NAME

Devel::Callsite - Get caller return OP address and Perl interpreter context

SYNOPSIS

use Devel::Callsite;
my $site = sub { return callsite() };
printf "OP location: 0x%x\n", $site->(); # prints caller OP location
printf "OP location: 0x%x\n", $site->(); # prints a different OP location


sub foo { return callsite(1) };
sub bar { foo() };
# print this OP location even though it is 2 levels up the call chain.
printf "OP location: 0x%x\n", bar();

print context(), "\n"; # prints the interpreter context, an unsigned number

DESCRIPTION

callsite

$callsite = callsite()
$callsite = callsite($level)

This function returns the the OP address of the caller, a number. It can take an optional integer specifying the number of levels back to get the OP address. If no parameter is given, a value of 0 is used which means to go up one level in the call chain. This behavior is like the built-in function caller.

This value is useful for functions that need to uniquely know where they were called, such as Every::every(); see Every. Or it can be used to pinpoint a location with finer granularity than a line number. In conjunction with an OP tree disassembly you can know exactly where the caller is located in the Perl source.

As of version 0.08, this function will return the expected call site for functions called via DB::sub. (Previously it returned a call site inside the debugger.) If callsite is called from package DB in list context, it will return two numbers. The first is the ordinary return value; the second is the 'true' call site of the function in question, which may be different if DB::sub is in use.

context

$context = context()

This function returns the interpreter context as a number. Using callsite alone to identify the call site is not reliable in programs which may include multiple Perl interpreters, such as when using ithreads. Combining callsite with context gives a unique location.

HISTORY

Ben Morrow conceived this and posted it to perl5-porters. Ted Zlatanov then turned it into a CPAN module which he maintained for the first 3 revisions. Ben also added the level parameter to callsite.

It is currently maintained (or not) by Rocky Bernstein.

SEE ALSO

B::Concise to disassemble the OP tree. Devel::Trepan optionally uses Devel::Callsite to show you exactly where you are stopped inside the debugger.

AUTHORS

Rocky Bernstein <rocky@cpan.org> (current maintainer) Ted Zlatanov <tzz@lifelogs.com> Ben Morrow

LICENSE AND COPYRIGHT

Copyright (C) 2013 Rocky Bernstein <rocky@cpan.org>, Ted Zlatanov, <tzz@lifelogs.com>, Ben Morrow

This program is distributed WITHOUT ANY WARRANTY, including but not limited to the implied warranties of merchantability or fitness for a particular purpose.

The program is free software. You may distribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation (either version 2 or any later version) and the Perl Artistic License as published by O’Reilly Media, Inc. Please open the files named gpl-2.0.txt and Artistic for a copy of these licenses.