=head1 DESCRIPTION
-This is not the perldebug(1) manpage, which tells you how to use
+This is not L<perldebug>, which tells you how to use
the debugger. This manpage describes low-level details concerning
the debugger's internals, which range from difficult to impossible
to understand for anyone who isn't incredibly intimate with Perl's guts.
file compiled by Perl. The same is also true for C<eval>ed strings
that contain subroutines, or which are currently being executed.
The $filename for C<eval>ed strings looks like C<(eval 34)>.
-Code assertions in regexes look like C<(re_eval 19)>.
Values in this array are magical in numeric context: they compare
equal to zero only if the line is not breakable.
The same holds for evaluated strings that contain subroutines, or
which are currently being executed. The $filename for C<eval>ed strings
-looks like C<(eval 34)> or C<(re_eval 19)>.
+looks like C<(eval 34)>.
=item *
Each scalar C<${"_<$filename"}> contains C<"_<$filename">. This is
also the case for evaluated strings that contain subroutines, or
which are currently being executed. The $filename for C<eval>ed
-strings looks like C<(eval 34)> or C<(re_eval 19)>.
+strings looks like C<(eval 34)>.
=item *
A hash C<%DB::sub> is maintained, whose keys are subroutine names
and whose values have the form C<filename:startline-endline>.
C<filename> has the form C<(eval 34)> for subroutines defined inside
-C<eval>s, or C<(re_eval 19)> for those within regex code assertions.
+C<eval>s.
=item *
After the rc file is read, the debugger reads the PERLDB_OPTS
environment variable and uses it to set debugger options. The
contents of this variable are treated as if they were the argument
-of an C<o ...> debugger command (q.v. in L<perldebug/Options>).
+of an C<o ...> debugger command (q.v. in L<perldebug/"Configurable Options">).
+
+=head3 Debugger Internal Variables
-=head3 Debugger internal variables
In addition to the file and subroutine-related variables mentioned above,
the debugger also maintains various magical internal variables.
=item *
-C<%DB::dbline>, is an alias for C<%{"::_<current_file"}>, which
+C<%DB::dbline> is an alias for C<%{"::_<current_file"}>, which
contains breakpoints and actions keyed by line number in
the currently-selected file, either explicitly chosen with the
debugger's C<f> command, or implicitly by flow of execution.
=back
-=head3 Debugger customization functions
+=head3 Debugger Customization Functions
Some functions are provided to simplify customization.
Loading DB routines from perl5db.pl patch level 0.94
Emacs support available.
- Enter h or `h h' for help.
+ Enter h or 'h h' for help.
main::(-e:1): 0
DB<1> sub foo { 14 }
By way of demonstration, we present below a laborious listing
resulting from setting your C<PERLDB_OPTS> environment variable to
the value C<f=n N>, and running I<perl -d -V> from the command line.
-Examples use various values of C<n> are shown to give you a feel
-for the difference between settings. Long those it may be, this
+Examples using various values of C<n> are shown to give you a feel
+for the difference between settings. Long though it may be, this
is not a complete listing, but only excerpts.
=over 4
exited Config::FETCH
entering Config::FETCH
-=item 4
+=item 3
in $=main::BEGIN() from /dev/null:0
in $=Config::BEGIN() from lib/Config.pm:2
in $=Config::FETCH(ref(Config), 'osname') from lib/Config.pm:574
in $=Config::FETCH(ref(Config), 'osvers') from lib/Config.pm:574
-=item 6
+=item 4
in $=main::BEGIN() from /dev/null:0
in $=Config::BEGIN() from lib/Config.pm:2
out $=Config::FETCH(ref(Config), 'PERL_VERSION') from lib/Config.pm:574
in $=Config::FETCH(ref(Config), 'PERL_SUBVERSION') from lib/Config.pm:574
-=item 14
+=item 5
in $=main::BEGIN() from /dev/null:0
in $=Config::BEGIN() from lib/Config.pm:2
in $=Config::FETCH('Config=HASH(0x1aa444)', 'baserev') from lib/Config.pm:574
out $=Config::FETCH('Config=HASH(0x1aa444)', 'baserev') from lib/Config.pm:574
-=item 30
+=item 6
in $=CODE(0x15eca4)() from /dev/null:0
in $=CODE(0x182528)() from lib/Config.pm:2
is printed with proper indentation.
-=head1 Debugging regular expressions
+=head1 Debugging Regular Expressions
There are two ways to enable debugging output for regular expressions.
B<-Dr> flag on the command line.
Otherwise, one can C<use re 'debug'>, which has effects at
-compile time and run time. It is not lexically scoped.
