Symbol(3) User Contributed Perl Documentation Symbol(3)NAMEApache::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 mat-
ter 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 commu-
nicate 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 commu-
nicate 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 ALSOperlsub(1), Devel::Symdump(3)AUTHOR
Doug MacEachern
perl v5.8.8 2007-03-30 Symbol(3)