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[Perl/perl5] 88e42c: add PERL_RC_STACK define (not yet defined)

From:
iabyn via perl5-changes
Date:
March 12, 2023 15:34
Subject:
[Perl/perl5] 88e42c: add PERL_RC_STACK define (not yet defined)
Message ID:
Perl/perl5/push/refs/heads/smoke-me/davem/rc_stack2/b7ef17-dec99a@github.com
  Branch: refs/heads/smoke-me/davem/rc_stack2
  Home:   https://github.com/Perl/perl5
  Commit: 88e42cabb3014a9bf89b5c9b67d38934fac1cc63
      https://github.com/Perl/perl5/commit/88e42cabb3014a9bf89b5c9b67d38934fac1cc63
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M perl.c
    M perl.h

  Log Message:
  -----------
  add PERL_RC_STACK define (not yet defined)

This macro turns on stack reference counting.
Add the macro, but commented out for now.

In addition, temporarily define and enable PERL_XXX_TMP_NORC.

This is a temporary transition measure: even in the presence of
PERL_RC_STACK, do not actually modify reference counts yet. So
PERL_RC_STACK will still define all the new static functions and code
behaviour, except for the bits that actually modify reference counts in
ways that assume the stack is reference counted. It allows this branch
to have many commits which incrementally deal with adding support for
PERL_RC_STACK, with each individual commit still working while half of
the core is still not yet "ref count aware".


  Commit: 01f4102bef86e64a4b68343c44887395a67e63f4
      https://github.com/Perl/perl5/commit/01f4102bef86e64a4b68343c44887395a67e63f4
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M lib/Internals.pod
    M universal.c

  Log Message:
  -----------
  add Internals::stack_refcounted()

This indicates whether perl has been built with PERL_RC_STACK.
For now this should only be used by core; It's not yet decided whether
CPAN modules have a use case too.


  Commit: b51ebc11ebe7ebad17c23ff42e7ec494da9e8c1f
      https://github.com/Perl/perl5/commit/b51ebc11ebe7ebad17c23ff42e7ec494da9e8c1f
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M ext/Devel-Peek/t/Peek.t

  Log Message:
  -----------
  ext/Devel-Peek/t/Peek.t: fixup top refcount

There are a few 'expected' Dump() output patterns which expect the
refcount of the top-most SV in the tree to be fixed number like

    REFCNT = 1

Change all those occurrences to

    REFCNT = \d+

or similar, since a reference-counted stack will cause higher values


  Commit: 5ca6ca44451c030bea5976d9d62a662b2ea455f6
      https://github.com/Perl/perl5/commit/5ca6ca44451c030bea5976d9d62a662b2ea455f6
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c
    M scope.c

  Log Message:
  -----------
  pp_dbstate: skip SAVESTACK_POS()

On PERL_RC_STACK builds, skip the call to SAVESTACK_POS().
I suspect that saving the stack position is no longer
required. It was added in 5.001 by:

    NETaa13155: &DB::DB left trash on the stack.
    From: Thomas Koenig
    Files patched: lib/perl5db.pl pp_ctl.c
     The call by pp_dbstate() to &DB::DB left trash on the
     stack.  It now calls DB in list context, and DB returns
     ().

but the details of what bug it fixed are long lost to history.
SAVESTACK_POS() doesn't work well with stacks which may be split into
partly reference-counted and partly not halves, so skip it and hope it
doesn't cause any problems.

Also, assert that SAVEt_STACK_POS isn't used anywhere any more.


  Commit: bc8cade049956dd77a028331201b31b57401245d
      https://github.com/Perl/perl5/commit/bc8cade049956dd77a028331201b31b57401245d
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  pp_mapwhile(): null out holes in stack

From time to time, pp_mapwhile() shifts up any remaining args on the
stack, in order to leave enough space to add the current results to any
accumulated results. This leaves a hole in the stack, which might not be
fully filled until the last iteration. As well as making the output of
perl -Ds confusing, any garbage left in the hole will double-count
towards the reference count of each SV once the stack becomes
reference-counted.

So fill the newly-created hole in the stack with NULL pointers.


  Commit: 5d9fa7569adf1750d974a8769557e36ad8f62b1c
      https://github.com/Perl/perl5/commit/5d9fa7569adf1750d974a8769557e36ad8f62b1c
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M av.c
    M embed.fnc
    M embed.h
    M inline.h
    M proto.h

  Log Message:
  -----------
  Add av_remove_offset() core-only function

This function abstracts away removing any AvARRAY(av) - AvALLOC(av)
offset from an array (previously added by av_shift()).

Also use Zero() rather than a loop to NULL out any elements in the
offset area.


  Commit: a30c57ece14be925f271f65adacde52dd31592be
      https://github.com/Perl/perl5/commit/a30c57ece14be925f271f65adacde52dd31592be
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M embed.fnc
    M embed.h
    M op.c
    M perl.c
    M pp_ctl.c
    M proto.h

  Log Message:
  -----------
  create_eval_scope(): parameterise the stack pos

Rather than always using PL_stack_sp to pass to cx_pushblock(),
allow the caller of create_eval_scope() to specify what stack position
is to be saved.

This will be used shortly to fix a bug.


  Commit: b982e43e22c6ae39bb78575541061256a3d3e5cf
      https://github.com/Perl/perl5/commit/b982e43e22c6ae39bb78575541061256a3d3e5cf
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M perl.c

  Log Message:
  -----------
  Perl_call_sv(G_EVAL): set oldsp correctly

call_sv(cv, G_EVAL) pushes a CXt_EVAL context, fakes up an entersub op,
then runs it, letting entersub consume the arguments pushed onto the current
stack frame by call_sv()'s caller.

