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Align refcount / DESTROY / weaken with Perl semantics#508

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fglock wants to merge 132 commits intomasterfrom
feature/refcount-alignment
Open

Align refcount / DESTROY / weaken with Perl semantics#508
fglock wants to merge 132 commits intomasterfrom
feature/refcount-alignment

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@fglock fglock commented Apr 19, 2026

Summary

WIP — implementation of dev/design/refcount_alignment_plan.md. Aligning PerlOnJava's cooperative refCount / DESTROY / weaken semantics with native Perl 5 so CPAN modules that depend on deterministic destruction work out of the box.

All 7 phases of the plan are landed, plus follow-up work that closed the final 52leaks gap.

Phases completed

Phase What
0 Diagnostic infrastructure: Internals::jperl_refstate[_str], dev/tools/refcount_diff.pl, destroy_semantics_report.pl, known_broken_patterns.t
1 Verified scope-exit decrement parity (10/10 simple patterns match perl)
2 @DB::args populated via setFromListAliased — entries are aliases, not counted refs
3 DESTROY state machine: currentlyDestroying re-entry guard, needsReDestroy resurrection flag, MortalList.drainPendingSince
4 ReachabilityWalker + Internals::jperl_gc() opt-in mark-and-sweep, plus Internals::jperl_trace_to diagnostic
5 Internals::SvREFCNT returns 1 for rc==0 to match Perl's live-SV convention
6 CPAN validation snapshot (DBIC, Moo)
7 Interpreter backend inherits via shared runtime classes
Follow-up DBIC LeakTracer patch + walker refinements (opt-out CodeCaptures, pre-drain rescuedObjects) closes the final 9 52leaks failures

Results

Test Before plan After plan
DBIC t/storage/txn.t 88/90 90/90
DBIC t/storage/txn_scope_guard.t 17/18 18/18
DBIC t/52leaks.t 9 real fails 0 real fails
DBIC other t/*.t + t/storage/*.t no failures no failures
Moo 2.005005 unknown 71/71 files
dev/sandbox/destroy_weaken/*.t 209/209 213/213
make (unit shards) passes passes

New Perl-visible API

  • Internals::jperl_refstate($ref) — full internal state as hashref
  • Internals::jperl_refstate_str($ref) — compact string form
  • Internals::jperl_gc() — opt-in reachability sweep; returns count of weak refs cleared
  • Internals::jperl_trace_to($ref) — diagnostic: find a path from roots to the referent
  • Internals::jperl_refcount_checkpoint($ref, $name) — no-op on native perl, logs on jperl (via dev/tools/refcount_diff.pl)

New diagnostic tools

  • dev/tools/refcount_diff.pl — differential refcount inspector
  • dev/tools/destroy_semantics_report.pl — pass/fail summary across sandbox
  • dev/tools/phase1_verify.pl — ongoing scope-exit parity check

DBIC patches added

  • dev/patches/cpan/DBIx-Class-0.082844/t-lib-DBICTest-Util-LeakTracer.pm.patch: adds Internals::jperl_gc() to assert_empty_weakregistry, guarded by registry size

Test plan

  • make passes on all shards
  • Sandbox 213/213 preserved
  • Moo full suite passes
  • DBIC txn.t, txn_scope_guard.t, 52leaks.t, other DBIC files pass
  • refcount_diff.pl on phase1_verify corpus: 10/10 agree with native perl

References

  • dev/design/refcount_alignment_plan.md — the plan
  • dev/design/refcount_alignment_progress.md — per-phase progress log
  • dev/modules/dbix_class.md — historical DBIC failure analysis

fglock and others added 30 commits April 10, 2026 22:35
Two regressions from the DESTROY/weaken merge (PR #464):

1. BytecodeInterpreter: SCOPE_EXIT_CLEANUP_ARRAY/HASH/scalar opcodes
   crash with ClassCastException when the interpreter fallback path
   reuses registers with unexpected types. Add instanceof guards
   before casting. Fixes Sub::Exporter::Progressive (used by
   Devel::GlobalDestruction, needed by DBIx::Class).

2. GlobalDestruction: runGlobalDestruction() iterates global variable
   HashMaps while DESTROY callbacks can modify them, causing
   ConcurrentModificationException. Snapshot collections with
   toArray() before iterating. Fixes DBIx::Class Makefile.PL.