+compile time and run time. Since Perl 5.9.5, this pragma is lexically
+scoped.
-=head2 Compile-time output
+=head2 Compile-time Output
The debugging output at compile time looks like this:
- Compiling REx `[bc]d(ef*g)+h[ij]k$'
+ Compiling REx '[bc]d(ef*g)+h[ij]k$'
size 45 Got 364 bytes for offset annotations.
first at 1
rarest char g at 0
42: EXACT <k>(44)
44: EOL(45)
45: END(0)
- anchored `de' at 1 floating `gh' at 3..2147483647 (checking floating)
- stclass `ANYOF[bc]' minlen 7
+ anchored 'de' at 1 floating 'gh' at 3..2147483647 (checking floating)
+ stclass 'ANYOF[bc]' minlen 7
Offsets: [45]
1[4] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 5[1]
0[0] 12[1] 0[0] 6[1] 0[0] 7[1] 0[0] 9[1] 8[1] 0[0] 10[1] 0[0]
The
- anchored `de' at 1 floating `gh' at 3..2147483647 (checking floating)
- stclass `ANYOF[bc]' minlen 7
+ anchored 'de' at 1 floating 'gh' at 3..2147483647 (checking floating)
+ stclass 'ANYOF[bc]' minlen 7
line (split into two lines above) contains optimizer
information. In the example shown, the optimizer found that the match
=item C<anchored(TYPE)>
-If the pattern may match only at a handful of places, (with C<TYPE>
+If the pattern may match only at a handful of places, with C<TYPE>
being C<BOL>, C<MBOL>, or C<GPOS>. See the table below.
=back
If a substring is known to match at end-of-line only, it may be
-followed by C<$>, as in C<floating `k'$>.
+followed by C<$>, as in C<floating 'k'$>.
The optimizer-specific information is used to avoid entering (a slow) regex
engine on strings that will not definitely match. If the C<isall> flag
C< >I<id>: I<TYPE> I<OPTIONAL-INFO> (I<next-id>)
-=head2 Types of nodes
+=head2 Types of Nodes
Here are the possible types, with short descriptions:
- # TYPE arg-description [num-args] [longjump-len] DESCRIPTION
-
- # Exit points
- END no End of program.
- SUCCEED no Return from a subroutine, basically.
-
- # Anchors:
- BOL no Match "" at beginning of line.
- MBOL no Same, assuming multiline.
- SBOL no Same, assuming singleline.
- EOS no Match "" at end of string.
- EOL no Match "" at end of line.
- MEOL no Same, assuming multiline.
- SEOL no Same, assuming singleline.
- BOUND no Match "" at any word boundary
- BOUNDL no Match "" at any word boundary
- NBOUND no Match "" at any word non-boundary
- NBOUNDL no Match "" at any word non-boundary
- GPOS no Matches where last m//g left off.
-
- # [Special] alternatives
- ANY no Match any one character (except newline).
- SANY no Match any one character.
- ANYOF sv Match character in (or not in) this class.
- ALNUM no Match any alphanumeric character
- ALNUML no Match any alphanumeric char in locale
- NALNUM no Match any non-alphanumeric character
- NALNUML no Match any non-alphanumeric char in locale
- SPACE no Match any whitespace character
- SPACEL no Match any whitespace char in locale
- NSPACE no Match any non-whitespace character
- NSPACEL no Match any non-whitespace char in locale
- DIGIT no Match any numeric character
- NDIGIT no Match any non-numeric character
-
- # BRANCH The set of branches constituting a single choice are hooked
- # together with their "next" pointers, since precedence prevents
- # anything being concatenated to any individual branch. The
- # "next" pointer of the last BRANCH in a choice points to the
- # thing following the whole choice. This is also where the
- # final "next" pointer of each individual branch points; each
- # branch starts with the operand node of a BRANCH node.
- #
- BRANCH node Match this alternative, or the next...
-
- # BACK Normal "next" pointers all implicitly point forward; BACK
- # exists to make loop structures possible.
- # not used
- BACK no Match "", "next" ptr points backward.
-
- # Literals
- EXACT sv Match this string (preceded by length).
- EXACTF sv Match this string, folded (prec. by length).
- EXACTFL sv Match this string, folded in locale (w/len).
-
- # Do nothing
- NOTHING no Match empty string.
- # A variant of above which delimits a group, thus stops optimizations
- TAIL no Match empty string. Can jump here from outside.
-
- # STAR,PLUS '?', and complex '*' and '+', are implemented as circular
- # BRANCH structures using BACK. Simple cases (one character
- # per match) are implemented with STAR and PLUS for speed
- # and to minimize recursive plunges.
