Add new dUNDERBAR and UNDERBAR macros, to help XS writers to

[p5sagit/p5-mst-13.2.git] / ext / B / B / Concise.pm

package B::Concise;
# Copyright (C) 2000-2003 Stephen McCamant. All rights reserved.
# This program is free software; you can redistribute and/or modify it
# under the same terms as Perl itself.

# Note: we need to keep track of how many use declarations/BEGIN
# blocks this module uses, so we can avoid printing them when user
# asks for the BEGIN blocks in her program. Update the comments and
# the count in concise_specials if you add or delete one. The
# -MO=Concise counts as use #1.

use strict; # use #2
use warnings; # uses #3 and #4, since warnings uses Carp

use Exporter (); # use #5

our $VERSION   = "0.61";
our @ISA       = qw(Exporter);
our @EXPORT_OK = qw(set_style set_style_standard add_callback
		    concise_subref concise_cv concise_main
		    add_style walk_output);

# use #6
use B qw(class ppname main_start main_root main_cv cstring svref_2object
	 SVf_IOK SVf_NOK SVf_POK SVf_IVisUV SVf_FAKE OPf_KIDS OPf_SPECIAL
	 CVf_ANON);

my %style =
  ("terse" =>
   ["(?(#label =>\n)?)(*(    )*)#class (#addr) #name (?([#targ])?) "
    . "#svclass~(?((#svaddr))?)~#svval~(?(label \"#coplabel\")?)\n",
    "(*(    )*)goto #class (#addr)\n",
    "#class pp_#name"],
   "concise" =>
   ["#hyphseq2 (*(   (x( ;)x))*)<#classsym> "
    . "#exname#arg(?([#targarglife])?)~#flags(?(/#private)?)(x(;~->#next)x)\n",
    "  (*(    )*)     goto #seq\n",
    "(?(<#seq>)?)#exname#arg(?([#targarglife])?)"],
   "linenoise" =>
   ["(x(;(*( )*))x)#noise#arg(?([#targarg])?)(x( ;\n)x)",
    "gt_#seq ",
    "(?(#seq)?)#noise#arg(?([#targarg])?)"],
   "debug" =>
   ["#class (#addr)\n\top_next\t\t#nextaddr\n\top_sibling\t#sibaddr\n\t"
    . "op_ppaddr\tPL_ppaddr[OP_#NAME]\n\top_type\t\t#typenum\n"
    . "\top_flags\t#flagval\n\top_private\t#privval\n"
    . "(?(\top_first\t#firstaddr\n)?)(?(\top_last\t\t#lastaddr\n)?)"
    . "(?(\top_sv\t\t#svaddr\n)?)",
    "    GOTO #addr\n",
    "#addr"],
   "env" => [$ENV{B_CONCISE_FORMAT}, $ENV{B_CONCISE_GOTO_FORMAT},
	     $ENV{B_CONCISE_TREE_FORMAT}],
  );

# Renderings, ie how Concise prints, is controlled by these vars
# primary:
our $stylename;		# selects current style from %style
my $order = "basic";	# how optree is walked & printed: basic, exec, tree

# rendering mechanics:
# these 'formats' are the line-rendering templates
# they're updated from %style when $stylename changes
my ($format, $gotofmt, $treefmt);

# lesser players:
my $base = 36;		# how <sequence#> is displayed
my $big_endian = 1;	# more <sequence#> display
my $tree_style = 0;	# tree-order details
my $banner = 1;		# print banner before optree is traversed

# another factor:
our @callbacks;		# allow external management

set_style_standard("concise");

my $curcv;
my $cop_seq_base;

sub set_style {
    ($format, $gotofmt, $treefmt) = @_;
    #warn "set_style: deprecated, use set_style_standard instead\n"; # someday
    die "expecting 3 style-format args\n" unless @_ == 3;
}

sub add_style {
    my ($newstyle,@args) = @_;
    die "style '$newstyle' already exists, choose a new name\n"
	if exists $style{$newstyle};
    die "expecting 3 style-format args\n" unless @args == 3;
    $style{$newstyle} = [@args];
    $stylename = $newstyle; # update rendering state
}

sub set_style_standard {
    ($stylename) = @_; # update rendering state
    die "err: style '$stylename' unknown\n" unless exists $style{$stylename};
    set_style(@{$style{$stylename}});
}

sub add_callback {
    push @callbacks, @_;
}

# output handle, used with all Concise-output printing
our $walkHandle = \*STDOUT;	# public for your convenience

sub walk_output { # updates $walkHandle
    my $handle = shift;
    if (ref $handle eq 'SCALAR') {
	require Config;
	die "no perlio in this build, can't call walk_output (\\\$scalar)\n"
	    unless $Config::Config{useperlio};
	# in 5.8+, open(FILEHANDLE,MODE,REFERENCE) writes to string
	open my $tmp, '>', $handle;	# but cant re-set existing STDOUT
	$walkHandle = $tmp;		# so use my $tmp as intermediate var
	return;
    }
    $walkHandle = $handle;
    my $iotype = ref $walkHandle;
    die "expecting argument/object that can print\n"
	unless $iotype eq 'GLOB' or $iotype and $walkHandle->can('print');
}

sub concise_subref {
    my($order, $coderef) = @_;
    my $codeobj = svref_2object($coderef);
    die "err: not a coderef: $coderef\n" unless ref $codeobj eq 'B::CV';#CODE';
    concise_cv_obj($order, $codeobj);
}

