B::Generate(3pm)

1B::Generate(3)        User Contributed Perl Documentation       B::Generate(3)
2
3
4

NAME

6       B::Generate - Create your own op trees.
7

SYNOPSIS

9           use B::Generate;
10           # Do nothing, slowly.
11           CHECK {
12               my $null = new B::OP("null",0);
13               my $enter = new B::OP("enter",0);
14               my $cop = new B::COP(0, "hiya", 0);
15               my $leave = new B::LISTOP("leave", 0, $enter, $null);
16               $leave->children(3);
17               $enter->sibling($cop);
18               $enter->next($cop);
19               $cop->sibling($null);
20               $null->next($leave);
21               $cop->next($leave);
22
23               # Tell Perl where to find our tree.
24               B::main_root($leave);
25               B::main_start($enter);
26           }
27

WARNING

29       This module will create segmentation faults if you don't know how to
30       use it properly. Further warning: sometimes I don't know how to use it
31       properly.
32
33       There are lots of other methods and utility functions, but they are not
34       documented here. This is deliberate, rather than just through laziness.
35       You are expected to have read the Perl and XS sources to this module
36       before attempting to do anything with it.
37

DESCRIPTION

39       The "B" module allows you to examine the Perl op tree at runtime, in
40       Perl space; it's the basis of the Perl compiler.  But what it doesn't
41       let you do is manipulate that op tree: it won't let you create new ops,
42       or modify old ones. Now you can.
43
44       Well, if you're intimately familiar with Perl's internals, you can.
45
46       "B::Generate" turns "B"'s accessor methods into get-set methods.
47       Hence, instead of merely saying
48
49           $op2 = $op->next;
50
51       you can now say
52
53           $op->next($op2);
54
55       to set the next op in the chain. It also adds constructor methods to
56       create new ops. This is where it gets really hairy.
57
58           new B::OP     ( type, flags )
59           new B::UNOP   ( type, flags, first )
60           new B::BINOP  ( type, flags, first, last )
61           new B::LOGOP  ( type, flags, first, other )
62           new B::LISTOP ( type, flags, first, last )
63           new B::SVOP   ( type, flags, sv )
64           new B::COP    ( flags, name, first )
65
66       In all of the above constructors, "type" is either a numeric value
67       representing the op type (62 is the addition operator in certain perl
68       versions, for instance) or the name of the op. ("add")
69
70       Incidentally, if you know about custom ops and have registed them
71       properly with the interpreter, you can create custom ops by name: "new
72       B::OP("mycustomop",0)", or whatever.
73
74       "first", "last" and "other" are ops to be attached to the current op;
75       these should be "B::OP" objects. If you haven't created the ops yet,
76       don't worry; give a false value, and fill them in later:
77
78           $x = new B::UNOP("negate", 0, undef);
79           # ... create some more ops ...
80           $x->first($y);
81
82       In addition, one may create a new "nextstate" operator with
83
84           newstate B::op ( flags, label, op)
85
86       in the same manner as "B::COP::new" - this will also, however, add the
87       "lineseq" op.
88
89       Finally, you can set the main root and the starting op by passing ops
90       to the "B::main_root" and "B::main_start" functions.
91
92       This module can obviously be used for all sorts of fun and
93       optimizational purposes. One example will be in conjuction with source
94       filters; have your source filter parse an input file in a foreign
95       language, create an op tree for it and get Perl to execute it. Then
96       email me and tell me how you did it.  And why.
97
98   OTHER METHODS
99       B::SVOP->sv()
100          Returns the SV value instead of the "B::SV" object. For instance:
101
102              $b_sv = $svop->sv;
103              if ($b_sv->sv == 3) {
104                  print "SVOP's SV has an IV of 3\n"
105              }
106
107          But to set the SV you need a proper B::SV object.
108
109       $op->dump
110          Runs "Perl_op_dump" on an op; this is roughly equivalent to
111          "B::Debug", but not quite.
112
113       $b_sv->dump
114          Runs "Perl_sv_dump" on an SV; this is exactly equivalent to
115          Devel::Peek::dump($b_sv->sv)
116
117       $b_op->linklist
118          Sets the "op_next" pointers in the tree in correct execution order,
119          overwriting the old "next" pointers. You need to do this once you've
120          created an op tree for execution, unless you've carefully threaded
121          it together yourself.
122
123       $b_op->scope
124          Create a surrounding scope for the b_op, "parenthesize" it.
125
126          Creates on OPf_PARENS (already parenthesized by the parser) a full
127          lineseq, enter, b_op, leave sequence.
128
129          Otherwise just scope, b_op.
130
131       B::SVOP->new_svrv ( type, flags, sv )
132          Similar to B::SVOP->new ( type, flags, sv ), it just creates a new
133          SVOP with an attached sv as SvRV to the given sv.
134
135       $cv->NEW_with_start (root, start)
136          Clone the "cv" with new root and start ops. Note that contrary to
137          "cv_clone", the PADLIST and pad index is kept, but the index might
138          point to a different lexical, because the PADLIST indices will be
139          different. See t/new_cv.t.
140
141          Warning: "$cv-"NEW_with_start> is disabled on some strict platforms,
142          like MSWin32.  See CPAN RT#28912.
143
144       $b_op->targ ( [ targ] )
145          Get or set the PADOFFSET.
146
147   EXPORT
148       None.
149

AUTHOR

151       Simon Cozens, "simon@cpan.org" Reini Urban, "rurban@cpan.org"
152

MAINTAINERS

154       Maintained by Reini Urban.
155
156       This is just a list of people who have submitted patches to the module:
157
158       Josh Jore, Michael Schwern, Jim Cromie, Scott Walters, Reini Urban,
159       Anton Berezin, Dmitry Karasik.
160
161       Maintainership permissions do have: Artur Bergman, Chia-liang Kao,
162       Anton Berezin, Jim Cromie, Joshua ben Jore, Michael G Schwern, Matt S
163       Trout, Reini Urban, Scott Walters.
164

LICENSE

166       This module is available under the same licences as perl, the Artistic
167       license and the GPL.
168