Symbol(3p)            User Contributed Perl Documentation           Symbol(3p)



NAME
       Apache::Symbol - Things for symbol things

SYNOPSIS
        use Apache::Symbol ();

        @ISA = qw(Apache::Symbol);

DESCRIPTION
       perlsub/Constant Functions says:

        If you redefine a subroutine which was eligible for inlining you'll get
        a mandatory warning.  (You can use this warning to tell whether or not a
        particular subroutine is considered constant.)  The warning is
        considered severe enough not to be optional because previously compiled
        invocations of the function will still be using the old value of the
        function.

       mandatory warning means there is _no_ way to avoid this warning no
       matter what tricks you pull in Perl.  This is bogus for us mod_perl
       users when restarting the server with PerlFreshRestart on or when
       Apache::StatINC pulls in a module that has changed on disk.

       You can, however, pull some tricks with XS to avoid this warning,
       Apache::Symbol::undef does just that.

ARGUMENTS
       "undef_functions" takes two arguments: "skip" and "only_undef_exports".

       "skip" is a regular expression indicating the function names to skip.

       Use the "only_undef_exports" flag to undef only those functions which
       are listed in @EXPORT, @EXPORT_OK, %EXPORT_TAGS, or @EXPORT_EXTRAS.
       @EXPORT_EXTRAS is not used by the Exporter, it is only exists to
       communicate with "undef_functions".

       As a special case, if none of the EXPORT variables are defined ignore
       "only_undef_exports".  This takes care of trivial modules that don't
       use the Exporter.

ARGUMENTS
       "undef_functions" takes two arguments: "skip" and "only_undef_exports".

       "skip" is a regular expression indicating the function names to skip.

       Use the "only_undef_exports" flag to undef only those functions which
       are listed in @EXPORT, @EXPORT_OK, %EXPORT_TAGS, or @EXPORT_EXTRAS.
       @EXPORT_EXTRAS is not used by the Exporter, it is only exists to
       communicate with "undef_functions".

       As a special case, if none of the EXPORT variables are defined ignore
       "only_undef_exports".  This takes care of trivial modules that don't
       use the Exporter.

PLAYERS
       This module and the undefining of functions is optional, if you wish to
       have this functionality enabled, there are one or more switches you
       need to know about.

       PerlRestartHandler
           Apache::Symbol defines a PerlRestartHandler which can be useful in
           conjuction with "PerlFreshRestart On" as it will avoid subroutine
           redefinition messages.  Configure like so:

            PerlRestartHandler Apache::Symbol

       Apache::Registry
           By placing the SYNOPSIS bit in you script, Apache::Registry will
           undefine subroutines in your script before it is re-compiled to
           avoid "subroutine re-defined" warnings.

       Apache::StatINC
           See Apache::StatINC's docs.

       APACHE_SYMBOL_UNIVERSAL
           If this environment variable is true when Symbol.pm is compiled, it
           will define UNIVERSAL::undef_functions, which means all classes
           will inherit Apache::Symbol::undef_functions.

       Others
           Module such as HTML::Embperl and Apache::ePerl who compile and
           script cache scripts ala Apache::Registry style can use
           "undef_functions" with this bit of code:

               if($package->can('undef_functions')) {
                   $package->undef_functions;
               }

           Where $package is the name of the package in which the script is
           being re-compiled.

SEE ALSO
       perlsub(1), Devel::Symdump(3)

AUTHOR
       Doug MacEachern



perl v5.12.2                      2000-03-03                        Symbol(3p)
