focal (3) Paranoid::Debug.3pm.gz

NAME

       Paranoid::Debug - Trace message support for paranoid programs

VERSION

       $Id: lib/Paranoid/Debug.pm, 2.07 2019/01/30 18:25:27 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.

   EXPORT TARGETS
       Only PDEBUG, pdebug, pIn, and pOut are exported by default.  All other functions and constants can be
       exported with the :all tag set.

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.

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.

   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
         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 licensed under the same terms as Perl, itself.  Please see http://dev.perl.org/licenses/
       for more information.

       (c) 2005 - 2017, Arthur Corliss (corliss@digitalmages.com)