# This should have been called concise_subref, but it was exported
# under this name in versions before 0.56
sub concise_cv { concise_subref(@_); }

sub concise_cv_obj {
    my ($order, $cv) = @_;
    $curcv = $cv;
    die "err: coderef has no START\n" if class($cv->START) eq "NULL";
    sequence($cv->START);
    if ($order eq "exec") {
	walk_exec($cv->START);
    } elsif ($order eq "basic") {
	walk_topdown($cv->ROOT, sub { $_[0]->concise($_[1]) }, 0);
    } else {
	print $walkHandle tree($cv->ROOT, 0);
    }
}

sub concise_main {
    my($order) = @_;
    sequence(main_start);
    $curcv = main_cv;
    if ($order eq "exec") {
	return if class(main_start) eq "NULL";
	walk_exec(main_start);
    } elsif ($order eq "tree") {
	return if class(main_root) eq "NULL";
	print $walkHandle tree(main_root, 0);
    } elsif ($order eq "basic") {
	return if class(main_root) eq "NULL";
	walk_topdown(main_root,
		     sub { $_[0]->concise($_[1]) }, 0);
    }
}

sub concise_specials {
    my($name, $order, @cv_s) = @_;
    my $i = 1;
    if ($name eq "BEGIN") {
	splice(@cv_s, 0, 7); # skip 7 BEGIN blocks in this file
    } elsif ($name eq "CHECK") {
	pop @cv_s; # skip the CHECK block that calls us
    }
    for my $cv (@cv_s) {
	print $walkHandle "$name $i:\n";
	$i++;
	concise_cv_obj($order, $cv);
    }
}

my $start_sym = "\e(0"; # "\cN" sometimes also works
my $end_sym   = "\e(B"; # "\cO" respectively

my @tree_decorations =
  (["  ", "--", "+-", "|-", "| ", "`-", "-", 1],
   [" ", "-", "+", "+", "|", "`", "", 0],
   ["  ", map("$start_sym$_$end_sym", "qq", "wq", "tq", "x ", "mq", "q"), 1],
   [" ", map("$start_sym$_$end_sym", "q", "w", "t", "x", "m"), "", 0],
  );

sub compile {
    my @options = grep(/^-/, @_);
    my @args = grep(!/^-/, @_);
    my $do_main = 0;
    for my $o (@options) {
	if ($o eq "-basic") {
	    $order = "basic";
	} elsif ($o eq "-exec") {
	    $order = "exec";
	} elsif ($o eq "-tree") {
	    $order = "tree";
	} elsif ($o eq "-compact") {
	    $tree_style |= 1;
	} elsif ($o eq "-loose") {
	    $tree_style &= ~1;
	} elsif ($o eq "-vt") {
	    $tree_style |= 2;
	} elsif ($o eq "-ascii") {
	    $tree_style &= ~2;
	} elsif ($o eq "-main") {
	    $do_main = 1;
	} elsif ($o =~ /^-base(\d+)$/) {
	    $base = $1;
	} elsif ($o eq "-bigendian") {
	    $big_endian = 1;
	} elsif ($o eq "-littleendian") {
	    $big_endian = 0;
	} elsif ($o eq "-banner") {
	    $banner = 0;
	}
	elsif (exists $style{substr($o, 1)}) {
	    $stylename = substr($o, 1);
	    set_style_standard($stylename);
	} else {
	    warn "Option $o unrecognized";
	}
    }
    return sub {
	if (@args) {
	    for my $objname (@args) {
		if ($objname eq "BEGIN") {
		    concise_specials("BEGIN", $order,
				     B::begin_av->isa("B::AV") ?
				     B::begin_av->ARRAY : ());
		} elsif ($objname eq "INIT") {
		    concise_specials("INIT", $order,
				     B::init_av->isa("B::AV") ?
				     B::init_av->ARRAY : ());
		} elsif ($objname eq "CHECK") {
		    concise_specials("CHECK", $order,
				     B::check_av->isa("B::AV") ?
				     B::check_av->ARRAY : ());
		} elsif ($objname eq "END") {
		    concise_specials("END", $order,
				     B::end_av->isa("B::AV") ?
				     B::end_av->ARRAY : ());
		} else {
		    # convert function names to subrefs
		    my $objref;
		    if (ref $objname) {
			print $walkHandle "B::Concise::compile($objname)\n"
			    if $banner;
			$objref = $objname;
		    } else {
			$objname = "main::" . $objname unless $objname =~ /::/;
			print $walkHandle "$objname:\n";
			no strict 'refs';
			die "err: unknown function ($objname)\n"
			    unless *{$objname}{CODE};
			$objref = \&$objname;
		    }
		    concise_subref($order, $objref);
		}
	    }
	}
	if (!@args or $do_main) {
	    print $walkHandle "main program:\n" if $do_main;
	    concise_main($order);
	}
    }
}

my %labels;
my $lastnext;	# remembers op-chain, used to insert gotos

my %opclass = ('OP' => "0", 'UNOP' => "1", 'BINOP' => "2", 'LOGOP' => "|",
	       'LISTOP' => "@", 'PMOP' => "/", 'SVOP' => "\$", 'GVOP' => "*",
	       'PVOP' => '"', 'LOOP' => "{", 'COP' => ";", 'PADOP' => "#");

no warnings 'qw'; # "Possible attempt to put comments..."; use #7
my @linenoise =
  qw'#  () sc (  @? 1  $* gv *{ m$ m@ m% m? p/ *$ $  $# & a& pt \\ s\\ rf bl
     `  *? <> ?? ?/ r/ c/ // qr s/ /c y/ =  @= C  sC Cp sp df un BM po +1 +I
     -1 -I 1+ I+ 1- I- ** *  i* /  i/ %$ i% x  +  i+ -  i- .  "  << >> <  i<
     >  i> <= i, >= i. == i= != i! <? i? s< s> s, s. s= s! s? b& b^ b| -0 -i
     !  ~  a2 si cs rd sr e^ lg sq in %x %o ab le ss ve ix ri sf FL od ch cy
     uf lf uc lc qm @  [f [  @[ eh vl ky dl ex %  ${ @{ uk pk st jn )  )[ a@
     a% sl +] -] [- [+ so rv GS GW MS MW .. f. .f && || ^^ ?: &= |= -> s{ s}
     v} ca wa di rs ;; ;  ;d }{ {  }  {} f{ it {l l} rt }l }n }r dm }g }e ^o
     ^c ^| ^# um bm t~ u~ ~d DB db ^s se ^g ^r {w }w pf pr ^O ^K ^R ^W ^d ^v
     ^e ^t ^k t. fc ic fl .s .p .b .c .l .a .h g1 s1 g2 s2 ?. l? -R -W -X -r
     -w -x -e -o -O -z -s -M -A -C -S -c -b -f -d -p -l -u -g -k -t -T -B cd
     co cr u. cm ut r. l@ s@ r@ mD uD oD rD tD sD wD cD f$ w$ p$ sh e$ k$ g3
     g4 s4 g5 s5 T@ C@ L@ G@ A@ S@ Hg Hc Hr Hw Mg Mc Ms Mr Sg Sc So rq do {e
     e} {t t} g6 G6 6e g7 G7 7e g8 G8 8e g9 G9 9e 6s 7s 8s 9s 6E 7E 8E 9E Pn
     Pu GP SP EP Gn Gg GG SG EG g0 c$ lk t$ ;s n> // /= CO';

