B::Concise(3) Perl Programmers Reference Guide B::Concise(3)NAMEB::Concise - Walk Perl syntax tree, printing concise info
about ops
SYNOPSIS
perl -MO=Concise[,OPTIONS] foo.pl
DESCRIPTION
This compiler backend prints the internal OPs of a Perl
program's syntax tree in one of several space-efficient
text formats suitable for debugging the inner workings of
perl or other compiler backends. It can print OPs in the
order they appear in the OP tree, in the order they will
execute, or in a text approximation to their tree struc
ture, and the format of the information displyed is cus
tomizable. Its function is similar to that of perl's -Dx
debugging flag or the B::Terse module, but it is more
sophisticated and flexible.
OPTIONS
Arguments that don't start with a hyphen are taken to be
the names of subroutines to print the OPs of; if no such
functions are specified, the main body of the program
(outside any subroutines, and not including use'd or
require'd files) is printed.
-basic
Print OPs in the order they appear in the OP tree (a
preorder traversal, starting at the root). The inden
tation of each OP shows its level in the tree. This
mode is the default, so the flag is included simply
for completeness.
-exec
Print OPs in the order they would normally execute
(for the majority of constructs this is a postorder
traversal of the tree, ending at the root). In most
cases the OP that usually follows a given OP will
appear directly below it; alternate paths are shown by
indentation. In cases like loops when control jumps
out of a linear path, a 'goto' line is generated.
-tree
Print OPs in a text approximation of a tree, with the
root of the tree at the left and 'left-to-right' order
of children transformed into 'top-to-bottom'. Because
this mode grows both to the right and down, it isn't
suitable for large programs (unless you have a very
wide terminal).
-compact
Use a tree format in which the minimum amount of space
is used for the lines connecting nodes (one character
in most cases). This squeezes out a few precious
columns of screen real estate.
-loose
Use a tree format that uses longer edges to separate
OP nodes. This format tends to look better than the
compact one, especially in ASCII, and is the default.
-vt Use tree connecting characters drawn from the VT100
line-drawing set. This looks better if your terminal
supports it.
-ascii
Draw the tree with standard ASCII characters like "+"
and "|". These don't look as clean as the VT100 char
acters, but they'll work with almost any terminal (or
the horizontal scrolling mode of less(1)) and are
suitable for text documentation or email. This is the
default.
-main
Include the main program in the output, even if sub
routines were also specified.
-basen
Print OP sequence numbers in base n. If n is greater
than 10, the digit for 11 will be 'a', and so on. If n
is greater than 36, the digit for 37 will be 'A', and
so on until 62. Values greater than 62 are not cur
rently supported. The default is 36.
-bigendian
Print sequence numbers with the most significant digit
first. This is the usual convention for Arabic numer
als, and the default.
-littleendian
Print seqence numbers with the least significant digit
first.
-concise
Use the author's favorite set of formatting conven
tions. This is the default, of course.
-terse
Use formatting conventions that emulate the ouput of
B::Terse. The basic mode is almost indistinguishable
from the real B::Terse, and the exec mode looks very
similar, but is in a more logical order and lacks
curly brackets. B::Terse doesn't have a tree mode, so
the tree mode is only vaguely reminiscient of
B::Terse.
-linenoise
Use formatting conventions in which the name of each
OP, rather than being written out in full, is repre
sented by a one- or two-character abbreviation. This
is mainly a joke.
-debug
Use formatting conventions reminiscient of B::Debug;
these aren't very concise at all.
-env
Use formatting conventions read from the environment
variables "B_CONCISE_FORMAT", "B_CONCISE_GOTO_FORMAT",
and "B_CONCISE_TREE_FORMAT".
FORMATTING SPECIFICATIONS
For each general style ('concise', 'terse', 'linenoise',
etc.) there are three specifications: one of how OPs
should appear in the basic or exec modes, one of how
'goto' lines should appear (these occur in the exec mode
only), and one of how nodes should appear in tree mode.
Each has the same format, described below. Any text that
doesn't match a special pattern is copied verbatim.