So the C-level

    PUSHMARK():
    PUSHs(arg1);
    ...
    PUSHs(argN);
    call_sv(cv, G_EVAL);

is about equivalent to the perl-level:

    eval { cv($arg1,..$argN) }

Except that in the latter, when the CXt_EVAL is pushed, it is done
*before* any of the arguments have been pushed, so the eval context's
blk_oldsp points to just before the arguments. Conversely in the case of
call_sv(), blk_oldsp gets set to just *after* the arguments.

During an exception, the context stack gets unwound until the CXt_EVAL
is reached, then PL_stack_sp is restored to the blk_oldsp value.

The difference currently makes no real functional difference, as
call_sv() resets PL_stack_sp immediately after an exception anyway, so
the bad just-restored value is discarded. But it does mean that
PL_stack_sp briefly points to junk on the stack. When the stack becomes
reference-counted, this will start to become important. So fix now.

This commit changes it so that call_sv()'s blk_oldsp gets set to just
before the arguments too. It also asserts that the stack was cleared
back to blk_oldsp.


  Commit: f3eb54d083308235bf24327ec9f2b53bcb7a3e10
      https://github.com/Perl/perl5/commit/f3eb54d083308235bf24327ec9f2b53bcb7a3e10
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M inline.h

  Log Message:
  -----------
  assert that cxstack[i].oldsp are increasing

The saved stack positions

    cxstack[0].oldsp
    cxstack[1].oldsp
    cxstack[2].oldsp
    ...

effectively divide the argument stack into a series of stack frames.
This unravels if an earlier oldsp is actually greater than a later one.
It didn't really matter before, but for a reference-counted stack it
becomes a mess when trying to unwind the stack after an exception.  So
assert that oldsp never decreases.

This assert found one failure in core, which was fixed by the previous
commit.


  Commit: 123ace4431a8024587994f12eee751714db03372
      https://github.com/Perl/perl5/commit/123ace4431a8024587994f12eee751714db03372
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M autodoc.pl
    M embed.fnc
    M embed.h
    M inline.h
    M proto.h

  Log Message:
  -----------
  add rpp_foo() refcounted-stack manipulation fns

The various new inline functions like rpp_push_1() are intended to be
(approximate) replacements for the traditional PUSHs(), POPs() etc
macros, except that when compiled under PERL_RC_STACK, they understand
a reference-counted stack.

Except currently they assume the stack is still not reference-counted in
the presence of PERL_XXX_TMP_NORC. This will be turned off in a few
commits' time.


  Commit: b4cd9999dfab482fb84fafbb2ebaa2767e347fb5
      https://github.com/Perl/perl5/commit/b4cd9999dfab482fb84fafbb2ebaa2767e347fb5
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_hot.c

  Log Message:
  -----------
  use new rpp_is_lone() function

This inline function checks for whether an SV is only referenced
from the stack or temps stack. (Well, it only checks TEMPs currently, but
will shortly handle a ref-counted stack too). In particular it tests for:

    SvTEMP(sv) && && SvREFCNT(sv) == 1

This commit uses it in various places to replace where the conditions
are currently written out in full. This will allow those places to still
work correctly when the stack becomes reference-counted.


  Commit: 9357da45711359bad23fc98fac9ab48c1fd2e2c8
      https://github.com/Perl/perl5/commit/9357da45711359bad23fc98fac9ab48c1fd2e2c8
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M doop.c
    M embed.fnc
    M makedef.pl
    M pp.c
    M pp.h
    M pp_ctl.c
    M pp_hot.c
    M pp_pack.c
    M pp_sys.c
    M proto.h

  Log Message:
  -----------
  wrap normal non-RC-stack-aware pp functions

In the presence of PERL_RC_STACK, wrap most pp functions with a function
that calls the real pp function with a (non-reference-counted) copy of
the stack arguments.  On return, the wrapper bumps up the reference
count of the returned list and, as appropriate, shifts them down the
stack.

This allows a pp function which is not aware of a reference-counted
stack to be called in a reference-counted stack environment.

About 250 such functions are wrappable; the remaining 50 or so need
individual handling and will be dealt with in the following few commits.

This is a temporary band-aid which slows down calls to pp() functions.
It is expected that over time these functions will be unwrapped and
updated to to understand a reference-counted stack. But by temporarily
wrapping them now, it allows perl to be (experimentally) shifted over to
a reference-counted stack without having to review and modify all 30K
lines of pp code first.

(Except currently, the wrapper assumes the stack is still not
reference-counted in the presence of PERL_XXX_TMP_NORC. This will be
turned off in a few commits' time.)

Note also that pp_wrap() is not yet complete. It simulates wrapping by
making a copy of the args on entry to the wrapped function and shifting
any returned values back down. But as well as being temporarily
inhibited from actually modifying reference counts by PERL_XXX_TMP_NORC,
there are extra considerations which will be taken account of by the
"Allow stacks to be reference-counted" commit coming later.


  Commit: cce48df17905f99f84827f2f89c8686f868b1c84
      https://github.com/Perl/perl5/commit/cce48df17905f99f84827f2f89c8686f868b1c84
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_hot.c

  Log Message:
  -----------
  pp_method*: fixup wrapping

The various method ops are sometimes naughty and substitute a different
object at the base of the current stack frame. This is "below"
the area of the stack normally processed by pp_wrap(), so the reference
count adjusting must be done manually.


