lfe_abstract_code.erl - Debug Info Provider

Purpose: Provide debug_info callback for Erlang tools (Dialyzer, debugger, cover, xref).

Location: src/lfe_abstract_code.erl Size: 51 LOC, 1.7KB

Module Classification: Integration, tool support

Public API

debug_info(Format, Module, Data, Options) ->
    {ok, Result}
  | {error, Reason}

Erlang compiler callback for debug information. Located at lfe_abstract_code.erl:37-52.

Supported Formats

erlang_v1 - Erlang Abstract Format:

Returns the LFE-generated Erlang AST directly.

core_v1 - Core Erlang:

Converts AST to Core Erlang using compile:noenv_forms/2.

Implementation

debug_info(_Format, _Module, {none, _CompOpts}, _Opts) ->
    {error, missing};  % No debug info stored

debug_info(erlang_v1, _Mod, {AbstrCode, _CompilerOpts}, _Opts) ->
    {ok, AbstrCode};  % Return AST as-is

debug_info(core_v1, _Mod, {AbstrCode, CompilerOpts}, Opts) ->
    % Convert to Core Erlang
    CoreOpts = add_core_returns(delete_reports(CompilerOpts ++ Opts)),
    try compile:noenv_forms(AbstrCode, CoreOpts) of
        {ok, _, Core, _} -> {ok, Core};
        _Error -> {error, failed_conversion}
    catch
        error:_E -> {error, failed_conversion}
    end;

debug_info(_Format, _, _Data, _) ->
    {error, unknown_format}.  % Unknown format requested

Storage in BEAM

Debug Info Chunk:

When compiling with debug info, LFE stores:

{debug_info, {lfe_abstract_code, {AbstractCode, CompilerOpts}}}

This is stored in the BEAM file's debug_info chunk.

Tool Integration

Dialyzer:

Requests erlang_v1 or core_v1 format for type analysis:

{ok, Core} = lfe_abstract_code:debug_info(core_v1, Mod, DebugInfo, [])
% Dialyzer analyzes Core Erlang for types

Debugger:

Requests erlang_v1 for step debugging:

{ok, AST} = lfe_abstract_code:debug_info(erlang_v1, Mod, DebugInfo, [])
% Debugger uses AST for breakpoints, stepping

Cover (Code Coverage):

Requests erlang_v1 for coverage analysis:

{ok, AST} = lfe_abstract_code:debug_info(erlang_v1, Mod, DebugInfo, [])
% Cover instruments AST for coverage tracking

Dependencies

Erlang compiler:

• compile:noenv_forms/2 - Core Erlang conversion

Used By

• Dialyzer
• Erlang debugger
• Cover
• Xref
• Any tool querying debug_info

Special Considerations

Compile Options:

To include debug info:

lfec +debug_info mymodule.lfe

Without +debug_info, tools cannot analyze the module.

Format Evolution:

If Erlang adds new debug_info formats, this module needs updates.

Security:

Debug info includes source-level information. Strip it for production releases:

lfec mymodule.lfe  # No debug info by default