B::Concise(e)Perl Programmers Reference GuidB::Concise(e) NAME B::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(s)) 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" perl v5.6.1 2001-02-23 B::Concise(e)