my $chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

sub op_flags {
    my($x) = @_;
    my(@v);
    push @v, "v" if ($x & 3) == 1;
    push @v, "s" if ($x & 3) == 2;
    push @v, "l" if ($x & 3) == 3;
    push @v, "K" if $x & 4;
    push @v, "P" if $x & 8;
    push @v, "R" if $x & 16;
    push @v, "M" if $x & 32;
    push @v, "S" if $x & 64;
    push @v, "*" if $x & 128;
    return join("", @v);
}

sub base_n {
    my $x = shift;
    return "-" . base_n(-$x) if $x < 0;
    my $str = "";
    do { $str .= substr($chars, $x % $base, 1) } while $x = int($x / $base);
    $str = reverse $str if $big_endian;
    return $str;
}

my %sequence_num;
my $seq_max = 1;

sub reset_sequence {
    # reset the sequence
    %sequence_num = ();
    $seq_max = 1;
}

sub seq {
    my($op) = @_;
    return "-" if not exists $sequence_num{$$op};
    return base_n($sequence_num{$$op});
}

sub walk_topdown {
    my($op, $sub, $level) = @_;
    $sub->($op, $level);
    if ($op->flags & OPf_KIDS) {
	for (my $kid = $op->first; $$kid; $kid = $kid->sibling) {
	    walk_topdown($kid, $sub, $level + 1);
	}
    }
    if (class($op) eq "PMOP") {
	my $maybe_root = $op->pmreplroot;
	if (ref($maybe_root) and $maybe_root->isa("B::OP")) {
	    # It really is the root of the replacement, not something
	    # else stored here for lack of space elsewhere
	    walk_topdown($maybe_root, $sub, $level + 1);
	}
    }
}

sub walklines {
    my($ar, $level) = @_;
    for my $l (@$ar) {
	if (ref($l) eq "ARRAY") {
	    walklines($l, $level + 1);
	} else {
	    $l->concise($level);
	}
    }
}

sub walk_exec {
    my($top, $level) = @_;
    my %opsseen;
    my @lines;
    my @todo = ([$top, \@lines]);
    while (@todo and my($op, $targ) = @{shift @todo}) {
	for (; $$op; $op = $op->next) {
	    last if $opsseen{$$op}++;
	    push @$targ, $op;
	    my $name = $op->name;
	    if (class($op) eq "LOGOP") {
		my $ar = [];
		push @$targ, $ar;
		push @todo, [$op->other, $ar];
	    } elsif ($name eq "subst" and $ {$op->pmreplstart}) {
		my $ar = [];
		push @$targ, $ar;
		push @todo, [$op->pmreplstart, $ar];
	    } elsif ($name =~ /^enter(loop|iter)$/) {
		$labels{${$op->nextop}} = "NEXT";
		$labels{${$op->lastop}} = "LAST";
		$labels{${$op->redoop}} = "REDO";
	    }
	}
    }
    walklines(\@lines, 0);
}

# The structure of this routine is purposely modeled after op.c's peep()
sub sequence {
    my($op) = @_;
    my $oldop = 0;
    return if class($op) eq "NULL" or exists $sequence_num{$$op};
    for (; $$op; $op = $op->next) {
	last if exists $sequence_num{$$op};
	my $name = $op->name;
	if ($name =~ /^(null|scalar|lineseq|scope)$/) {
	    next if $oldop and $ {$op->next};
	} else {
	    $sequence_num{$$op} = $seq_max++;
	    if (class($op) eq "LOGOP") {
		my $other = $op->other;
		$other = $other->next while $other->name eq "null";
		sequence($other);
	    } elsif (class($op) eq "LOOP") {
		my $redoop = $op->redoop;
		$redoop = $redoop->next while $redoop->name eq "null";
		sequence($redoop);
		my $nextop = $op->nextop;
		$nextop = $nextop->next while $nextop->name eq "null";
		sequence($nextop);
		my $lastop = $op->lastop;
		$lastop = $lastop->next while $lastop->name eq "null";
		sequence($lastop);
	    } elsif ($name eq "subst" and $ {$op->pmreplstart}) {
		my $replstart = $op->pmreplstart;
		$replstart = $replstart->next while $replstart->name eq "null";
		sequence($replstart);
	    }
	}
	$oldop = $op;
    }
}

sub fmt_line {    # generate text-line for op.
    my($hr, $text, $level) = @_;
    return '' if $hr->{SKIP};	# suppress line if a callback said so

    $text =~ s/\(\?\(([^\#]*?)\#(\w+)([^\#]*?)\)\?\)/
	$hr->{$2} ? $1.$hr->{$2}.$3 : ""/eg;

    $text =~ s/\(x\((.*?);(.*?)\)x\)/$order eq "exec" ? $1 : $2/egs;
    $text =~ s/\(\*\(([^;]*?)\)\*\)/$1 x $level/egs;
    $text =~ s/\(\*\((.*?);(.*?)\)\*\)/$1 x ($level - 1) . $2 x ($level>0)/egs;
    $text =~ s/\#([a-zA-Z]+)(\d+)/sprintf("%-$2s", $hr->{$1})/eg;

