extra_return | missing_return | no_missing_return

              See section Warning options for a description of the warning options.

EXPORTS

       format_warning(Warnings) -> string()

              Types:

                 Warnings = dial_warning()

              Get a string from warnings as returned by run/1.

       format_warning(Warnings, Options) -> string()

              Types:

                 Warnings = dial_warning()
                 Options = filename_opt() | [format_option()]
                 format_option() =
                     {indent_opt, boolean()} |
                     {filename_opt, filename_opt()} |
                     {error_location, error_location()}
                 filename_opt() = basename | fullpath

              Get a string from warnings as returned by run/1.

              If indent_opt is set to true (default), line breaks are inserted in types, contracts,  and  Erlang
              code to improve readability.

              If error_location is set to column (default), locations are formatted as Line:Column if the column
              number is available, otherwise locations are formatted as  Line  even  if  the  column  number  is
              available.

       gui() -> ok

       gui(Options) -> ok

              Types:

                 Options = [dial_option()]

              Dialyzer GUI version.

       plt_info(Plt) -> {ok, Result} | {error, Reason}

              Types:

                 Plt = file:filename()
                 Result = [{files, [file:filename()]}]
                 Reason = not_valid | no_such_file | read_error

              Returns information about the specified PLT.

       run(Options) -> Warnings

              Types:

                 Options = [dial_option()]
                 Warnings = [dial_warning()]

              Dialyzer command-line version.