Apache::Symbol - Things for symbol things
use Apache::Symbol ();
@ISA = qw(Apache::Symbol);
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.
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.
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.
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.
perlsub(1), Devel::Symdump(3)
Doug MacEachern
