1B::Xref(3pm) Perl Programmers Reference Guide B::Xref(3pm)
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6 B::Xref - Generates cross reference reports for Perl programs
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9 perl -MO=Xref[,OPTIONS] foo.pl
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12 The B::Xref module is used to generate a cross reference listing of all
13 definitions and uses of variables, subroutines and formats in a Perl
14 program. It is implemented as a backend for the Perl compiler.
15 The report generated is in the following format:
17 File filename1
19 Subroutine subname1
20 Package package1
21 object1 line numbers
22 object2 line numbers
23 ...
24 Package package2
25 ...
26 Each File section reports on a single file. Each Subroutine section
28 reports on a single subroutine apart from the special cases
29 "(definitions)" and "(main)". These report, respectively, on subroutine
30 definitions found by the initial symbol table walk and on the main part
31 of the program or module external to all subroutines.
32 The report is then grouped by the Package of each variable, subroutine
34 or format with the special case "(lexicals)" meaning lexical variables.
35 Each object name (implicitly qualified by its containing Package)
36 includes its type character(s) at the beginning where possible. Lexical
37 variables are easier to track and even included dereferencing
38 information where possible.
39 The "line numbers" are a comma separated list of line numbers (some
41 preceded by code letters) where that object is used in some way.
42 Simple uses aren't preceded by a code letter. Introductions (such as
43 where a lexical is first defined with "my") are indicated with the
44 letter "i". Subroutine and method calls are indicated by the character
45 "&". Subroutine definitions are indicated by "s" and format
46 definitions by "f".
47 For instance, here's part of the report from the pod2man program that
49 comes with Perl:
50 Subroutine clear_noremap
52 Package (lexical)
53 $ready_to_print i1069, 1079
54 Package main
55 $& 1086
56 $. 1086
57 $0 1086
58 $1 1087
59 $2 1085, 1085
60 $3 1085, 1085
61 $ARGV 1086
62 %HTML_Escapes 1085, 1085
63 This shows the variables used in the subroutine "clear_noremap". The
65 variable $ready_to_print is a my() (lexical) variable, introduced
66 (first declared with my()) on line 1069, and used on line 1079. The
67 variable $& from the main package is used on 1086, and so on.
68 A line number may be prefixed by a single letter:
70 i Lexical variable introduced (declared with my()) for the first
72 time.
73 & Subroutine or method call.
75 s Subroutine defined.
77 r Format defined.
79 The most useful option the cross referencer has is to save the report
81 to a separate file. For instance, to save the report on myperlprogram
82 to the file report:
83 $ perl -MO=Xref,-oreport myperlprogram
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87 Option words are separated by commas (not whitespace) and follow the
88 usual conventions of compiler backend options.
89 "-oFILENAME"
91 Directs output to "FILENAME" instead of standard output.
92 "-r" Raw output. Instead of producing a human-readable report,
94 outputs a line in machine-readable form for each definition/use
95 of a variable/sub/format.
96 "-d" Don't output the "(definitions)" sections.
98 "-D[tO]"
100 (Internal) debug options, probably only useful if "-r"
101 included. The "t" option prints the object on the top of the
102 stack as it's being tracked. The "O" option prints each
103 operator as it's being processed in the execution order of the
104 program.
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107 Non-lexical variables are quite difficult to track through a program.
108 Sometimes the type of a non-lexical variable's use is impossible to
109 determine. Introductions of non-lexical non-scalars don't seem to be
110 reported properly.
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113 Malcolm Beattie, mbeattie@sable.ox.ac.uk.
114perl v5.30.1 2019-11-29 B::Xref(3pm)