[Perl/perl5] 1ee51d: regexp.h - fixup mistake in comment

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 1ee51d7ef248366649de1c50dafe89b2a2fa7cbb
      https://github.com/Perl/perl5/commit/1ee51d7ef248366649de1c50dafe89b2a2fa7cbb
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexp.h

  Log Message:
  -----------
  regexp.h - fixup mistake in comment

rex->maxlen holds the maximum length the pattern can match, not the
minimum. The copy was obviously copied from the rex->minlen case,
so fix it to be correct.


  Commit: bed264fb59f3f5945dea7f8a1670254c0d59f58c
      https://github.com/Perl/perl5/commit/bed264fb59f3f5945dea7f8a1670254c0d59f58c
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M t/re/regexp.t

  Log Message:
  -----------
  t/re/regexp.t - in skip_amp tests (via _noamp.t) do not TODO tests with ampersand

Tests with $& always pass in regexp_noamp.t (wrapper around regexp.t),
so when they are TODO tests it looks like a TODO pass when in fact it is
just an artifact of how we handle ampersand tests in this file. For these
cases we simply do not mark them as TODO anymore


  Commit: 05b13cf680588a26de64f13d2b3be385e17624bc
      https://github.com/Perl/perl5/commit/05b13cf680588a26de64f13d2b3be385e17624bc
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M pod/perldebguts.pod
    M pp_ctl.c
    M regcomp.c
    M regcomp.h
    M regcomp.sym
    M regcomp_debug.c
    M regexec.c
    M regexp.h
    M regnodes.h
    M t/re/pat.t
    M t/re/re_tests

  Log Message:
  -----------
  regcomp.c - track parens related to CURLYX and CURLYM

This was originally a patch which made somewhat drastic changes to how
we represent capture buffers, which Dave M and I and are still
discussing offline and which has a larger impact than is acceptable to
address at the current time. As such I have reverted the controversial
parts of this patch for now, while keeping most of it intact even if in
some cases the changes are unused except for debugging purposes.

This patch still contains valuable changes, for instance teaching CURLYX
and CURLYM about how many parens there are before the curly[1] (which
will be useful in follow up patches even if stricly speaking they are
not directly used yet), tests and other cleanups. Also this patch is
sufficiently large that reverting it out would have a large effect on
the patches that were made on top of it.

Thus keeping most of this patch while eliminating the controversial
parts of it for now seemed the best approach, especially as some of the
changes it introduces and the follow up patches based on it are very
useful in cleaning up the structures we use to represent regops.

[1] Curly is the regexp internals term for quantifiers, named after
x{min,max} "curly brace" quantifiers.


  Commit: acababb42be12ff2986b73c1bfa963b70bb5d54e
      https://github.com/Perl/perl5/commit/acababb42be12ff2986b73c1bfa963b70bb5d54e
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M pod/perldebguts.pod
    M regcomp.c
    M regcomp.h
    M regcomp.sym
    M regcomp_debug.c
    M regcomp_trie.c
    M regexec.c
    M regexp.h
    M regnodes.h
    M t/re/pat.t
    M t/re/re_tests

  Log Message:
  -----------
  regexec.c - teach BRANCH and BRANCHJ nodes to reset capture buffers

In /((a)(b)|(a))+/ we should not end up with $2 and $4 being set at
the same time. When a branch fails it should reset any capture buffers
that might be touched by its branch.

We change BRANCH and BRANCHJ to store the number of parens before the
branch, and the number of parens after the branch was completed. When
a BRANCH operation fails, we clear the buffers it contains before we
continue on.

It is a bit more complex than it should be because we have BRANCHJ
and BRANCH. (One of these days we should merge them together.)

This is also made somewhat more complex because TRIE nodes are actually
branches, and may need to track capture buffers also, at two levels.
The overall TRIE op, and for jump tries especially where we emulate
the behavior of branches. So we have to do the same clearing logic if
a trie branch fails as well.