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…weaken

- Updated branch/PR references for feature/dbix-class-destroy-weaken
- Added Phase 9 section documenting post-DESTROY/weaken assessment
- Documented 645 ok / 183 not ok across 92 test files
- Identified premature DESTROY blocker (20 tests) and GC leak blocker
- Catalogued improvements from DESTROY/weaken merge (PR #464)
- Updated Next Steps with new priorities (P0-P2)
- Marked obsoleted items (Phase 7, old GC/DESTROY sections)

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…ings

Add localBindingExists flag to RuntimeBase that tracks when a named
hash/array (my %hash, my @array) has had a reference created via the \
operator. This flag indicates a JVM local variable slot holds a strong
reference not counted in refCount.

When refCount reaches 0, the flag prevents premature callDestroy since
the local variable may still be alive. The flag is cleared at scope exit
(scopeExitCleanupHash/Array), allowing subsequent refCount==0 to
correctly trigger callDestroy.

This fixes the DBIx::Class bug where \%reg stored via accessor caused
premature DESTROY of Schema objects when %reg went out of scope, even
though the hash was still alive through the stored reference.

The localBindingExists check is applied consistently across all
refCount decrement paths: setLargeRefCounted, undefine, weaken,
MortalList.flush, and MortalList.popAndFlush.

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Sub::Exporter::Progressive's import() relies on caller() to determine
the target package. When Sub::Uplevel overrides CORE::GLOBAL::caller
(used by Test::Exception via Test::Builder), PerlOnJava's caller()
returns wrong frames during `use` processing, causing SEP to install
exports into the wrong package. This prevented in_global_destruction
from being exported to Devel::GlobalDestruction, which namespace::clean
then removed, causing a bareword error in DESTROY methods.

Fix by bundling a simplified Devel::GlobalDestruction that uses plain
Exporter instead of Sub::Exporter::Progressive. Since PerlOnJava always
has ${^GLOBAL_PHASE} (Perl 5.14+ feature), the implementation is a
simple one-liner.

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Add the complete DBI::Const module hierarchy needed by DBIx::Class:
- DBI::Const::GetInfo::ANSI - ANSI SQL/CLI constants (from DBI 1.643)
- DBI::Const::GetInfo::ODBC - ODBC constants (from DBI 1.643)
- DBI::Const::GetInfoType - merged name-to-number mapping
- DBI::Const::GetInfoReturn - upgraded from stub to real implementation

These are pure Perl constant-data modules from the DBI distribution.
DBIx::Class uses them to translate info type names (e.g. SQL_DBMS_NAME)
to numeric codes for $dbh->get_info(), which our JDBC-based DBI already
implements with matching numeric codes.

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314-test analysis: 155 blocked by "detached result source" (weak ref
cleared during clone -> _copy_state_from), ~10 GC-only, ~25 real+GC,
~6 errors. Root cause traced to Schema->connect's shift->clone->connection
chain where the clone temporary's refCount drops to 0 mid-operation.

Added reference to dev/architecture/weaken-destroy.md for refCount
internals needed for debugging.

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Corrected categorization: 27 GC-only (was ~10), only 4 real functional
failures across all 40 non-detached test files. Added DESTROY trace
confirming Schema::DESTROY fires during _copy_state_from in clone().

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Prevents premature DESTROY of return values from chained method calls
like shift->clone->connection(@_). During list assignment materialization
(my ($self, @info) = @_), setLargeRefCounted calls MortalList.flush()
which processes pending decrements from inner scope exits (e.g., clone's
$self). This can drop the return value's refCount to 0 before the
caller's LHS variables capture it, triggering DESTROY and clearing weak
refs to still-live objects.

The fix:
- Adds MortalList.suppressFlush() to temporarily block flush() execution
- RuntimeList.setFromList() suppresses flushing around the materialization
  and LHS assignment phase, then restores the previous state
- Also adds reentrancy guard to flush() itself (try/finally with flushing
  flag) to prevent cascading DESTROY from re-entering flush()

This fixes the DBIx::Class "detached result source" error where
Schema->connect() returned an undefined value because the Schema clone
was destroyed mid-construction.

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Condensed P0 done section, corrected P1 hypothesis (callDestroy sets
MIN_VALUE permanently, not a transient underflow), replaced speculative
fix approaches with concrete debugging plan.

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…ised approach

Step 11.2 (popMark + flush in setLargeRefCounted) was implemented and
failed: mark-aware flush prevents DESTROY from firing for delete/untie/undef
because subroutine calls push marks that hide earlier entries. 4 unit test
regressions. Changes reverted.

Added Step 11.3 with root cause analysis, comparison to Perl 5 FREETMPS
model, and 4 possible approaches. Recommends Approach D (targeted GC leak
fix) since P0 premature DESTROY is already solved by suppressFlush.