- #
- STAR node Match this (simple) thing 0 or more times.
- PLUS node Match this (simple) thing 1 or more times.
-
- CURLY sv 2 Match this simple thing {n,m} times.
- CURLYN no 2 Match next-after-this simple thing
- # {n,m} times, set parens.
- CURLYM no 2 Match this medium-complex thing {n,m} times.
- CURLYX sv 2 Match this complex thing {n,m} times.
-
- # This terminator creates a loop structure for CURLYX
- WHILEM no Do curly processing and see if rest matches.
-
- # OPEN,CLOSE,GROUPP ...are numbered at compile time.
- OPEN num 1 Mark this point in input as start of #n.
- CLOSE num 1 Analogous to OPEN.
-
- REF num 1 Match some already matched string
- REFF num 1 Match already matched string, folded
- REFFL num 1 Match already matched string, folded in loc.
-
- # grouping assertions
- IFMATCH off 1 2 Succeeds if the following matches.
- UNLESSM off 1 2 Fails if the following matches.
- SUSPEND off 1 1 "Independent" sub-regex.
- IFTHEN off 1 1 Switch, should be preceded by switcher .
- GROUPP num 1 Whether the group matched.
-
- # Support for long regex
- LONGJMP off 1 1 Jump far away.
- BRANCHJ off 1 1 BRANCH with long offset.
-
- # The heavy worker
- EVAL evl 1 Execute some Perl code.
-
- # Modifiers
- MINMOD no Next operator is not greedy.
- LOGICAL no Next opcode should set the flag only.
-
- # This is not used yet
- RENUM off 1 1 Group with independently numbered parens.
-
- # This is not really a node, but an optimized away piece of a "long" node.
- # To simplify debugging output, we mark it as if it were a node
- OPTIMIZED off Placeholder for dump.
+=for comment
+This table is generated by regen/regcomp.pl. Any changes made here
+will be lost.
+
+=for regcomp.pl begin
+
+ # TYPE arg-description [num-args] [longjump-len] DESCRIPTION
+
+ # Exit points
+
+ END no End of program.
+ SUCCEED no Return from a subroutine, basically.
+
+ # Anchors:
+
+ BOL no Match "" at beginning of line.
+ MBOL no Same, assuming multiline.
+ SBOL no Same, assuming singleline.
+ EOS no Match "" at end of string.
+ EOL no Match "" at end of line.
+ MEOL no Same, assuming multiline.
+ SEOL no Same, assuming singleline.
+ BOUND no Match "" at any word boundary using
+ native charset semantics for non-utf8
+ BOUNDL no Match "" at any locale word boundary
+ BOUNDU no Match "" at any word boundary using
+ Unicode semantics
+ BOUNDA no Match "" at any word boundary using ASCII
+ semantics
+ NBOUND no Match "" at any word non-boundary using
+ native charset semantics for non-utf8
+ NBOUNDL no Match "" at any locale word non-boundary
+ NBOUNDU no Match "" at any word non-boundary using
+ Unicode semantics
+ NBOUNDA no Match "" at any word non-boundary using
+ ASCII semantics
+ GPOS no Matches where last m//g left off.
+
+ # [Special] alternatives:
+
+ REG_ANY no Match any one character (except newline).
+ SANY no Match any one character.
+ CANY no Match any one byte.
+ ANYOF sv Match character in (or not in) this
+ class, single char match only
+ ANYOF_WARN_SUPER sv Match character in (or not in) this
+ class, warn (if enabled) upon matching a
+ char above Unicode max;
+ ANYOF_SYNTHETIC sv Synthetic start class
+
+ POSIXD none Some [[:class:]] under /d; the FLAGS
+ field gives which one
+ POSIXL none Some [[:class:]] under /l; the FLAGS
+ field gives which one
+ POSIXU none Some [[:class:]] under /u; the FLAGS
+ field gives which one
+ POSIXA none Some [[:class:]] under /a; the FLAGS
+ field gives which one
+ NPOSIXD none complement of POSIXD, [[:^class:]]
+ NPOSIXL none complement of POSIXL, [[:^class:]]
+ NPOSIXU none complement of POSIXU, [[:^class:]]
+ NPOSIXA none complement of POSIXA, [[:^class:]]
+
+ CLUMP no Match any extended grapheme cluster
+ sequence
+
+ # Alternation
+
+ # BRANCH The set of branches constituting a single choice are
+ # hooked together with their "next" pointers, since
+ # precedence prevents anything being concatenated to
+ # any individual branch. The "next" pointer of the last
+ # BRANCH in a choice points to the thing following the
+ # whole choice. This is also where the final "next"
+ # pointer of each individual branch points; each branch
+ # starts with the operand node of a BRANCH node.