  Commit: 38508ce8fc3a1bd12a3bb65e9d4ceb9b396a18db
      https://github.com/Perl/perl5/commit/38508ce8fc3a1bd12a3bb65e9d4ceb9b396a18db
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c
    M regexp.h
    M t/re/re_tests

  Log Message:
  -----------
  regexec.c - incredibly inefficient solution to backref problem

Backrefs to unclosed parens inside of a quantified group were not being
properly handled, which revealed we are not unrolling the paren state properly
on failure and backtracking.

Much of the code assumes that when we execute a "conditional" operation (where
more than one thing could match) that we need not concern ourself with the
paren state unless the conditional operation itself represents a paren, and
that generally opcodes only needed to concern themselves with parens to their
right. When you exclude backrefs from the equation this is broadly reasonable
(i think), as on failure we typically dont care about the state of the paren
buffers. They either get reset as we find a new different accepting pathway,
or their state is irrelevant if the overal match is rejected (eg it fails).

However backreferences are different. Consider the following pattern
from the tests

    "xa=xaaa" =~ /^(xa|=?\1a){2}\z/

in the first iteration through this the first branch matches, and in fact
because the \1 is in the second branch it can't match on the first iteration
at all. After this $1 = "xa". We then perform the second iteration. "xa" does
not match "=xaaa" so we fall to the second branch. The '=?' matches, but sets
up a backtracking action to not match if the rest of the pattern does not
match. \1 matches 'xa', and then the 'a' matches, leaving an unmatched 'a' in
the string, we exit the quantifier loop with $1 = "=xaa" and match \z against
the remaining "a" in the pattern, and fail.

Here is where things go wrong in the old code, we unwind to the outer loop,
but we do not unwind the paren state. We then unwind further into the 2nds
iteration of the loop, to the '=?' where we then try to match the tail with
the quantifier matching the empty string. We then match the old $1 (which was
not unwound) as "=xaa", and then the "a" matches, and we are the end of the
string and we have incorrectly accpeted this string as matching the pattern.

What should have happend was when the \1 was resolved the second time it
should have returned the same string as it did when the =? matched '=', which
then would have resulted in the tail matching again, and etc, eventually
unwinding the entire pattern when the second iteration failed entirely.

This patch is very crude. It simply pushes the state of the parens and creates
an unwind point for every case where we do a transition to a B or _next
operation, and we make the corresponding _next_fail do the appropriate
unwinding. The objective was to achieve correctness and then work towards
making it more efficient. We almost certainly overstore items on the stack.

In the next patch we will keep track of the unclosed parens before the
relevant operators and make sure that they are properly pushed and
unwound at the correct times. In other words this is a first step patch
to make sure things are correct, the next patch will change it so we do
it quickly.


  Commit: 59db194299c94c6707095797c3df0e2f67ff82b2
      https://github.com/Perl/perl5/commit/59db194299c94c6707095797c3df0e2f67ff82b2
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regcomp.c
    M regcomp.h
    M regcomp.sym
    M regcomp_internal.h
    M regexec.c
    M regexp.h
    M regnodes.h

  Log Message:
  -----------
  regexec.c - make REF into a backtracking state

This way we can do the required paren restoration only when it is in use. When
we match a REF type node which is potentially a reference to an unclosed paren
we push the match context information, currently for "everything", but in a
future patch we can teach it to be more efficient by adding a new parameter to
the REF regop to track which parens it should save.

This converts the backtracking changes from the previous commit, so that it is
run only when specifically enabled via the define RE_PESSIMISTIC_PARENS which
is by default 0. We don't make the new fields in the struct conditional as the
stack frames are large and our changes don't make any real difference and it
keeps things simpler to not have conditional members, especially since some of
the structures have to line up with each other.

If enabling RE_PESSIMISTIC_PARENS fixes a backtracking bug then it means
something is sensitive to us not necessarily restoring the parens properly on
failure. We make some assumptions that the paren state after a failing state
will be corrected by a future successful state, or that the state of the
parens is irrelevant as we will fail anyway. This can be made not true by
EVAL, backrefs, and potentially some other scenarios. Thus I have left this
inefficient logic in place but guarded by the flag.


