The Dialyzer, a DIscrepancy AnalYZer for ERlang programs

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).

Read more about Dialyzer and about how to use it from the GUI in Dialyzer User's Guide.

Using the Dialyzer from the command line

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

      dialyzer --help

in a shell. Please refer to the GUI description for more details on the operation of Dialyzer.

The exit status of the command line version is:

      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.


   dialyzer [--help] [--version] [--shell] [--quiet] [--verbose]
		[-pa dir]* [--plt plt] [-Ddefine]* [-I include_dir]* 
		[--output_plt file] [-Wwarn]* [--src] 
		[-c applications] [-r applications] [-o outfile]
		[--build_plt] [--add_to_plt] [--remove_from_plt]
		[--check_plt] [--no_check_plt] [--plt_info] [--get_warnings]


-c applications(or --command-line applications)
use Dialyzer from the command line (no GUI) to detect defects in the specified applications (directories or .erl or .beam files)
-r applications
same as -c only that directories are searched recursively for subdirectories containing .erl or .beam files (depending on the type of analysis)
-o outfile(or --output outfile)
when using Dialyzer from the command line, send the analysis results in the specified outfile rather than in stdout
override the default, which is to analyze debug compiled BEAM bytecode, and analyze starting from Erlang source code instead
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).
-Dname(or -Dname=value)
when analyzing from source, pass the define to Dialyzer (**)
-I include_dir
when analyzing from source, pass the include_dir to Dialyzer (**)
-pa dir
Include dir in the path for Erlang. Useful when analyzing files that have -include_lib() directives.
--output_plt file
Store the PLT at the specified location after building it.
--plt plt
Use the specified plt as the initial persistent lookup table.
a family of option which selectively turn on/off warnings. (for help on the names of warnings use dialyzer -Whelp)
do not disable the Erlang shell while running the GUI
--version (or -v)
prints the Dialyzer version and some more information and exits
--help (or -h)
prints this message and exits
--quiet (or -q)
makes Dialyzer a bit more quiet
makes Dialyzer a bit more verbose
Only checks if the initial PLT is up to date and rebuilds it if this is not the case
--no_check_plt (or -n)
Skip the PLT integrity check when running Dialyzer. Useful when working with installed PLTs that never change.
The analysis starts from an empty PLT and creates a new one from the files specified with -c and -r. Only works for beam files. Use --plt or --output_plt to override the default PLT location.
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. Note that the analysis might include files from the PLT if they depend on the new files. This option only works with beam files.
The information from the files specified with -c and -r is removed from the PLT. Note that this may cause a re-analysis of the remaining dependent files.
Makes Dialyzer emit warnings even when manipulating the PLT. Only emits warnings for files that are actually analyzed. The default is to not emit any warnings when manipulating the PLT. This option has no effect when performing a normal analysis.


* denotes that multiple occurrences of these options are possible.

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

Warning options:

Suppress warnings for functions of no return.
Suppress warnings for unused functions.
Suppress warnings for construction of improper lists.
Suppress warnings for fun applications that will fail.
Suppress warnings for patterns that are unused or cannot match.
Include warnings for functions that only return by means of an exception.
Include warnings for function calls which ignore a structured return value or do not match against one of many possible return value(s).
Warn about underspecified functions (the -spec is strictly more allowing than the success typing)
Warn about overspecified functions (the -spec is strictly less allowing than the success typing)
Warn when the -spec is different than the success typing


*** These are options that turn on warnings rather than turning them off.

Using the Dialyzer from Erlang

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.


gui() -> ok | {error, Msg}

gui(OptList) -> ok | {error, Msg}

  • OptList -- see below

Dialyzer GUI version.

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
         | {include_dirs,   [DirName : string()]} 
         | {output_file,    FileName : string()}
         | {output_plt,     FileName :: string()}
         | {analysis_type,  'success_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_fail_call
         | error_handling
         | unmatched_returns
         | overspecs
         | underspecs
         | specdiffs

run(OptList) -> Warnings

  • OptList -- see gui/0,1
  • Warnings -- see below

Dialyzer command line version.

Warnings :: [{Tag, Id, Msg}]
Tag : 'warn_return_no_exit' | 'warn_return_only_exit'
    | 'warn_not_called' | 'warn_non_proper_list'
    | 'warn_fun_app' | 'warn_matching'
    | 'warn_failing_call' | 'warn_contract_types'
    | 'warn_contract_syntax' | 'warn_contract_not_equal'
    | 'warn_contract_subtype' | 'warn_contract_supertype'
Id = {File :: string(), Line :: integer()}
Msg = msg() -- Undefined

format_warning(Msg) -> string()

  • Msg = {Tag, Id, msg()} -- See run/1

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

plt_info(string()) -> {'ok', [{atom(), any()}]} | {'error', atom()}

Returns information about the specified plt.