    $text =~ s/\#([a-zA-Z]+)/$hr->{$1}/eg;  # populate data into template
    $text =~ s/[ \t]*~+[ \t]*/ /g;
    chomp $text;
    return "$text\n" if $text ne "";
    return $text; # suppress empty lines
}

my %priv;
$priv{$_}{128} = "LVINTRO"
  for ("pos", "substr", "vec", "threadsv", "gvsv", "rv2sv", "rv2hv", "rv2gv",
       "rv2av", "rv2arylen", "aelem", "helem", "aslice", "hslice", "padsv",
       "padav", "padhv", "enteriter");
$priv{$_}{64} = "REFC" for ("leave", "leavesub", "leavesublv", "leavewrite");
$priv{"aassign"}{64} = "COMMON";
$priv{"aassign"}{32} = "PHASH" if $] < 5.009;
$priv{"sassign"}{64} = "BKWARD";
$priv{$_}{64} = "RTIME" for ("match", "subst", "substcont");
@{$priv{"trans"}}{1,2,4,8,16,64} = ("<UTF", ">UTF", "IDENT", "SQUASH", "DEL",
				    "COMPL", "GROWS");
$priv{"repeat"}{64} = "DOLIST";
$priv{"leaveloop"}{64} = "CONT";
@{$priv{$_}}{32,64,96} = ("DREFAV", "DREFHV", "DREFSV")
  for (qw(rv2gv rv2sv padsv aelem helem));
$priv{"entersub"}{16} = "DBG";
$priv{"entersub"}{32} = "TARG";
@{$priv{$_}}{4,8,128} = ("INARGS","AMPER","NO()") for ("entersub", "rv2cv");
$priv{"gv"}{32} = "EARLYCV";
$priv{"aelem"}{16} = $priv{"helem"}{16} = "LVDEFER";
$priv{$_}{16} = "OURINTR" for ("gvsv", "rv2sv", "rv2av", "rv2hv", "r2gv",
	"enteriter");
$priv{$_}{16} = "TARGMY"
  for (map(($_,"s$_"),"chop", "chomp"),
       map(($_,"i_$_"), "postinc", "postdec", "multiply", "divide", "modulo",
	   "add", "subtract", "negate"), "pow", "concat", "stringify",
       "left_shift", "right_shift", "bit_and", "bit_xor", "bit_or",
       "complement", "atan2", "sin", "cos", "rand", "exp", "log", "sqrt",
       "int", "hex", "oct", "abs", "length", "index", "rindex", "sprintf",
       "ord", "chr", "crypt", "quotemeta", "join", "push", "unshift", "flock",
       "chdir", "chown", "chroot", "unlink", "chmod", "utime", "rename",
       "link", "symlink", "mkdir", "rmdir", "wait", "waitpid", "system",
       "exec", "kill", "getppid", "getpgrp", "setpgrp", "getpriority",
       "setpriority", "time", "sleep");
@{$priv{"const"}}{8,16,32,64,128} = ("STRICT","ENTERED", '$[', "BARE", "WARN");
$priv{"flip"}{64} = $priv{"flop"}{64} = "LINENUM";
$priv{"list"}{64} = "GUESSED";
$priv{"delete"}{64} = "SLICE";
$priv{"exists"}{64} = "SUB";
$priv{$_}{64} = "LOCALE"
  for ("sort", "prtf", "sprintf", "slt", "sle", "seq", "sne", "sgt", "sge",
       "scmp", "lc", "uc", "lcfirst", "ucfirst");
@{$priv{"sort"}}{1,2,4,8} = ("NUM", "INT", "REV", "INPLACE");
$priv{"threadsv"}{64} = "SVREFd";
@{$priv{$_}}{16,32,64,128} = ("INBIN","INCR","OUTBIN","OUTCR")
  for ("open", "backtick");
$priv{"exit"}{128} = "VMS";
$priv{$_}{2} = "FTACCESS"
  for ("ftrread", "ftrwrite", "ftrexec", "fteread", "ftewrite", "fteexec");
if ($] >= 5.009) {
  # Stacked filetests are post 5.8.x
  $priv{$_}{4} = "FTSTACKED"
    for ("ftrread", "ftrwrite", "ftrexec", "fteread", "ftewrite", "fteexec",
         "ftis", "fteowned", "ftrowned", "ftzero", "ftsize", "ftmtime",
	 "ftatime", "ftctime", "ftsock", "ftchr", "ftblk", "ftfile", "ftdir",
	 "ftpipe", "ftlink", "ftsuid", "ftsgid", "ftsvtx", "fttty", "fttext",
	 "ftbinary");
  # Lexical $_ is post 5.8.x
  $priv{$_}{2} = "GREPLEX"
    for ("mapwhile", "mapstart", "grepwhile", "grepstart");
}

sub private_flags {
    my($name, $x) = @_;
    my @s;
    for my $flag (128, 96, 64, 32, 16, 8, 4, 2, 1) {
	if ($priv{$name}{$flag} and $x & $flag and $x >= $flag) {
	    $x -= $flag;
	    push @s, $priv{$name}{$flag};
	}
    }
    push @s, $x if $x;
    return join(",", @s);
}

sub concise_sv {
    my($sv, $hr) = @_;
    $hr->{svclass} = class($sv);
    $hr->{svclass} = "UV"
      if $hr->{svclass} eq "IV" and $sv->FLAGS & SVf_IVisUV;
    $hr->{svaddr} = sprintf("%#x", $$sv);
    if ($hr->{svclass} eq "GV") {
	my $gv = $sv;
	my $stash = $gv->STASH->NAME;
	if ($stash eq "main") {
	    $stash = "";
	} else {
	    $stash = $stash . "::";
	}
	$hr->{svval} = "*$stash" . $gv->SAFENAME;
	return "*$stash" . $gv->SAFENAME;
    } else {
	while (class($sv) eq "RV") {
	    $hr->{svval} .= "\\";
	    $sv = $sv->RV;
	}
	if (class($sv) eq "SPECIAL") {
	    $hr->{svval} .= ["Null", "sv_undef", "sv_yes", "sv_no"]->[$$sv];
	} elsif ($sv->FLAGS & SVf_NOK) {
	    $hr->{svval} .= $sv->NV;
	} elsif ($sv->FLAGS & SVf_IOK) {
	    $hr->{svval} .= $sv->int_value;
	} elsif ($sv->FLAGS & SVf_POK) {
	    $hr->{svval} .= cstring($sv->PV);
	} elsif (class($sv) eq "HV") {
	    $hr->{svval} .= 'HASH';
	}
	return $hr->{svclass} . " " .  $hr->{svval};
    }
}

