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B::Xref(3perl) Perl Programmers Reference Guide B::Xref(3perl)
NAME
B::Xref - Generates cross reference reports for Perl programs
SYNOPSIS
perl -MO=Xref[,OPTIONS] foo.pl
DESCRIPTION
The B::Xref module is used to generate a cross reference listing of all definitions and
uses of variables, subroutines and formats in a Perl program. It is implemented as a
backend for the Perl compiler.
The report generated is in the following format:
File filename1
Subroutine subname1
Package package1
object1 line numbers
object2 line numbers
...
Package package2
...
Each File section reports on a single file. Each Subroutine section reports on a single
subroutine apart from the special cases "(definitions)" and "(main)". These report,
respectively, on subroutine definitions found by the initial symbol table walk and on the
main part of the program or module external to all subroutines.
The report is then grouped by the Package of each variable, subroutine or format with the
special case "(lexicals)" meaning lexical variables. Each object name (implicitly
qualified by its containing Package) includes its type character(s) at the beginning where
possible. Lexical variables are easier to track and even included dereferencing
information where possible.
The "line numbers" are a comma separated list of line numbers (some preceded by code
letters) where that object is used in some way. Simple uses aren't preceded by a code
letter. Introductions (such as where a lexical is first defined with "my") are indicated
with the letter "i". Subroutine and method calls are indicated by the character "&".
Subroutine definitions are indicated by "s" and format definitions by "f".
For instance, here's part of the report from the pod2man program that comes with Perl:
Subroutine clear_noremap
Package (lexical)
$ready_to_print i1069, 1079
Package main
$& 1086
$. 1086
$0 1086
$1 1087
$2 1085, 1085
$3 1085, 1085
$ARGV 1086
%HTML_Escapes 1085, 1085
This shows the variables used in the subroutine "clear_noremap". The variable
$ready_to_print is a my() (lexical) variable, introduced (first declared with my()) on
line 1069, and used on line 1079. The variable $& from the main package is used on 1086,
and so on.
A line number may be prefixed by a single letter:
i Lexical variable introduced (declared with my()) for the first time.
& Subroutine or method call.
s Subroutine defined.
r Format defined.
The most useful option the cross referencer has is to save the report to a separate file.
For instance, to save the report on myperlprogram to the file report:
$ perl -MO=Xref,-oreport myperlprogram
OPTIONS
Option words are separated by commas (not whitespace) and follow the usual conventions of
compiler backend options.
"-oFILENAME"
Directs output to "FILENAME" instead of standard output.
"-r" Raw output. Instead of producing a human-readable report, outputs a line in
machine-readable form for each definition/use of a variable/sub/format.
"-d" Don't output the "(definitions)" sections.
"-D[tO]"
(Internal) debug options, probably only useful if "-r" included. The "t" option
prints the object on the top of the stack as it's being tracked. The "O" option
prints each operator as it's being processed in the execution order of the
program.
BUGS
Non-lexical variables are quite difficult to track through a program. Sometimes the type
of a non-lexical variable's use is impossible to determine. Introductions of non-lexical
non-scalars don't seem to be reported properly.
AUTHOR
Malcolm Beattie, mbeattie AT sable.uk.
perl v5.34.0 2023-11-23 B::Xref(3perl)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
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