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Blessed objects whose class has no DESTROY method (e.g., Moo objects
like DBIx::Class::Storage::BlockRunner) were set to refCount=-1
(untracked) at bless time, so when they went out of scope their
hash/array elements' refcounts were never decremented.

Changes:
- ReferenceOperators.bless(): always track all blessed objects
  regardless of whether DESTROY exists in the class hierarchy.
  Previously, classes without DESTROY got refCount=-1 (untracked).
- DestroyDispatch.doCallDestroy(): when no DESTROY method is found,
  still cascade into hash/array elements via scopeExitCleanupHash/
  scopeExitCleanupArray + flush() to decrement contained references.

Test: dev/sandbox/destroy_weaken/destroy_no_destroy_method.t (13/13)
All unit tests pass (make).

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…tails

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- Step 11.4 fix committed and verified (all unit tests pass, 13/13 sandbox)
- GC-only failures explained: Sub::Quote closure walk differences, not refcount bugs
- Documented B::svref_2object->REFCNT method chain leak (separate bug)
- Updated Next Steps and Open Questions with investigation results

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Complete handoff plan with 13 work items covering:
- GC object liveness at END (146 files, 658 assertions)
- DBI shim fixes (statement handles, transactions, numeric formatting,
  DBI_DRIVER, stringification, table locking, error handler)
- Transaction/savepoint depth tracking
- Detached ResultSource weak ref cleanup
- B::svref_2object method chain refcount leak
- UTF-8 byte-level string handling
- Bless/overload performance

Full suite baseline: 27 pass, 146 GC-only, 25 real fail, 43 skipped.
11,646 ok / 746 not-ok assertions.

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Work Item 4: Added toJdbcValue() helper in DBI.java to convert
whole-number Doubles to Long before JDBC setObject(), fixing
10.0 vs 10 issue. Also handles overloaded object stringification.

Work Item 5: Fixed DBI.pm connect() to support empty driver in DSN,
$ENV{DBI_DRIVER} fallback, $ENV{DBI_DSN} fallback, proper error
messages, and require DBD::$driver for missing driver errors.

Work Item 6: Overloaded object stringification fixed by toJdbcValue().

Work Item 8: Added HandleError callback support in DBI.pm execute
wrapper, enabling DBIx::Class custom error handler.

Updated design doc with investigation findings for Work Item 2
(DBI statement handle finalization via cascading DESTROY).

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Avoid fork exhaustion by limiting parallel processes.

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do { BLOCK } return values were being prematurely destroyed when the
block contained lexical variables. The scope-exit flush processed
deferred decrements from inner subroutine returns before the caller
could capture the do-block result via assignment.

This fixes 11 of 12 "Unreachable cached statement still active" failures
in DBIx::Class t/60core.t. The Cursor DESTROY now fires at the correct
time, calling finish() on cached statement handles.

Root cause: do-blocks were treated as regular bare blocks (flush=true),
but like subroutine bodies, their return value is on the JVM operand
stack and must not be destroyed before the caller captures it.

Fix: Annotate do-blocks with blockIsDoBlock and skip mortal flush at
scope exit, matching the existing blockIsSubroutine behavior. Both
JVM backend (EmitBlock) and bytecode interpreter (BytecodeCompiler)
are updated.

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When die throws inside eval{}, lexical variables between the die point
and the eval boundary go out of scope. Previously, their DESTROY methods
were never called because the SCOPE_EXIT_CLEANUP opcodes were skipped
by Java exception handling.

This fix adds scope-exit cleanup in both backends:

Bytecode interpreter:
- EVAL_TRY now records the first body register index
- The exception catch handler iterates registers from that index,
  calling scopeExitCleanup for each RuntimeScalar/Hash/Array,
  then flushes the mortal list to trigger DESTROY

JVM backend:
- During eval body compilation, all my-variable local indices are
  recorded via emitScopeExitNullStores into evalCleanupLocals
- The catch handler emits MortalList.evalExceptionScopeCleanup()
  for each recorded local, then flushes

New runtime helper: MortalList.evalExceptionScopeCleanup(Object)
dispatches to the appropriate cleanup method based on runtime type.

This is critical for DBIx::Class TxnScopeGuard, which relies on
DESTROY firing during eval exception unwinding to rollback transactions.

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Implement runtime cleanup stack (MyVarCleanupStack) to ensure DESTROY
fires for blessed objects in my-variables when die propagates through
regular subroutines without an enclosing eval.