  Commit: 17e3e02ad120eabda2bdb6c297a70d53294437ef
      https://github.com/Perl/perl5/commit/17e3e02ad120eabda2bdb6c297a70d53294437ef
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M embed.fnc
    M embed.h
    M pod/perldebguts.pod
    M proto.h
    M regcomp.c
    M regcomp.h
    M regcomp.sym
    M regcomp_debug.c
    M regcomp_study.c
    M regcomp_trie.c
    M regexec.c
    M reginline.h
    M regnodes.h

  Log Message:
  -----------
  regex engine - simplify regnode structures and make them consistent

This eliminates the regnode_2L data structure, and merges it with the older
regnode_2 data structure. At the same time it makes each "arg" property of the
various regnode types that have one be consistently structured as an anonymous
union like this:

    union {
        U32 arg1u;
        I32 arg2i;
        struct {
            U16 arg1a;
            U16 arg1b;
        };
    };

We then expose four macros for accessing each slot: ARG1u() ARG1i() and
ARG1a() and ARG1b(). Code then explicitly designates which they want. The old
logic used ARG() to access an U32 arg1, and ARG1() to access an I32 arg1,
which was confusing to say the least. The regnode_2L structure had a U32 arg1,
and I32 arg2, and the regnode_2 data strucutre had two I32 args. With the new
set of macros we use the regnode_2 for both, and use the appropriate macros to
show whether we want to signed or unsigned values.

This also renames the regnode_4 to regnode_3. The 3 stands for "three 32-bit
args". However as each slot can also store two U16s, a regnode_3 can hold up
to 6 U16s, or as 3 I32's, or a combination. For instance the CURLY style nodes
use regnode_3 to store 4 values, ARG1i() for min count, ARG2i() for max count
and ARG3a() and ARG3b() for parens before and inside the quantifier.

It also changes the functions reganode() to reg1node() and changes reg2Lanode()
to reg2node(). The 2L thing was just confusing.


  Commit: d78630f1ec4da716988da18d97cb6425388e696c
      https://github.com/Perl/perl5/commit/d78630f1ec4da716988da18d97cb6425388e696c
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M pod/perldebguts.pod
    M regcomp.c
    M regcomp.sym
    M regcomp_debug.c
    M regexec.c
    M regnodes.h
    M t/re/pat_advanced.t

  Log Message:
  -----------
  regcomp.c - extend REF to hold the paren it needs to regcppush

this way we can avoid pushing every buffer, we only need to push
the nestroot of the ref.


  Commit: bf0d793b562c409c3aa940e6ffeeabd655dd49e5
      https://github.com/Perl/perl5/commit/bf0d793b562c409c3aa940e6ffeeabd655dd49e5
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M dump.c
    M regcomp.c
    M regexec.c
    M regexp.h

  Log Message:
  -----------
  regcomp.c - Use RXp_OFFSp() to access offset data

This insulates access to the regexp match offset data so we can
fix the define later and move the offset structure into a new struct.

The RXp_OFFSp() was introduced in a recent commit to deliberately
break anything using RXp_OFFS() directly. It is hard to type
deliberately, nothing but the internals should use it. Everything
else should use one of the wrappers around it.


  Commit: d145af01e2d4aa289de75be69857b583f2e01f0d
      https://github.com/Perl/perl5/commit/d145af01e2d4aa289de75be69857b583f2e01f0d
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexp.h

  Log Message:
  -----------
  regexp.h - standardize macros, and parenthesize parameters

Obviously this isn't required as we build fine. But doing this
future proofs us to other changes.


  Commit: af48a1be21f158a18eb1af0c28a04f9a4f60d981
      https://github.com/Perl/perl5/commit/af48a1be21f158a18eb1af0c28a04f9a4f60d981
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M dump.c
    M regcomp_debug.c
    M regexec.c

  Log Message:
  -----------
  regexec.c - use RXp_LASTPAREN(rex) to access rex->lastparen

This field will be moving to a new struct. Converting this to a macro
will make that move easier.