  Commit: b5ec57a19f8ab3f75f662dff0fbc4c9e5b097355
      https://github.com/Perl/perl5/commit/b5ec57a19f8ab3f75f662dff0fbc4c9e5b097355
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: regcomp

Update pp_regcomp() to handle a reference-counted stack environment in
the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 48c0c27ad34b07c5cf25a0c3ef4368b1cad33238
      https://github.com/Perl/perl5/commit/48c0c27ad34b07c5cf25a0c3ef4368b1cad33238
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M embed.fnc
    M makedef.pl
    M pp_hot.c
    M proto.h

  Log Message:
  -----------
  make RC-stack-aware: entersub

Update pp_entersub() to handle a reference-counted stack environment in
the presence of PERL_RC_STACK.

As well as the expected changes to pp_entersub(), this commit also adds
a function, xs_wrap(),  which is similar in concept to pp_wrap(), but
which makes a non-reference-counted copy of the arguments on the stack
before calling any XS function which isn't RC-stack-aware yet (which is
currently all of them).

xs_wrap() will soon be used by pp_goto() too.

In the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.

Note also that xs_wrap() is not yet complete. It simulates wrapping by
making a copy of the args on entry to the wrapped function and shifting
any returned values back down. But as well as being temporarily
inhibited from actually modifying reference counts by PERL_XXX_TMP_NORC,
there are extra considerations which will be taken account of by the
"Allow stacks to be reference-counted" commit coming later.


  Commit: 14754902b832cbbf4683a91cc7f0f6ed5200a38e
      https://github.com/Perl/perl5/commit/14754902b832cbbf4683a91cc7f0f6ed5200a38e
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c
    M pp_hot.c

  Log Message:
  -----------
  make RC-stack-aware: db/nextstate, unstack

Update pp_dbstate(), pp_nextstate() and pp_unstack() to handle a
reference-counted stack environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 7cd8b08042b3af1d0da5170c60dea5d37fc9fbca
      https://github.com/Perl/perl5/commit/7cd8b08042b3af1d0da5170c60dea5d37fc9fbca
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c
    M pp_hot.c
    M t/op/grep.t

  Log Message:
  -----------
  make RC-stack-aware: map and grep

Update pp_grepstart(), pp_grepwhile() and pp_mapwhile() to handle a
reference-counted stack environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.

Also add some tests to op/grep.t to check for stuff being freed at an
appropriate time  (they weren't being at one iteration of this commit).


  Commit: c46b1b62101cbcb48f602d297693afab79f673cc
      https://github.com/Perl/perl5/commit/c46b1b62101cbcb48f602d297693afab79f673cc
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: enteriter, leaveloop

Update pp_enteriter() and pp_leveloop() to handle a reference-counted
stack environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 9d50ae44399985f194312f33eff5d2619cc5b156
      https://github.com/Perl/perl5/commit/9d50ae44399985f194312f33eff5d2619cc5b156
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c
    M pp_hot.c

  Log Message:
  -----------
  make RC-stack-aware: pp_leavefoo()

Update some pp_leavefoo() functions to handle a reference-counted stack
environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: b0caee230a8e6d5ff5bd4a25d8d6c4ada2a51bf7
      https://github.com/Perl/perl5/commit/b0caee230a8e6d5ff5bd4a25d8d6c4ada2a51bf7
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: last

Update pp_last() to handle a reference-counted stack environment in
the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 0ba3c6c4e988f00ab2695a3da8e01ead63c09b22
      https://github.com/Perl/perl5/commit/0ba3c6c4e988f00ab2695a3da8e01ead63c09b22
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: goto

Update pp_goto() to handle a reference-counted stack environment in
the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 2be47c88447a9cc290e6120a8301f526c16175eb
      https://github.com/Perl/perl5/commit/2be47c88447a9cc290e6120a8301f526c16175eb
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: require,eval

Update pp_entereval() et al to handle a reference-counted stack
environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 694187e9dd3c1bd912c359c302082117defaf8f7
      https://github.com/Perl/perl5/commit/694187e9dd3c1bd912c359c302082117defaf8f7
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: enter/leavegiven etc

Update pp_entrgiven() et al to handle a reference-counted stack
environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 93fa2b80c1bccfe6c9730a21fdd3b88b192a3356
      https://github.com/Perl/perl5/commit/93fa2b80c1bccfe6c9730a21fdd3b88b192a3356
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_sys.c

  Log Message:
  -----------
  make RC-stack-aware: enter/leavewrite

Update pp_enterwrite() and pp_leavewrite() to handle a reference-counted
stack environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: b16c0f137d26ed3620cd69385b9822faef8f9c8d
      https://github.com/Perl/perl5/commit/b16c0f137d26ed3620cd69385b9822faef8f9c8d
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_sort.c
    M t/op/sort.t

  Log Message:
  -----------
  make RC-stack-aware: pp_sort()

Update pp_sort() to handle a reference-counted stack environment in
the presence of PERL_RC_STACK.

(But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.)

In addition to replacing all the POPs type stuff with rpp_foo() inline
function calls, three slight functional changes were done to make this
work.

1) The stack entry pointing to the SV containing the sort function name
   is now NULLed out rather than being left on the stack, just after
   being freed. It is usually overwritten later on in the process.
2) For an in-place sort (@a = sort @a), the AV is now left on the stack
   so that it isn't prematurely freed. This is okay, because...
3) Also for an in-place sort, after the results are stored in @a, the
   stack frame is cleared. This is safe because the optimisation is
   only ever done in void context. Previously the stack would be be
   cleared by the following nextstate op or similar anyway.