sub concise_op {
    my ($op, $level, $format) = @_;
    my %h;
    $h{exname} = $h{name} = $op->name;
    $h{NAME} = uc $h{name};
    $h{class} = class($op);
    $h{extarg} = $h{targ} = $op->targ;
    $h{extarg} = "" unless $h{extarg};
    if ($h{name} eq "null" and $h{targ}) {
	# targ holds the old type
	$h{exname} = "ex-" . substr(ppname($h{targ}), 3);
	$h{extarg} = "";
    } elsif ($op->name =~ /^leave(sub(lv)?|write)?$/) {
	# targ potentially holds a reference count
	if ($op->private & 64) {
	    my $refs = "ref" . ($h{targ} != 1 ? "s" : "");
	    $h{targarglife} = $h{targarg} = "$h{targ} $refs";
	}
    } elsif ($h{targ}) {
	my $padname = (($curcv->PADLIST->ARRAY)[0]->ARRAY)[$h{targ}];
	if (defined $padname and class($padname) ne "SPECIAL") {
	    $h{targarg}  = $padname->PVX;
	    if ($padname->FLAGS & SVf_FAKE) {
		if ($] < 5.009) {
		    $h{targarglife} = "$h{targarg}:FAKE";
		} else {
		    # These changes relate to the jumbo closure fix.
		    # See changes 19939 and 20005
		    my $fake = '';
		    $fake .= 'a' if $padname->IVX & 1; # PAD_FAKELEX_ANON
		    $fake .= 'm' if $padname->IVX & 2; # PAD_FAKELEX_MULTI
		    $fake .= ':' . $padname->NVX if $curcv->CvFLAGS & CVf_ANON;
		    $h{targarglife} = "$h{targarg}:FAKE:$fake";
		}
	    }
	    else {
		my $intro = $padname->NVX - $cop_seq_base;
		my $finish = int($padname->IVX) - $cop_seq_base;
		$finish = "end" if $finish == 999999999 - $cop_seq_base;
		$h{targarglife} = "$h{targarg}:$intro,$finish";
	    }
	} else {
	    $h{targarglife} = $h{targarg} = "t" . $h{targ};
	}
    }
    $h{arg} = "";
    $h{svclass} = $h{svaddr} = $h{svval} = "";
    if ($h{class} eq "PMOP") {
	my $precomp = $op->precomp;
	if (defined $precomp) {
	    $precomp = cstring($precomp); # Escape literal control sequences
 	    $precomp = "/$precomp/";
	} else {
	    $precomp = "";
	}
	my $pmreplroot = $op->pmreplroot;
	my $pmreplstart;
	if (ref($pmreplroot) eq "B::GV") {
	    # with C<@stash_array = split(/pat/, str);>,
	    #  *stash_array is stored in /pat/'s pmreplroot.
	    $h{arg} = "($precomp => \@" . $pmreplroot->NAME . ")";
	} elsif (!ref($pmreplroot) and $pmreplroot) {
	    # same as the last case, except the value is actually a
	    # pad offset for where the GV is kept (this happens under
	    # ithreads)
	    my $gv = (($curcv->PADLIST->ARRAY)[1]->ARRAY)[$pmreplroot];
	    $h{arg} = "($precomp => \@" . $gv->NAME . ")";
	} elsif ($ {$op->pmreplstart}) {
	    undef $lastnext;
	    $pmreplstart = "replstart->" . seq($op->pmreplstart);
	    $h{arg} = "(" . join(" ", $precomp, $pmreplstart) . ")";
	} else {
	    $h{arg} = "($precomp)";
	}
    } elsif ($h{class} eq "PVOP" and $h{name} ne "trans") {
	$h{arg} = '("' . $op->pv . '")';
	$h{svval} = '"' . $op->pv . '"';
    } elsif ($h{class} eq "COP") {
	my $label = $op->label;
	$h{coplabel} = $label;
	$label = $label ? "$label: " : "";
	my $loc = $op->file;
	$loc =~ s[.*/][];
	$loc .= ":" . $op->line;
	my($stash, $cseq) = ($op->stash->NAME, $op->cop_seq - $cop_seq_base);
	my $arybase = $op->arybase;
	$arybase = $arybase ? ' $[=' . $arybase : "";
	$h{arg} = "($label$stash $cseq $loc$arybase)";
    } elsif ($h{class} eq "LOOP") {
	$h{arg} = "(next->" . seq($op->nextop) . " last->" . seq($op->lastop)
	  . " redo->" . seq($op->redoop) . ")";
    } elsif ($h{class} eq "LOGOP") {
	undef $lastnext;
	$h{arg} = "(other->" . seq($op->other) . ")";
    } elsif ($h{class} eq "SVOP") {
	unless ($h{name} eq 'aelemfast' and $op->flags & OPf_SPECIAL) {
	    if (! ${$op->sv}) {
		my $sv = (($curcv->PADLIST->ARRAY)[1]->ARRAY)[$op->targ];
		$h{arg} = "[" . concise_sv($sv, \%h) . "]";
		$h{targarglife} = $h{targarg} = "";
	    } else {
		$h{arg} = "(" . concise_sv($op->sv, \%h) . ")";
	    }
	}
    } elsif ($h{class} eq "PADOP") {
	my $sv = (($curcv->PADLIST->ARRAY)[1]->ARRAY)[$op->padix];
	$h{arg} = "[" . concise_sv($sv, \%h) . "]";
    }
    $h{seq} = $h{hyphseq} = seq($op);
    $h{seq} = "" if $h{seq} eq "-";
    $h{opt} = $op->opt;
    $h{static} = $op->static;
    $h{next} = $op->next;
    $h{next} = (class($h{next}) eq "NULL") ? "(end)" : seq($h{next});
    $h{nextaddr} = sprintf("%#x", $ {$op->next});
    $h{sibaddr} = sprintf("%#x", $ {$op->sibling});
    $h{firstaddr} = sprintf("%#x", $ {$op->first}) if $op->can("first");
    $h{lastaddr} = sprintf("%#x", $ {$op->last}) if $op->can("last");