+ #
+ BRANCH node Match this alternative, or the next...
+
+ # Back pointer
+
+ # BACK Normal "next" pointers all implicitly point forward;
+ # BACK exists to make loop structures possible.
+ # not used
+ BACK no Match "", "next" ptr points backward.
+
+ # Literals
+
+ EXACT str Match this string (preceded by length).
+ EXACTF str Match this non-UTF-8 string (not
+ guaranteed to be folded) using /id rules
+ (w/len).
+ EXACTFL str Match this string (not guaranteed to be
+ folded) using /il rules (w/len).
+ EXACTFU str Match this string (folded iff in UTF-8,
+ length in folding doesn't change if not
+ in UTF-8) using /iu rules (w/len).
+ EXACTFA str Match this string (not guaranteed to be
+ folded) using /iaa rules (w/len).
+ EXACTFU_SS str Match this string (folded iff in UTF-8,
+ length in folding may change even if not
+ in UTF-8) using /iu rules (w/len).
+ EXACTFU_TRICKYFOLD str Match this folded UTF-8 string using /iu
+ rules
+
+ # Do nothing types
+
+ NOTHING no Match empty string.
+ # A variant of above which delimits a group, thus stops optimizations
+ TAIL no Match empty string. Can jump here from
+ outside.
+
+ # Loops
+
+ # STAR,PLUS '?', and complex '*' and '+', are implemented as
+ # circular BRANCH structures using BACK. Simple cases
+ # (one character per match) are implemented with STAR
+ # and PLUS for speed and to minimize recursive plunges.
+ #
+ STAR node Match this (simple) thing 0 or more
+ times.
+ PLUS node Match this (simple) thing 1 or more
+ times.
+
+ CURLY sv 2 Match this simple thing {n,m} times.
+ CURLYN no 2 Capture next-after-this simple thing
+ CURLYM no 2 Capture this medium-complex thing {n,m}
+ times.
+ CURLYX sv 2 Match this complex thing {n,m} times.
+
+ # This terminator creates a loop structure for CURLYX
+ WHILEM no Do curly processing and see if rest
+ matches.
+
+ # Buffer related
+
+ # OPEN,CLOSE,GROUPP ...are numbered at compile time.
+ OPEN num 1 Mark this point in input as start of #n.
+ CLOSE num 1 Analogous to OPEN.
+
+ REF num 1 Match some already matched string
+ REFF num 1 Match already matched string, folded
+ using native charset semantics for non-
+ utf8
+ REFFL num 1 Match already matched string, folded in
+ loc.
+ REFFU num 1 Match already matched string, folded
+ using unicode semantics for non-utf8
+ REFFA num 1 Match already matched string, folded
+ using unicode semantics for non-utf8, no
+ mixing ASCII, non-ASCII
+
+ # Named references. Code in regcomp.c assumes that these all are after
+ # the numbered references
+ NREF no-sv 1 Match some already matched string
+ NREFF no-sv 1 Match already matched string, folded
+ using native charset semantics for non-
+ utf8
+ NREFFL no-sv 1 Match already matched string, folded in
+ loc.
+ NREFFU num 1 Match already matched string, folded
+ using unicode semantics for non-utf8
+ NREFFA num 1 Match already matched string, folded
+ using unicode semantics for non-utf8, no
+ mixing ASCII, non-ASCII
+
+ IFMATCH off 1 2 Succeeds if the following matches.
+ UNLESSM off 1 2 Fails if the following matches.
+ SUSPEND off 1 1 "Independent" sub-RE.
+ IFTHEN off 1 1 Switch, should be preceded by switcher.
+ GROUPP num 1 Whether the group matched.
+
+ # Support for long RE
+
+ LONGJMP off 1 1 Jump far away.
+ BRANCHJ off 1 1 BRANCH with long offset.
+
+ # The heavy worker
+
+ EVAL evl 1 Execute some Perl code.
+
+ # Modifiers
+
+ MINMOD no Next operator is not greedy.
+ LOGICAL no Next opcode should set the flag only.
+
+ # This is not used yet
+ RENUM off 1 1 Group with independently numbered parens.
+
+ # Trie Related
+
+ # Behave the same as A|LIST|OF|WORDS would. The '..C' variants
+ # have inline charclass data (ascii only), the 'C' store it in the
+ # structure.
+
+ TRIE trie 1 Match many EXACT(F[ALU]?)? at once.