  Commit: 7c127b93aa22c9ba32cd2c16a36613e1637a0a17
      https://github.com/Perl/perl5/commit/7c127b93aa22c9ba32cd2c16a36613e1637a0a17
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_sort.c

  Log Message:
  -----------
  make RC-stack-aware: sort cmp function invokers

Update S_sortcv() etc to handle a reference-counted stack environment in
the presence of PERL_RC_STACK.

These three static functions are used by pp_sort() to invoke a suitable
comparison subroutine.

(But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.)


  Commit: 433179a9529f3bfe5eccfb9c53565bed36689d44
      https://github.com/Perl/perl5/commit/433179a9529f3bfe5eccfb9c53565bed36689d44
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M doio.c
    M pp_sys.c

  Log Message:
  -----------
  make RC-stack-aware: stat and filetest ops

Update the pp functions which do stat and filetest operations to handle
a reference-counted stack environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 9e328ad54f7d4034265f1c1b696e81417e6d9bc6
      https://github.com/Perl/perl5/commit/9e328ad54f7d4034265f1c1b696e81417e6d9bc6
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M inline.h
    M pp.c

  Log Message:
  -----------
  make RC-stack-aware: misc pp() functions

Update the remaining miscellaneous pp() functions to handle a
reference-counted stack environment in the presence of PERL_RC_STACK.

But in the presence of PERL_XXX_TMP_NORC, don't actually manipulate
reference counts yet. This will be turned off in a few commits' time.


  Commit: 56b7945f56e9f2e489a4ea91136b7b60dda38701
      https://github.com/Perl/perl5/commit/56b7945f56e9f2e489a4ea91136b7b60dda38701
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M perl.c

  Log Message:
  -----------
  make RC-stack-aware: call_sv() and similar

Update the functions which directly or indirectly call a CV, to handle
a reference-counted stack environment.

Note that call_sv(), eval_pv() etc are slightly unusual in that they can
be called from either a reference-counted or non-RC stack environment,
so must be able to handle either case. This is done mostly by relying on
CALLRUNOPS() to fix things up, but for anything pushed/pulled around
that, by checking rpp_stack_is_rc(): which currently always returns
false, but once ref-counting is enabled in a few commits' time, may
start returning true.


  Commit: 2d57ae3e9fc7d290a01f360b681c034713df4775
      https://github.com/Perl/perl5/commit/2d57ae3e9fc7d290a01f360b681c034713df4775
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M perl.c

  Log Message:
  -----------
  make RC-stack-aware: eval_sv()

Similar to the previous commit which fixed up call_sv() and similar,
the commit updates eval_sv() to handle a reference-counted stack
environment.

Note that these functions are slightly unusual in that they can
be called from either a reference-counted or non-RC stack environment,
so must be able to handle either case. This is done mostly by relying on
CALLRUNOPS() to fix things up, but for anything pushed/pulled around
that, by checking rpp_stack_is_rc(): which currently always returns
false, but once ref-counting is enabled in a few commits' time, may
start returning true.


  Commit: 20087e20a47b790554eb2ca5988785e70936062b
      https://github.com/Perl/perl5/commit/20087e20a47b790554eb2ca5988785e70936062b
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  make RC-stack-aware: defer

The defer keyword saves the address of an optree, which is then
run during leave_scope(). Since that can happen in unpredictable
places (e.g. during a croak), we won't know until runtime where the
stack is currently reference-counted. So handle both cases.


  Commit: a8c6dd0ea060ae55e4ad4b587f6f499d642066e6
      https://github.com/Perl/perl5/commit/a8c6dd0ea060ae55e4ad4b587f6f499d642066e6
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_hot.c

  Log Message:
  -----------
  make RC-stack-aware: unwrap pp_add()

Remove the temporary wrapper from pp_add() and update it to directly
work in a refcounted-stack environment.

This is mainly a proof of concept to check that all the new rpp_foo()
inline functions and macros are suitable for working with a typical
binary operator.


  Commit: 9e8aeaf539704c6955bc9e34282372604b544083
      https://github.com/Perl/perl5/commit/9e8aeaf539704c6955bc9e34282372604b544083
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp.c

  Log Message:
  -----------
  make RC-stack-aware: unwrap pp_not()

Remove the temporary wrapper from pp_not() and update it to directly
work in a refcounted-stack environment.

This is mainly a proof of concept to check that rpp_tryAMAGICun_MG() and
its underlying Perl_try_amagic_un() work ok.


  Commit: 52416c4e5adde71410c7d5663a90655be1b0a872
      https://github.com/Perl/perl5/commit/52416c4e5adde71410c7d5663a90655be1b0a872
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M op.c

  Log Message:
  -----------
  make RC-stack-aware: S_fold_constants()

The folded SV it pops off the stack should be treated as
reference counted.


  Commit: 823778103757ea4df4f5ecda9b5993ccdf329d8d
      https://github.com/Perl/perl5/commit/823778103757ea4df4f5ecda9b5993ccdf329d8d
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M ext/Devel-Peek/Peek.pm
    M ext/Devel-Peek/Peek.xs

  Log Message:
  -----------
  make RC-stack-aware: Devel::Peek::Dump()

This function is implemented as a custom op rather than as a function
call, so it wasn't getting wrapped for reference-count purposes by
either pp_wrap() nor xs_wrap().

This commit makes it directly handle a reference-counted stack.

