B::Xref(3p) Perl Programmers Reference Guide B::Xref(3p) #
B::Xref(3p) Perl Programmers Reference Guide B::Xref(3p)
NNAAMMEE #
B::Xref - Generates cross reference reports for Perl programs
SSYYNNOOPPSSIISS #
perl -MO=Xref[,OPTIONS] foo.pl
DDEESSCCRRIIPPTTIIOONN #
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 FFiillee section reports on a single file. Each SSuubbrroouuttiinnee 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 PPaacckkaaggee of each variable, subroutine or
format with the special case "(lexicals)" meaning lexical variables. Each
oobbjjeecctt name (implicitly qualified by its containing PPaacckkaaggee) 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 _p_o_d_2_m_a_n 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 mmyy(()) (lexical) variable, iintroduced (first
declared with mmyy(())) 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 mmyy(())) 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 _m_y_p_e_r_l_p_r_o_g_r_a_m to
the file _r_e_p_o_r_t:
$ perl -MO=Xref,-oreport myperlprogram
OOPPTTIIOONNSS #
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.
BBUUGGSS #
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.
AAUUTTHHOORR #
Malcolm Beattie, mbeattie@sable.ox.ac.uk.
perl v5.36.3 2019-02-13 B::Xref(3p)