    $h{classsym} = $opclass{$h{class}};
    $h{flagval} = $op->flags;
    $h{flags} = op_flags($op->flags);
    $h{privval} = $op->private;
    $h{private} = private_flags($h{name}, $op->private);
    $h{addr} = sprintf("%#x", $$op);
    $h{label} = $labels{$$op};
    $h{typenum} = $op->type;
    $h{noise} = $linenoise[$op->type];

    $_->(\%h, $op, \$format, \$level, $stylename) for @callbacks;
    return fmt_line(\%h, $format, $level);
}

sub B::OP::concise {
    my($op, $level) = @_;
    if ($order eq "exec" and $lastnext and $$lastnext != $$op) {
	# insert a 'goto' line
	my $h = {"seq" => seq($lastnext), "class" => class($lastnext),
		 "addr" => sprintf("%#x", $$lastnext)};
	print $walkHandle fmt_line($h, $gotofmt, $level+1);
    }
    $lastnext = $op->next;
    print $walkHandle concise_op($op, $level, $format);
}

# B::OP::terse (see Terse.pm) now just calls this
sub b_terse {
    my($op, $level) = @_;

    # This isn't necessarily right, but there's no easy way to get
    # from an OP to the right CV. This is a limitation of the
    # ->terse() interface style, and there isn't much to do about
    # it. In particular, we can die in concise_op if the main pad
    # isn't long enough, or has the wrong kind of entries, compared to
    # the pad a sub was compiled with. The fix for that would be to
    # make a backwards compatible "terse" format that never even
    # looked at the pad, just like the old B::Terse. I don't think
    # that's worth the effort, though.
    $curcv = main_cv unless $curcv;

    if ($order eq "exec" and $lastnext and $$lastnext != $$op) {
	# insert a 'goto'
	my $h = {"seq" => seq($lastnext), "class" => class($lastnext),
		 "addr" => sprintf("%#x", $$lastnext)};
	print fmt_line($h, $style{"terse"}[1], $level+1);
    }
    $lastnext = $op->next;
    print concise_op($op, $level, $style{"terse"}[0]);
}

sub tree {
    my $op = shift;
    my $level = shift;
    my $style = $tree_decorations[$tree_style];
    my($space, $single, $kids, $kid, $nokid, $last, $lead, $size) = @$style;
    my $name = concise_op($op, $level, $treefmt);
    if (not $op->flags & OPf_KIDS) {
	return $name . "\n";
    }
    my @lines;
    for (my $kid = $op->first; $$kid; $kid = $kid->sibling) {
	push @lines, tree($kid, $level+1);
    }
    my $i;
    for ($i = $#lines; substr($lines[$i], 0, 1) eq " "; $i--) {
	$lines[$i] = $space . $lines[$i];
    }
    if ($i > 0) {
	$lines[$i] = $last . $lines[$i];
	while ($i-- > 1) {
	    if (substr($lines[$i], 0, 1) eq " ") {
		$lines[$i] = $nokid . $lines[$i];
	    } else {
		$lines[$i] = $kid . $lines[$i];
	    }
	}
	$lines[$i] = $kids . $lines[$i];
    } else {
	$lines[0] = $single . $lines[0];
    }
    return("$name$lead" . shift @lines,
           map(" " x (length($name)+$size) . $_, @lines));
}

# *** Warning: fragile kludge ahead ***
# Because the B::* modules run in the same interpreter as the code
# they're compiling, their presence tends to distort the view we have of
# the code we're looking at. In particular, perl gives sequence numbers
# to COPs. If the program we're looking at were run on its own, this
# would start at 1. Because all of B::Concise and all the modules it
# uses are compiled first, though, by the time we get to the user's
# program the sequence number is already pretty high, which could be
# distracting if you're trying to tell OPs apart. Therefore we'd like to
# subtract an offset from all the sequence numbers we display, to
# restore the simpler view of the world. The trick is to know what that
# offset will be, when we're still compiling B::Concise!  If we
# hardcoded a value, it would have to change every time B::Concise or
# other modules we use do. To help a little, what we do here is compile
# a little code at the end of the module, and compute the base sequence
# number for the user's program as being a small offset later, so all we
# have to worry about are changes in the offset.
 
# When you say "perl -MO=Concise -e '$a'", the output should look like:

# 4  <@> leave[t1] vKP/REFC ->(end)
# 1     <0> enter ->2
 #^ smallest OP sequence number should be 1
# 2     <;> nextstate(main 1 -e:1) v ->3
 #                         ^ smallest COP sequence number should be 1
# -     <1> ex-rv2sv vK/1 ->4
# 3        <$> gvsv(*a) s ->4

# If the second of the marked numbers there isn't 1, it means you need
# to update the corresponding magic number in the next line.
# Remember, this needs to stay the last things in the module.

# Why is this different for MacOS?  Does it matter?
my $cop_seq_mnum = $^O eq 'MacOS' ? 12 : 11;
$cop_seq_base = svref_2object(eval 'sub{0;}')->START->cop_seq + $cop_seq_mnum;

1;

__END__

=head1 NAME

B::Concise - Walk Perl syntax tree, printing concise info about ops

=head1 SYNOPSIS

    perl -MO=Concise[,OPTIONS] foo.pl

    use B::Concise qw(set_style add_callback);

=head1 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 structure, and the format of the
information displyed is customizable. Its function is similar to that of
perl's B<-Dx> debugging flag or the B<B::Terse> module, but it is more
sophisticated and flexible.

=head1 EXAMPLE

Here's is a short example of output (aka 'rendering'), using the
default formatting conventions :

    % perl -MO=Concise -e '$a = $b + 42'
    8  <@> leave[1 ref] vKP/REFC ->(end)
    1     <0> enter ->2
    2     <;> nextstate(main 1 -e:1) v ->3
    7     <2> sassign vKS/2 ->8
    5        <2> add[t1] sK/2 ->6
    -           <1> ex-rv2sv sK/1 ->4
    3              <$> gvsv(*b) s ->4
    4           <$> const(IV 42) s ->5
    -        <1> ex-rv2sv sKRM*/1 ->7
    6           <$> gvsv(*a) s ->7

Each line corresponds to an opcode. Null ops appear as C<ex-opname>,
where I<opname> is the op that has been optimized away by perl.