This was a particularly confusing one, as a failing test in t/op/eval.t
was reduced to

    use Devel::Peek;
    Dump($@);
    eval { die "boo\n"; };
    Dump($@);

which showed the ref count of $@ increasing after the eval {}. But it
was actually Dump(), not eval{} which was messing with the ref count.


  Commit: 3356a9785a125201e4f5522f892b4a484852ead1
      https://github.com/Perl/perl5/commit/3356a9785a125201e4f5522f892b4a484852ead1
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M sv.c

  Log Message:
  -----------
  make RC-stack-aware: perl_clone()

It has some code that calls out to PACKAGE::CLONE(). Depending on how
the interpreter is being cloned, the code which assembles the args on
the stack for the CLONE() call may be operating on either a
reference-counted stack, or a non-RC one. So handle both cases


  Commit: ed2756e28d0c71b7551c4ae34f83990cd2a42145
      https://github.com/Perl/perl5/commit/ed2756e28d0c71b7551c4ae34f83990cd2a42145
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M gv.c

  Log Message:
  -----------
  make RC-stack-aware: Perl_try_amagic_un() & _bin()

Note that these two functions may be called both from PP functions aware
of a reference-counted stack and from wrapped (non-aware) functions,
hence the RC manipulation is runtime conditional.


  Commit: bb3b7fcdbefad8b209926ec2d312f6789048b9a3
      https://github.com/Perl/perl5/commit/bb3b7fcdbefad8b209926ec2d312f6789048b9a3
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M dist/threads/lib/threads.pm
    M dist/threads/threads.xs

  Log Message:
  -----------
  make RC-stack-aware: threads.xs

S_ithread_run() starts running a new top-level perl interpreter, which
will have a ref-counted stack. So treat the stack a ref-counted.


  Commit: aeb4fdf481da43f0bf6ab3a726a7ef55c416c0fe
      https://github.com/Perl/perl5/commit/aeb4fdf481da43f0bf6ab3a726a7ef55c416c0fe
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M t/cmd/for.t

  Log Message:
  -----------
  make RC-stack-aware: t/cmd/for.t

A test that expects to fail on a non reference-counted stack should no
longer do so if the stack is fully reference-counted


  Commit: 1f12980b96d3e2a1d7cb1af9d9149a8f2a9af50b
      https://github.com/Perl/perl5/commit/1f12980b96d3e2a1d7cb1af9d9149a8f2a9af50b
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M op.c

  Log Message:
  -----------
  make RC-stack-aware: invoking DB::postponed()

Various places in core call DB::postponed(). This all happens in
places where the stack will be reference-counted, so fix the callers.


  Commit: 4394828482590565ba5db8476176bf1ef7b6f384
      https://github.com/Perl/perl5/commit/4394828482590565ba5db8476176bf1ef7b6f384
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M ext/XS-APItest/APItest.xs
    M ext/XS-APItest/t/magic.t

  Log Message:
  -----------
  make RC-stack-aware: ext/XS-APItest/

APItest.xs mainly consists of XS functions - which are not aware of a
ref counted stack - but such functions are called via xs_wrap(), so
that's ok.

However, THX_pp_establish_cleanup() is actually a PP function attached
to an op, rather than an XS function - so it doesn't get automatically
wrapped. Update it to handle a reference-counted stack.

Also, use the standard CALLRUNOPS() macro to call a runos loop rather
than invoking directly; the former will allow a wrapper to be inserted.

Finally, parameterise the expected ref count in t/magic.t, as it will
change if the stack is ref counted.


  Commit: f47d27efd6248715d4c8927d36d27bcb35784f62
      https://github.com/Perl/perl5/commit/f47d27efd6248715d4c8927d36d27bcb35784f62
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M av.c
    M inline.h
    M pp_hot.c

  Log Message:
  -----------
  make shift(@a) leave old pointer

Generally shifting is done by adjusting the start position of the
array, so that AvALLOC() and AvARRAY() no longer align. Previously if
the array was AvREAL(), perl NULL-ed out the old pointer at the same
time, i.e. doing the equivalent of AvARRAY(av)[-1] = NULL.

This commit changes it so that on PERL_RC_STACK builds, perl instead
keeps the old pointer there on AvREAL() arrays too, even if it now
points to a freed SV; and instead makes av_clear() and av_unshift()
responsible for NULL-ing out the slot only when actually reclaiming any
unused slots between AvALLOC() and AvARRAY().

The reason for this is because of the mechanism whereby @DB::args is
sometimes populated by caller(), as used by Carp.pm to display function
arguments in stack traces etc. For the common idiom of

    sub f {
        my $self = shift;
        ....;
    }

then previously, since @_ wasn't AvREAL(), the old pointer in @_ to
argument 0 was kept around and thus the hidden pointer value was still
available for caller() to add to @DB::args.

But since the next commit will change @_ to be AvREAL(), this will no
longer work.  Thus to keep the ability to debug stack traces etc (via
the awful @DB::args hack), we make shift keep the pointer even for the
AvREAL() case.


  Commit: 705145e20b0ba3fec74625c9af5edcefb927c8c1
      https://github.com/Perl/perl5/commit/705145e20b0ba3fec74625c9af5edcefb927c8c1
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M cop.h
    M embed.fnc
    M embed.h
    M inline.h
    M pad.c
    M pp_ctl.c
    M pp_hot.c
    M pp_sort.c
    M proto.h
    M t/op/sub.t

  Log Message:
  -----------
  make @_ AvREAL() on RC-stack

Traditionally, the @_ AV has been marked as AvREAL_off(), but AvREIFY_on().