  Commit: 248ff857d91712060b588bca64bf50790ddcb57b
      https://github.com/Perl/perl5/commit/248ff857d91712060b588bca64bf50790ddcb57b
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexp.h

  Log Message:
  -----------
  regexp.h - add missing defines

We were missing various RXp_XXXX() and RX_XXXX() macros. This adds
them so we can use them in places where we are unreasonable intimate
with the regexp struct internals.


  Commit: 85506c28098a1787408c4fa4a1ec483fd4f1eb04
      https://github.com/Perl/perl5/commit/85506c28098a1787408c4fa4a1ec483fd4f1eb04
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M dump.c

  Log Message:
  -----------
  dump.c - use RXp_ macros to access regexp struct members

We will move some of these members out of the regexp structure
into a new sub structucture. This isolates those changes to the
macro definitions


  Commit: 82e12b9c6eb3d3230bb2c6af8cacaae982efdf5a
      https://github.com/Perl/perl5/commit/82e12b9c6eb3d3230bb2c6af8cacaae982efdf5a
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c

  Log Message:
  -----------
  regexec.c - use RXp_LASTCLOSEPAREN(r) to access r->lastcloseparen

We will move this struct member into a new struct in a future patch,
and using the macros means we can reduce the number of places that
needs to be explcitly aware of the new structure.


  Commit: f6f426df28f9a018241282f0577e05344d5e3633
      https://github.com/Perl/perl5/commit/f6f426df28f9a018241282f0577e05344d5e3633
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c

  Log Message:
  -----------
  regexec.c - use macro to access rex->subbeg

We will move this member to a new struct in the near future,
converting all uses to a macro isolates that change.


  Commit: 3f86b18e5e61915c293e28cf28c8dd9f591c49e9
      https://github.com/Perl/perl5/commit/3f86b18e5e61915c293e28cf28c8dd9f591c49e9
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c

  Log Message:
  -----------
  regexec.c - use RXp_SUBLEN(ret) for ret->sublen

This member of the regexp structure will be moved to a new
structure in the near future. Converting to use the macro
will make this change easier to manage.


  Commit: 76b383619cfe96975b27000c4c244c23f01516fe
      https://github.com/Perl/perl5/commit/76b383619cfe96975b27000c4c244c23f01516fe
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c

  Log Message:
  -----------
  regexec.c - use RXp_SUBOFFSET(rx) instead of rx->suboffset

We will migrate this struct member to a new struct in the near future
this change will make that patch more minimal and hide the gory details.


  Commit: 5c820d0050c12f5113baf93f00be0762dbb60e5a
      https://github.com/Perl/perl5/commit/5c820d0050c12f5113baf93f00be0762dbb60e5a
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c

  Log Message:
  -----------
  regexec.c - use RXp_SUBCOFFSET instead of rx->subcoffset

This member of the regexp struct will soon be migrated to a new
independent structure. This change ensure that when we do the migration
the changes are restricted to the least code possible.


  Commit: 2f31aef63c4a2c6863d88988c8f9550db5483813
      https://github.com/Perl/perl5/commit/2f31aef63c4a2c6863d88988c8f9550db5483813
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regexec.c

  Log Message:
  -----------
  regexec.c - use RXp_SAVED_COPY(rex) instead of rex->saved_copy

We will migrate this member to a new structure in the near future,
wrapping with a macro makes that migration simpler and less invasive.


  Commit: 6b6b3689b8d05608bf090afff941e9cd41a603a8
      https://github.com/Perl/perl5/commit/6b6b3689b8d05608bf090afff941e9cd41a603a8
  Author: Yves Orton <demerphq@gmail.com>
  Date:   2023-03-13 (Mon, 13 Mar 2023)

  Changed paths:
    M regcomp.c

  Log Message:
  -----------
  regcomp.c - use macro wrappers to minimize impact of struct split

We will move various members of the regexp structure to a new
structure which just contains information about the match. Wrapping
the members in the standard macros means that change can be made
less invasive. We already did all of this in regexec.c


Compare: https://github.com/Perl/perl5/compare/1c1829487274...6b6b3689b8d0

• [Perl/perl5] 1ee51d: regexp.h - fixup mistake in comment by Yves Orton via perl5-changes