NAME

Paranoid::Debug - Trace message support for paranoid programs

VERSION

$Id: lib/Paranoid/Debug.pm, 2.08 2020/12/31 12:10:06 acorliss Exp $

SYNOPSIS

  use Paranoid::Debug;

  PDEBUG        = 1;
  PDMAXINDENT   = 40;
  PDPREFIX      = sub { scalar localtime };
  pdebug("starting program", 1);
  foo();

  sub foo {
    pdebug("entering foo()", 2);
    pIn();

    pdebug("someting happened!", 2);

    pOut();
    pdebug("leaving w/rv: $rv", 2):
  }

  pderror("error msg");

DESCRIPTION

The purpose of this module is to provide a useful framework to produce debugging output. With this module you can assign a level of detail to pdebug statements, and they'll only be displayed to STDERR when PDEBUG is set to that level or higher. This allows you to have your program produce varying levels of debugging output.

Using the pIn and pOut functions at the beginning and end of each function will cause debugging output to be indented appropriately so you can visually see the level of recursion.

NOTE: All modules within the Paranoid framework use this module. Their debug levels range from 9 and up. You should use 1 - 8 for your own modules or code.

IMPORT LISTS

This module exports the following symbols by default:

    PDEBUG pdebug pIn pOut

The following specialized import lists also exist:

    List        Members
    --------------------------------------------------------
    constants   PDEBUG1 PDEBUG2 PDEBUG3 PDEBUG4 PDEBUG5 
                PDEBUG6 PDEBUG7 PDEBUG8
    all         @defaults @constants 
                pderror PDPREFIX PDLEVEL1 PDLEVEL2 
                PDLEVEL3 PDLEVEL4 PDMAXINDENT

CONSTANTS

PDEBUG1 - PDEBUG8

There are eight constants exported by default for use by developers that allow for up to eight levels of diagnostic output. None of these levels are used by internal Paranoid code, they are reserved for use by third parties.

PDLEVEL1 - PDLEVEL4

These constants are not intended for use by other modules, rather the exist for the internal debug levels used by all Paranoid::* modules.

SUBROUTINES/METHODS

PDEBUG

PDEBUG is an lvalue subroutine which is initially set to 0, but can be set to any positive integer. The higher the number the more pdebug statements are printed.

PDPREFIX

PDPREFIX is an lvalue subroutine that contants a code reference to a subroutine that returns an appropriate prefix for debug messages. The default subroutine prints an indented string (indented according to depth on the call stack) that prints the process PID, debug level, and the current routine/or method that pdebug was called in.

PDMAXINDENT

PDMAXINDENT is an lvalue subroutine which is initially set to 60, but can be set to any integer. This controls the max indentation of the debug messages. Obviously, it wouldn't help to indent a debug message by a hundred columns on an eighty column terminal just because your stack depth gets that deep.

PDPREFIX

PDPREFIX is also an lvalue subroutine and is set by default to a code reference that returns as a string the standard prefix for debug messages:

  [PID - DLEVEL] Subroutine:

Assigning another reference to a subroutine or string can override this behavior. The only argument that will be passed to any such routine will be the name of the calling subroutine.

pderror

  pderror("error msg");

This function prints the passed message to STDERR.

pdebug

  pdebug("debug statement", 3);
  pdebug("debug statement: %s %2d %.3f", 3, @values);

This function is called with one mandatory argument (the string to be printed), and an optional integer. This integer is compared against PDEBUG and the debug statement is printed if PDEBUG is equal to it or higher.

The return value is always the debug statement itself. This allows for a single statement to produce debug output and set variables. For instance:

    Paranoid::ERROR = pdebug("Something bad happened!", 3);

As an added benefit you can pass a printf template along with their values and they will be handled appropriately. String values passed as undef will be replaced with the literal string "undef".

One deviation from printf allows you to specify a placeholder which can gobble up any number of extra arguments while still performing the "undef" substitution:

    pdebug("I was passed these values: %s", 3, @values);

  pIn();

This function causes all subsequent pdebug messages to be indented by one additional space.

pOut

  pOut();

This function causes all subsequent pdebug messages to be indented by one less space.

DEPENDENCIES

Paranoid

BUGS AND LIMITATIONS

pderror (and by extension, pdebug) will generate errors if STDERR is closed elsewhere in the program.

AUTHOR

Arthur Corliss (corliss@digitalmages.com)

LICENSE AND COPYRIGHT

This software is free software. Similar to Perl, you can redistribute it and/or modify it under the terms of either:

  a)     the GNU General Public License
         <https://www.gnu.org/licenses/gpl-1.0.html> as published by the 
         Free Software Foundation <http://www.fsf.org/>; either version 1
         <https://www.gnu.org/licenses/gpl-1.0.html>, or any later version
         <https://www.gnu.org/licenses/license-list.html#GNUGPL>, or
  b)     the Artistic License 2.0
         <https://opensource.org/licenses/Artistic-2.0>,

subject to the following additional term: No trademark rights to "Paranoid" have been or are conveyed under any of the above licenses. However, "Paranoid" may be used fairly to describe this unmodified software, in good faith, but not as a trademark.