This commit changes it so that on PERL_RC_STACK builds, @_ is AvREAL().
This will mean that when the stack is ref-counted, the stack frame can
be directly moved to @_ while maintaining the correct ref count for each
argument (in the same way that !AvREAL() worked well with a
non-ref-counted stack).

Note that the stack will not actually be reference-counted for a few
more commits yet. In the meantime, this commit allows for that by
bumping up the reference count of SVs being transferred from the stack
to @_. This extra step will soon be skipped.


  Commit: 4ee800aedb2fde1d83e339def8dce84f51388503
      https://github.com/Perl/perl5/commit/4ee800aedb2fde1d83e339def8dce84f51388503
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M cop.h
    M embed.fnc
    M embed.h
    M inline.h
    M pp.h
    M pp_sort.c
    M proto.h

  Log Message:
  -----------
  add switch_argstack(), push/pop_stackinfo() fns

These new inline functions are supposed to be near-identical
replacements for these macros:

    PUSHSTACKi(type)     push_stackinfo(type)
    POPSTACK()           pop_stackinfo()
    SWITCHSTACK(from,to) switch_argstack(to) // assumes (from == PL_curstack)

except that they don't require dSP to be in scope (they operate on
PL_stack_sp rather than sp) and their names more clearly specify what
sort of stack they manipulate.

The macros are now thin wrappers around the functions. I've kept most of
their uses in core for now as they are still used in places with dSP
present.


  Commit: 427e42366bfdca23eebbaa8eda3d34b3e9dee036
      https://github.com/Perl/perl5/commit/427e42366bfdca23eebbaa8eda3d34b3e9dee036
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M cop.h
    M embed.fnc
    M embed.h
    M inline.h
    M perl.c
    M pp_sort.c
    M proto.h
    M scope.c

  Log Message:
  -----------
  allow argument stack to be AvREAL()

Add a _flags() variant of new_stackinfo() which indicates whether the
new stack AV should be created real or not.

Modify the new push_stackinfo() function to have a similar flag.

Then make the backcompat macros like PUSHSTACKi() still push a non-real
stack, while functions which have been updated to use the new
push_stackinfo() etc will be able get a real AV. The next commit makes
use of that.

This means that existing code (core and XS) which hasn't been updated to
the new ref-counted stack regime can do stuff like:

    PUSHSTACKi(FOO);
    PUSHMARK(sp)
    XPUSHs(sv);
    call_sv();

where call_sv() (or rather, the runops loop it invokes) will be able to
determine that it's been called from a non-RC environment and that the
args on the stack aren't reference-counted.

The next commit will update the runops loops etc to do exactly that.


  Commit: 75d3a9c5b534d0f481c26c3d766c41952e023a88
      https://github.com/Perl/perl5/commit/75d3a9c5b534d0f481c26c3d766c41952e023a88
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M cop.h
    M embed.fnc
    M embed.h
    M inline.h
    M makedef.pl
    M perl.c
    M perl.h
    M pp_ctl.c
    M pp_hot.c
    M pp_pack.c
    M pp_sort.c
    M proto.h
    M run.c
    M scope.c
    M sv.c

  Log Message:
  -----------
  Allow argument stacks to be reference-counted

When built with PERL_RC_STACK, this substantial commit:

* makes stacks AvREAL() by default.
* adds the si_stack_nonrc_base field to the stackinfo structure.
* adds the runops_wrap() wrapper

It also adds rpp_obliterate_stack_to() for clearing the stack on
exceptions

Collectively, this allows each stack to be in one of three states:

1) AvREAL(PL_curstack) && PL_curstackinfo->si_stack_nonrc_base == 0

(the new default) all the SVs pointed to from the stack are
reference-counted.

2) AvREAL(PL_curstack) && PL_curstackinfo->si_stack_nonrc_base > 0

items on the stack are reference-counted only below si_stack_nonrc_base.

3) !AvREAL(PL_curstack)

(existing behaviour) no items on the stack are reference-counted.

The way it generally works is that runops loops assume that all the PP
functions they call out to are reference-count-aware. Where this isn't
yet the case, the recently-added pp_wrap() and xs_wrap() functions
assume a reference-counted stack, but use the si_stack_nonrc_base
mechanism to call out to PP or XS functions which aren't aware of a
reference-counted stack.

Conversely, the runops_wrap() function added by this commit wraps calls
to runops loops, since such loops work only with an RC stack. So if
called with a non-RC or partially-RC stack, the wrapper temporarily
fixes up the stack to be fully-RC, calls the real runops loop, then on
return reverts the stack back to it's non-RC ways, mortalising any
return values if necessary.

This downgrading and upgrading by pp_wrap()/xs_wrap() and
runops_wrap() allows handling of multiple nesting of when, for
example, perl calls pp_entersub(), which calls XS code, which calls
call_sv(), which calls a runops loop, which calls pp_entersub(), which
calls XS code, and so on.

For si_stack_nonrc_base, this index value marks the lowest position on
the argument stack which is not reference-counted. The special (and
normal) value of 0 indicates that *all* items on the stack are
reference-counted.

The new function rpp_obliterate_stack_to() is a bit like
rpp_popfree_to(), except that it can handle stacks in all three of the
states listed above. It's intended to be used when dying, throwing
exceptions or exiting, since the stack could be in any state when that
happens.