The number on the first row indicates the op's sequence number. It's
given in base 36 by default.

The symbol between angle brackets indicates the op's type : for example,
<2> is a BINOP, <@> a LISTOP, etc. (see L</"OP class abbreviations">).

The opname may be followed by op-specific information in parentheses
(e.g. C<gvsv(*b)>), and by targ information in brackets (e.g.
C<leave[t1]>).

Next come the op flags. The common flags are listed below
(L</"OP flags abbreviations">). The private flags follow, separated
by a slash. For example, C<vKP/REFC> means that the leave op has
public flags OPf_WANT_VOID, OPf_KIDS, and OPf_PARENS, and the private
flag OPpREFCOUNTED.

Finally an arrow points to the sequence number of the next op.

=head1 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. Passing C<BEGIN>,
C<CHECK>, C<INIT>, or C<END> will cause all of the corresponding
special blocks to be printed.

Options affect how things are rendered (ie printed).  They're presented
here by their visual effect, 1st being strongest.  They're grouped
according to how they interrelate; within each group the options are
mutually exclusive (unless otherwise stated).

=head2 Options for Opcode Ordering

These options control the 'vertical display' of opcodes.  The display
'order' is also called 'mode' elsewhere in this document.

=over 4

=item B<-basic>

Print OPs in the order they appear in the OP tree (a preorder
traversal, starting at the root). The indentation of each OP shows its
level in the tree.  This mode is the default, so the flag is included
simply for completeness.

=item B<-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.

=item B<-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).

=back

=head2 Options for Line-Style

These options select the line-style (or just style) used to render
each opcode, and dictates what info is actually printed into each line.

=over 4

=item B<-concise>

Use the author's favorite set of formatting conventions. This is the
default, of course.

=item B<-terse>

Use formatting conventions that emulate the output of B<B::Terse>. The
basic mode is almost indistinguishable from the real B<B::Terse>, and the
exec mode looks very similar, but is in a more logical order and lacks
curly brackets. B<B::Terse> doesn't have a tree mode, so the tree mode
is only vaguely reminiscent of B<B::Terse>.

=item B<-linenoise>

Use formatting conventions in which the name of each OP, rather than being
written out in full, is represented by a one- or two-character abbreviation.
This is mainly a joke.

=item B<-debug>

Use formatting conventions reminiscent of B<B::Debug>; these aren't
very concise at all.

=item B<-env>

Use formatting conventions read from the environment variables
C<B_CONCISE_FORMAT>, C<B_CONCISE_GOTO_FORMAT>, and C<B_CONCISE_TREE_FORMAT>.

=back

=head2 Options for tree-specific formatting

=over 4

=item B<-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.

=item B<-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.

=item B<-vt>

Use tree connecting characters drawn from the VT100 line-drawing set.
This looks better if your terminal supports it.

=item B<-ascii>

Draw the tree with standard ASCII characters like C<+> and C<|>. These don't
look as clean as the VT100 characters, 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.

=back

These are pairwise exclusive, i.e. compact or loose, vt or ascii.

=head2 Options controlling sequence numbering

=over 4

=item B<-base>I<n>

Print OP sequence numbers in base I<n>. If I<n> is greater than 10, the
digit for 11 will be 'a', and so on. If I<n> is greater than 36, the digit
for 37 will be 'A', and so on until 62. Values greater than 62 are not
currently supported. The default is 36.

=item B<-bigendian>

Print sequence numbers with the most significant digit first. This is the
usual convention for Arabic numerals, and the default.

=item B<-littleendian>

Print seqence numbers with the least significant digit first.  This is
obviously mutually exclusive with bigendian.

=back

=head2 Other options

=over 4

=item B<-main>

Include the main program in the output, even if subroutines were also
specified.  This is the only option that is not sticky (see below)

=item B<-banner>

B::Concise::compile normally prints a banner line identifying the
function name, or in case of a subref, a generic message including
(unfortunately) the stringified coderef.  This option suppresses the
printing of the banner.

=back

=head2 Option Stickiness

If you invoke Concise more than once in a program, you should know that
the options are 'sticky'.  This means that the options you provide in
the first call will be remembered for the 2nd call, unless you
re-specify or change them.

=head1 FORMATTING SPECIFICATIONS

For each line-style ('concise', 'terse', 'linenoise', etc.) there are
3 format-specs which control how OPs are rendered.

The first is the 'default' format, which is used in both basic and exec
modes to print all opcodes.  The 2nd, goto-format, is used in exec
mode when branches are encountered.  They're not real opcodes, and are
inserted to look like a closing curly brace.  The tree-format is tree
specific.

When a line is rendered, the correct format string is scanned for the
following items, and data is substituted in, or other manipulations,
like basic indenting.  Any text that doesn't match a special pattern
(the items below) is copied verbatim.  (Yes, it's a set of s///g steps.)

=over 4

=item B<(x(>I<exec_text>B<;>I<basic_text>B<)x)>

Generates I<exec_text> in exec mode, or I<basic_text> in basic mode.

=item B<(*(>I<text>B<)*)>

Generates one copy of I<text> for each indentation level.

=item B<(*(>I<text1>B<;>I<text2>B<)*)>

Generates one fewer copies of I<text1> than the indentation level, followed
by one copy of I<text2> if the indentation level is more than 0.

=item B<(?(>I<text1>B<#>I<var>I<Text2>B<)?)>

If the value of I<var> is true (not empty or zero), generates the
value of I<var> surrounded by I<text1> and I<Text2>, otherwise
nothing.

=item B<#>I<var>

Generates the value of the variable I<var>.

=item B<#>I<var>I<N>

Generates the value of I<var>, left jutified to fill I<N> spaces.

=item B<~>

Any number of tildes and surrounding whitespace will be collapsed to
a single space.

=back

The following variables are recognized:

=over 4

=item B<#addr>

The address of the OP, in hexidecimal.

=item B<#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.

=item B<#class>

The B-determined class of the OP, in all caps.

=item B<#classsym>

A single symbol abbreviating the class of the OP.

=item B<#coplabel>

The label of the statement or block the OP is the start of, if any.