+ flags==type
+ TRIEC trie Same as TRIE, but with embedded charclass
+ charclass data
+
+ AHOCORASICK trie 1 Aho Corasick stclass. flags==type
+ AHOCORASICKC trie Same as AHOCORASICK, but with embedded
+ charclass charclass data
+
+ # Regex Subroutines
+ GOSUB num/ofs 2L recurse to paren arg1 at (signed) ofs
+ arg2
+ GOSTART no recurse to start of pattern
+
+ # Special conditionals
+ NGROUPP no-sv 1 Whether the group matched.
+ INSUBP num 1 Whether we are in a specific recurse.
+ DEFINEP none 1 Never execute directly.
+
+ # Backtracking Verbs
+ ENDLIKE none Used only for the type field of verbs
+ OPFAIL none Same as (?!)
+ ACCEPT parno 1 Accepts the current matched string.
+
+ # Verbs With Arguments
+ VERB no-sv 1 Used only for the type field of verbs
+ PRUNE no-sv 1 Pattern fails at this startpoint if no-
+ backtracking through this
+ MARKPOINT no-sv 1 Push the current location for rollback by
+ cut.
+ SKIP no-sv 1 On failure skip forward (to the mark)
+ before retrying
+ COMMIT no-sv 1 Pattern fails outright if backtracking
+ through this
+ CUTGROUP no-sv 1 On failure go to the next alternation in
+ the group
+
+ # Control what to keep in $&.
+ KEEPS no $& begins here.
+
+ # New charclass like patterns
+ LNBREAK none generic newline pattern
+
+ # SPECIAL REGOPS
+
+ # This is not really a node, but an optimized away piece of a "long"
+ # node. To simplify debugging output, we mark it as if it were a node
+ OPTIMIZED off Placeholder for dump.
+
+ # Special opcode with the property that no opcode in a compiled program
+ # will ever be of this type. Thus it can be used as a flag value that
+ # no other opcode has been seen. END is used similarly, in that an END
+ # node cant be optimized. So END implies "unoptimizable" and PSEUDO
+ # mean "not seen anything to optimize yet".
+ PSEUDO off Pseudo opcode for internal use.
+
+=for regcomp.pl end
=for unprinted-credits
Next section M-J. Dominus (mjd-perl-patch+@plover.com) 20010421
C<0[0]> items indicate that there is no corresponding node.
-=head2 Run-time output
+=head2 Run-time Output
First of all, when doing a match, one may get no run-time output even
if debugging is enabled. This means that the regex engine was never
If the regex engine was entered, the output may look like this:
- Matching `[bc]d(ef*g)+h[ij]k$' against `abcdefg__gh__'
+ Matching '[bc]d(ef*g)+h[ij]k$' against 'abcdefg__gh__'
Setting an EVAL scope, savestack=3
2 <ab> <cdefg__gh_> | 1: ANYOF
3 <abc> <defg__gh_> | 11: EXACT <d>
The I<TYPE> info is indented with respect to the backtracking level.
Other incidental information appears interspersed within.
-=head1 Debugging Perl memory usage
+=head1 Debugging Perl Memory Usage
Perl is a profligate wastrel when it comes to memory use. There
is a saying that to estimate memory usage of Perl, assume a reasonable
The switch was used to track Perl's memory allocations and possible
memory leaks. These days the use of malloc debugging tools like
F<Purify> or F<valgrind> is suggested instead. See also
-L<perlhack/PERL_MEM_LOG>.
+L<perlhacktips/PERL_MEM_LOG>.
One way to find out how much memory is being used by Perl data
structures is to install the Devel::Size module from CPAN: it gives
and total_size().
If Perl has been compiled using Perl's malloc you can analyze Perl
-memory usage by setting the $ENV{PERL_DEBUG_MSTATS}.
+memory usage by setting $ENV{PERL_DEBUG_MSTATS}.
=head2 Using C<$ENV{PERL_DEBUG_MSTATS}>
In a Perl built for debugging, some buckets may have negative usable
size. This means that these buckets cannot (and will not) be used.
For larger buckets, the memory footprint may be one page greater
-than a power of 2. If so, case the corresponding power of two is
+than a power of 2. If so, the corresponding power of two is
printed in the C<APPROX> field above.
=item Free/Used
free: 8 16 32 64 128 256 512 1024 2048 4096 8192
4 12 24 48 80
-With non-C<DEBUGGING> perl, the buckets starting from C<128> have
+With a non-C<DEBUGGING> perl, the buckets starting from C<128> have
a 4-byte overhead, and thus an 8192-long bucket may take up to
8188-byte allocations.
https://perl5.git.perl.org / perl5.git / blobdiff