Note that as of this commit, PERL_XXX_TMP_NORC is still defined, which
means that even in the presence of AvREAL(PL_curstack) etc, the stack
isn't yet actually reference counted. So with this commit, perl goes
through all the motions, (calling wrappers like runops_wrap()
etc), but skips actually manipulating any reference counts. There will
be a few more commits, fixing up a few more things, before
PERL_XXX_TMP_NORC will be removed.


  Commit: 51c1aff3100b5a0fedb25ae0dd6add5b2e4914df
      https://github.com/Perl/perl5/commit/51c1aff3100b5a0fedb25ae0dd6add5b2e4914df
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  add stack extend to Perl_die_unwind()

When invoked via a scalar-context eval, die_unwind() was pushing
&PL_sv_undef without extending the stack first. It's been this way for
many years. Spotted by visual inspection while adding rpp_() code.

I could get a SEGV with the following code, but I haven't added it as a
test as it's highly sensitive to exactly what size stack is initially
allocated and the OS's malloc().

    my $x;
    my @a =
        ($x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         $x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,$x,
         scalar eval { die },
    );


  Commit: 6423f819d5a0a4768aa0758e11ea4dc555734966
      https://github.com/Perl/perl5/commit/6423f819d5a0a4768aa0758e11ea4dc555734966
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M toke.c

  Log Message:
  -----------
  make RC-stack-aware: Perl_filter_read()

This function in toke.c calls out to a random C-level filter function
for each source input chunk. Because that function may in turn invoke
a Perl function via call_sv() -  and may itself push stuff onto or off the
stack for that call -  present that function with a
non-reference-counted stack environment for backwards compatibility.


  Commit: 02ee8d3f05c12fab1f62db8b1738f12009b1fbf0
      https://github.com/Perl/perl5/commit/02ee8d3f05c12fab1f62db8b1738f12009b1fbf0
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M inline.h

  Log Message:
  -----------
  rpp_is_lone(): allow non-temp SV too

This function indicates whether an SV on the stack is kept alive only by
a single ref from the temps stack - which is often the case with stuff
pushed onto the stack by PP functions. Often this means that the SV can
be passed through rather then copied in places like returning from a
subroutine.

With a ref-counted stack, it's possible for a *non* SvTEMP SV to also be
stealable, if it has a refcount of 1, since that SV is being kept alive
purely by its (now refcounted) link from the stack.

So this commit adds that condition too (and also simplifies the
condition for efficiency).

In summary: originally perl (and then this function) did:

    if (SvTEMP(sv) && SvREFCNT(sv) == 1) { ... steal it ... }

Now this function's condition is the equivalent of

    #ifdef PERL_RC_STACK
        (    (SvREFCNT(sv) == 1)
        || (SvTEMP(sv) && SvREFCNT(sv) == 2))
    #else
        (SvTEMP(sv) && SvREFCNT(sv) == 1)
    #endif


  Commit: 602b5576796a0c058e07316af88ffc5d9a4e16dc
      https://github.com/Perl/perl5/commit/602b5576796a0c058e07316af88ffc5d9a4e16dc
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M deb.c
    M embed.fnc
    M embed.h
    M proto.h

  Log Message:
  -----------
  Perl_debstack(): indicate stack refcount status

When displaying the stack with perl -Ds or -Dsv, put a vertical bar (|)
at the boundary between the reference-counted part of the stack and the
non-reference-counted part, if any.

In addition with -Dsv, for each stack show its status;

    (real)         all items on the stack are reference-counted
    (partial real) items below si->si_stack_nonrc_base are RCed
    blank          no items are RCed

This commit switches to invoking S_deb_stack_n() directly, rather than
via the deb_stack_n() macro, as some compilers can't cope with the
'ifdef' amongst the calling args.


  Commit: 2efe8c4f2b9663fcc8e22a5a6c91155b336cb6cf
      https://github.com/Perl/perl5/commit/2efe8c4f2b9663fcc8e22a5a6c91155b336cb6cf
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M perl.h

  Log Message:
  -----------
  disable PERL_XXX_TMP_NORC

This macro was just a temporary crutch that disabled actually adjusting
the reference count of things being pushed and popped off the stack,
even on PERL_RC_STACK builds. It allowed the core to be converted to
support a reference-counted stack as a bunch of incremental changes.

This commit turns it off, enabling the stack to become actually
reference-counted on PERL_RC_STACK builds.

In a few commits' time, this macro will be completely eliminated from
the source code.


  Commit: 211db5f05d1253ed52f855aeae8cc7c80263224e
      https://github.com/Perl/perl5/commit/211db5f05d1253ed52f855aeae8cc7c80263224e
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M inline.h
    M pp.h

  Log Message:
  -----------
  stack push/pops: assert rpp_stack_is_rc() state

On perls built with both -DPERL_RC_STACK and -DDEBUG_LEAKING_SCALARS,
add asserts to the various old-style PUSHs() etc macros and new-style
rpp_push_1() etc functions that they're operating on the right sort of
stack. In particular:

PUSHs() and POPs() should only be used on stacks where rpp_stack_is_rc()
is false, since they don't modify the reference count of the SVs they
are pushing or popping.

Conversely, rpp_push_1(), rpp_popfree_1() etc should only be used on
stacks where rpp_stack_is_rc() is true, since they modify the reference
counts of the SVs they push and pop.

On perls not compiled with PERL_RC_STACK, the rpp_ functions don't
modify the reference counts, but on such builds the rpp_stack_is_rc()
assertions in the rpp_ functions are disabled, so it all works out
still.