(x(exec_text;basic_text)x)
Generates exec_text in exec mode, or basic_text in
basic mode.
(*(text)*)
Generates one copy of text for each indentation level.
(*(text1;text2)*)
Generates one fewer copies of text1 than the indenta
tion level, followed by one copy of text2 if the
indentation level is more than 0.
(?(text1#varText2)?)
If the value of var is true (not empty or zero), gen
erates the value of var surrounded by text1 and Text2,
otherwise nothing.
#var
Generates the value of the variable var.
#varN
Generates the value of var, left jutified to fill N
spaces.
~ Any number of tildes and surrounding whitespace will
be collapsed to a single space.
The following variables are recognized:
#addr
The address of the OP, in hexidecimal.
#arg
The OP-specific information of the OP (such as the SV
for an SVOP, the non-local exit pointers for a LOOP,
etc.) enclosed in paretheses.
#class
The B-determined class of the OP, in all caps.
#classym
A single symbol abbreviating the class of the OP.
#coplabel
The label of the statement or block the OP is the
start of, if any.
#exname
The name of the OP, or 'ex-foo' if the OP is a null
that used to be a foo.
#extarg
The target of the OP, or nothing for a nulled OP.
#firstaddr
The address of the OP's first child, in hexidecimal.
#flags
The OP's flags, abbreviated as a series of symbols.
#flagval
The numeric value of the OP's flags.
#hyphenseq
The sequence number of the OP, or a hyphen if it
doesn't have one.
#label
'NEXT', 'LAST', or 'REDO' if the OP is a target of one
of those in exec mode, or empty otherwise.
#lastaddr
The address of the OP's last child, in hexidecimal.
#name
The OP's name.
#NAME
The OP's name, in all caps.
#next
The sequence number of the OP's next OP.
#nextaddr
The address of the OP's next OP, in hexidecimal.
#noise
The two-character abbreviation for the OP's name.
#private
The OP's private flags, rendered with abbreviated
names if possible.
#privval
The numeric value of the OP's private flags.
#seq
The sequence number of the OP.
#seqnum
The real sequence number of the OP, as a regular num
ber and not adjusted to be relative to the start of
the real program. (This will generally be a fairly
large number because all of B::Concise is compiled
before your program is).
#sibaddr
The address of the OP's next youngest sibling, in hex
idecimal.
#svaddr
The address of the OP's SV, if it has an SV, in hex
idecimal.
#svclass
The class of the OP's SV, if it has one, in all caps
(e.g., 'IV').
#svval
The value of the OP's SV, if it has one, in a short
human-readable format.
#targ
The numeric value of the OP's targ.
#targarg
The name of the variable the OP's targ refers to, if
any, otherwise the letter t followed by the OP's targ
in decimal.
#targarglife
Same as #targarg, but followed by the COP sequence
numbers that delimit the variable's lifetime (or 'end'
for a variable in an open scope) for a variable.
#typenum
The numeric value of the OP's type, in decimal.
ABBREVIATIONS
OP flags abbreviations
v OPf_WANT_VOID Want nothing (void context)
s OPf_WANT_SCALAR Want single value (scalar context)
l OPf_WANT_LIST Want list of any length (list context)
K OPf_KIDS There is a firstborn child.
P OPf_PARENS This operator was parenthesized.
(Or block needs explicit scope entry.)
R OPf_REF Certified reference.
(Return container, not containee).
M OPf_MOD Will modify (lvalue).
S OPf_STACKED Some arg is arriving on the stack.
* OPf_SPECIAL Do something weird for this op (see op.h)
OP class abbreviations
0 OP (aka BASEOP) An OP with no children
1 UNOP An OP with one child
2 BINOP An OP with two children
| LOGOP A control branch OP
@ LISTOP An OP that could have lots of children
/ PMOP An OP with a regular expression
$ SVOP An OP with an SV
" PVOP An OP with a string
{ LOOP An OP that holds pointers for a loop
; COP An OP that marks the start of a statement
AUTHOR
Stephen McCamant, "smcc@CSUA.Berkeley.EDU"
2001-02-22 perl v5.6.1 B::Concise(3)