=item B<#exname>

The name of the OP, or 'ex-foo' if the OP is a null that used to be a foo.

=item B<#extarg>

The target of the OP, or nothing for a nulled OP.

=item B<#firstaddr>

The address of the OP's first child, in hexidecimal.

=item B<#flags>

The OP's flags, abbreviated as a series of symbols.

=item B<#flagval>

The numeric value of the OP's flags.

=item B<#hyphseq>

The sequence number of the OP, or a hyphen if it doesn't have one.

=item B<#label>

'NEXT', 'LAST', or 'REDO' if the OP is a target of one of those in exec
mode, or empty otherwise.

=item B<#lastaddr>

The address of the OP's last child, in hexidecimal.

=item B<#name>

The OP's name.

=item B<#NAME>

The OP's name, in all caps.

=item B<#next>

The sequence number of the OP's next OP.

=item B<#nextaddr>

The address of the OP's next OP, in hexidecimal.

=item B<#noise>

A one- or two-character abbreviation for the OP's name.

=item B<#private>

The OP's private flags, rendered with abbreviated names if possible.

=item B<#privval>

The numeric value of the OP's private flags.

=item B<#seq>

The sequence number of the OP. Note that this is a sequence number
generated by B::Concise.

=item B<#opt>

Whether or not the op has been optimised by the peephole optimiser.

=item B<#static>

Whether or not the op is statically defined.  This flag is used by the
B::C compiler backend and indicates that the op should not be freed.

=item B<#sibaddr>

The address of the OP's next youngest sibling, in hexidecimal.

=item B<#svaddr>

The address of the OP's SV, if it has an SV, in hexidecimal.

=item B<#svclass>

The class of the OP's SV, if it has one, in all caps (e.g., 'IV').

=item B<#svval>

The value of the OP's SV, if it has one, in a short human-readable format.

=item B<#targ>

The numeric value of the OP's targ.

=item B<#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.

=item B<#targarglife>

Same as B<#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.

=item B<#typenum>

The numeric value of the OP's type, in decimal.

=back

=head1 ABBREVIATIONS

=head2 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)

=head2 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
    #      PADOP            An OP with a GV on the pad

=head1 Using B::Concise outside of the O framework

You can use B<B::Concise>, and call compile() directly, and
repeatedly.  By doing so, you can avoid the compile-time only
operation of 'perl -MO=Concise ..'.  For example, you can use the
debugger to step through B::Concise::compile() itself.

When doing so, you can alter Concise output by providing new output
styles, and optionally by adding callback routines which populate new
variables that may be rendered as part of those styles.  For all
following sections, please review L</FORMATTING SPECIFICATIONS>.

=head2 Example: Altering Concise Renderings

    use B::Concise qw(set_style add_callback);
    set_style($your_format, $your_gotofmt, $your_treefmt);
    add_callback
      ( sub {
            my ($h, $op, $format, $level, $stylename) = @_;
            $h->{variable} = some_func($op);
        }
      );
    B::Concise::compile(@options)->();

=head2 set_style()

B<set_style> accepts 3 arguments, and updates the three format-specs
comprising a line-style (basic-exec, goto, tree).  It has one minor
drawback though; it doesn't register the style under a new name.  This
can become an issue if you render more than once and switch styles.
Thus you may prefer to use add_style() and/or set_style_standard()
instead.

=head2 set_style_standard($name)

This restores one of the standard line-styles: C<terse>, C<concise>,
C<linenoise>, C<debug>, C<env>, into effect.  It also accepts style
names previously defined with add_style().

=head2 add_style()

This subroutine accepts a new style name and three style arguments as
above, and creates, registers, and selects the newly named style.  It is
an error to re-add a style; call set_style_standard() to switch between
several styles.

=head2 add_callback()

If your newly minted styles refer to any #variables, you'll need to
define a callback subroutine that will populate (or modify) those
variables.  They are then available for use in the style you've chosen.

The callbacks are called for each opcode visited by Concise, in the
same order as they are added.  Each subroutine is passed five
parameters.

  1. A hashref, containing the variable names and values which are
     populated into the report-line for the op
  2. the op, as a B<B::OP> object
  3. a reference to the format string
  4. the formatting (indent) level
  5. the selected stylename

To define your own variables, simply add them to the hash, or change
existing values if you need to.  The level and format are passed in as
references to scalars, but it is unlikely that they will need to be
changed or even used.

=head2 Running B::Concise::compile()

B<compile> accepts options as described above in L</OPTIONS>, and
arguments, which are either coderefs, or subroutine names.

compile() constructs and returns a coderef, which when invoked, scans
the optree, and prints the results to STDOUT.  Once you have the
coderef, you may change the output style; thereafter the coderef renders
in the new style.

B<walk_output> lets you change the print destination from STDOUT to
another open filehandle, or (unless you've built with -Uuseperlio)
into a string passed as a ref.

    walk_output(\my $buf);
    my $walker = B::Concise::compile('-concise','funcName', \&aSubRef);
    print "Concise Banner for Functions: $buf\n";
    $walker->();
    print "Concise Rendering(s)?: $buf\n";

For each subroutine visited by Concise, the $buf will contain a
banner naming the function or coderef about to be traversed.
Once $walker is invoked, it prints the actual renderings for each.

To switch back to one of the standard styles like C<concise> or
C<terse>, call C<set_style_standard>, or pass the style name into
B::Concise::compile() (as done above).

=head2 B::Concise::reset_sequence()

This function (not exported) lets you reset the sequence numbers (note
that they're numbered arbitrarily, their goal being to be human
readable).  Its purpose is mostly to support testing, i.e. to compare
the concise output from two identical anonymous subroutines (but
different instances).  Without the reset, B::Concise, seeing that
they're separate optrees, generates different sequence numbers in
the output.

=head2 Errors

All detected errors, (invalid arguments, internal errors, etc.) are
resolved with a die($message). Use an eval if you wish to catch these
errors and continue processing.

In particular, B<compile> will die if you've asked for a non-existent
function-name, a non-existent coderef, or a non-CODE reference.

=head1 AUTHOR

Stephen McCamant, E<lt>smcc@CSUA.Berkeley.EDUE<gt>.

=cut