  Commit: 9b88e00729e918eb28f249288bdc15087a256608
      https://github.com/Perl/perl5/commit/9b88e00729e918eb28f249288bdc15087a256608
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M dump.c

  Log Message:
  -----------
  runops_debug(): add RC-stack assertions

on PERL_RC_STACK builds,
1) assert that the stack is reference-counted (rpp_stack_is_rc()).
2) assert the any split point (si_stack_nonrc_base) isn't above the
    top of the stack.


  Commit: f17098b9a9ea813528d79ec9d36dc4b6ec2e4972
      https://github.com/Perl/perl5/commit/f17098b9a9ea813528d79ec9d36dc4b6ec2e4972
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_hot.c

  Log Message:
  -----------
  pp_wrap(), xs_wrap(): extract some common code

and put it in a static function, S_pp_xs_wrap_return().


  Commit: c3d9f945f728d5d5788a0c83c13cdfe5172d1a6e
      https://github.com/Perl/perl5/commit/c3d9f945f728d5d5788a0c83c13cdfe5172d1a6e
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_hot.c

  Log Message:
  -----------
  tweak pp_wrap() and xs_wrap()

After bumping up the reference counts of the returned values,
reset si_stack_nonrc_base earlier, so that if perl dies while
decrementing the original args, all reference counts will be properly
accounted for.

Also in xs_wrap(), only bother doing

    PL_markstack_ptr[0]  += nargs;

in the branch where nargs > 0.


  Commit: 6ff93f8cf249169fa14453a720bc32b27ffb0e86
      https://github.com/Perl/perl5/commit/6ff93f8cf249169fa14453a720bc32b27ffb0e86
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M MANIFEST
    M ext/XS-APItest/APItest.xs
    A ext/XS-APItest/t/xsppwrap.t

  Log Message:
  -----------
  add tests for XSPP_wrapped() macro

This new macro allows an old-style non-reference-counted PP-style
function to be used on a PERL_RC_STACK builds. It's intended for
non-core PP functions which are typically in an XS file and are used to
replace the PP function of an existing op, or to be attached to a custom
op.

It's virtually identical to the PP_wrapped() macro, except that it
uses the name as-is rather than prepending Perl_ to the name


  Commit: 87eac0e484cbf4c326f9324b19a5baf4ead0fcad
      https://github.com/Perl/perl5/commit/87eac0e484cbf4c326f9324b19a5baf4ead0fcad
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M ext/XS-APItest/APItest.xs

  Log Message:
  -----------
  XS::APItest::clone_with_stack(); check SI RC state

In this test function, push a couple of stackinfos, one with a
ref-counted stack, and one without.
After cloning, pop the cloned stackinfos and assert that the cloned
argument stacks are also appropriately RC or non-RC.

This should probably have been done properly as some new tests rather
than a couple of asserts, but that would have involved a lot more
effort.


  Commit: d65a66b37c26d2e54a15df1b902d8ed319e02c1a
      https://github.com/Perl/perl5/commit/d65a66b37c26d2e54a15df1b902d8ed319e02c1a
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M dist/threads/threads.xs
    M ext/XS-APItest/t/magic.t
    M inline.h
    M op.c
    M perl.c
    M perl.h
    M pp_ctl.c
    M pp_hot.c
    M pp_pack.c
    M pp_sort.c
    M run.c
    M t/cmd/for.t
    M universal.c

  Log Message:
  -----------
  Eliminate PERL_XXX_TMP_NORC

This macro was disabled a few commits ago. Now remove all use of it
from the core.

It was just a temporary crutch that disabled actually adjusting the
reference count of things being pushed and popped off the stack, even on
PERL_RC_STACK builds. It allowed the core to be converted to support a
reference-counted stack as a bunch of incremental changes.


  Commit: c9b45f429b51dba470aed40410d9a17f200d54b5
      https://github.com/Perl/perl5/commit/c9b45f429b51dba470aed40410d9a17f200d54b5
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pod/perlguts.pod

  Log Message:
  -----------
  add perlguts section on a reference-counted stack

Explain what all the new rpp_foo() functions are for.


  Commit: ae41033c73ec2f9d6d46bd40baacb45ea1a99207
      https://github.com/Perl/perl5/commit/ae41033c73ec2f9d6d46bd40baacb45ea1a99207
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M pp_ctl.c

  Log Message:
  -----------
  pp_goto: fix macro-in-macro compile error

Turns out MSVC 1.42 doesn't like

        FOO(bar,
    #ifdef X
            1
    #else
            0
    #endif
        );

where FOO is a macro.


  Commit: dec99a6d0e0299814863ac71ad7e258d9210bd46
      https://github.com/Perl/perl5/commit/dec99a6d0e0299814863ac71ad7e258d9210bd46
  Author: David Mitchell <davem@iabyn.com>
  Date:   2023-03-12 (Sun, 12 Mar 2023)

  Changed paths:
    M run.c
    M t/op/grep.t

  Log Message:
  -----------
  Perl_runops_wrap((): don't mortalise NULLs

This function was doing a delayed ref count decrement of all the SVs it
had previously temporarily incremented, by mortalising each one. For
efficiency it was just doing a Copy() of a block of SVs addresses from
the argument stack to the TEMPs stack.

However, the TEMPs stack can't cope with NULL pointers, while there are
sometimes NULL pointers on the argument stack - in particular, while
doing a map, any temporary holes in the stack are set to NULL on
PERL_RC_STACK builds.

The fix is simple - copy individual non-NULL addresses to the TEMPS
stack rather than doing a block copy.


Compare: https://github.com/Perl/perl5/compare/b7ef172541c9...dec99a6d0e02



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