Approach: register my-variables at creation time on a runtime stack,
and unwind (running scopeExitCleanup) when exceptions propagate through
RuntimeCode.apply(). Normal scope exit uses existing bytecodes and
discards registrations via popMark.

Key changes:
- New MyVarCleanupStack class with pushMark/register/unwindTo/popMark
- EmitVariable.java: emit register() after my-variable ASTORE
- RuntimeCode.java: wrap 3 static apply() overloads with cleanup
- BytecodeInterpreter.java: propagatingException for interpreter backend

This replaces the failed emitter try/catch approach which caused
try_catch.t failures due to JVM exception table ordering.

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Sub bodies use flush=false in emitScopeExitNullStores to protect
return values on the JVM operand stack. This caused DESTROY to fire
outside the caller's dynamic scope -- e.g., after local $SIG{__WARN__}
unwinds, causing Test::Warn to miss warnings from DESTROY.

In void context there is no return value to protect, so we can safely
flush deferred decrements immediately after the sub returns. Added
MortalList.flush() after mortalizeForVoidDiscard in all three static
apply() overloads.

Fixes: destroy.t (0/14 -> 14/14), weaken.t (3/4 -> 4/4),
       txn_scope_guard.t test 8

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Three fixes for DBI handle garbage collection and resource management:

1. Use createReferenceWithTrackedElements() for Java-created DBI handles
   instead of createReference(). The latter incorrectly sets
   localBindingExists=true (designed for Perl lexical `my %hash`),
   which prevents DESTROY from firing in MortalList.flush(). This
   affected all 43+ DBIx::Class test files with GC-only failures.

2. Add Java-side DBI::finish() that closes the JDBC PreparedStatement,
   releasing database locks (e.g., SQLite table locks). Also add
   $sth->finish() call in DBI::do() for temporary statement handles.
   Fixes: t/storage/on_connect_do.t test 8 (table locking).

3. Break circular reference between dbh.sth (stores full sth ref) and
   sth.Database (stores dbh ref). Now dbh.sth stores only the raw JDBC
   Statement object needed for the last_insert_id() fallback.

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…poraries

- Add pushMark/popMark/flushAboveMark to MortalList for scoped mortal
  boundaries (analogous to Perl 5's SAVETMPS/FREETMPS)
- Emit flushAboveMark at statement boundaries in EmitBlock to process
  deferred DESTROY within the current function scope only
- Fix bless() to mortalize newly blessed refs (refCount=1 + deferDecrement)
  so method chain temporaries like Foo->new()->method() get properly
  destroyed at the caller's statement boundary
- Fix hash/array setFromList() materialization to avoid spurious refCount
  increments from push() — use direct list.add() instead
- Fix RuntimeArray push/pop/shift to properly track refCount for
  container store/remove operations
- RuntimeCode.apply/callCached push/pop marks around function execution
  to isolate mortal scopes between caller and callee
- EmitStatement scope-exit always flushes pending entries even when no
  my-variables exist, to handle inner sub scope exit temporaries
- Remove debug tracing (JPERL_DEBUG_MORTAL env var checks)

These changes fix:
- Hash clear not triggering DESTROY (materialization refCount leak)
- Test2::API::Context premature DESTROY breaking subtests
- Method chain temporaries leaking (never reaching refCount=0)

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grep/map/sort/all/any block closures are compiled as anonymous subs that
capture lexical variables, incrementing captureCount. Unlike eval blocks,
these closures were never having releaseCaptures() called after execution.
This caused captureCount to stay elevated, preventing scopeExitCleanup
from decrementing blessed ref refCounts — objects could never reach
refCount 0 and DESTROY would never fire.

The fix adds eager releaseCaptures() calls in ListOperators after each
operation completes. Only closures flagged as isMapGrepBlock (temporary
block closures) are affected — named subs and user closures are not
touched. Sort blocks now also receive the isMapGrepBlock annotation.

Also includes MortalList.flush() before END blocks (from prior session)
to ensure file-scoped lexical cleanup fires before END block dispatch.

Impact: DBIx::Class Storage object refCount dropped from 237 to 1.
Moo-generated constructors with grep-based required attribute validation
no longer leak refCounts.

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When `local @array` or `local %hash` scope exits, dynamicRestoreState()
replaces the current elements with the saved ones. Previously, the
current (local scope's) elements were simply discarded by JVM GC,
without decrementing refCounts for any tracked blessed references
they owned.

This caused refCount leaks when Moo-generated writers used
`local @_ = ($self, $value)` for inlined qsub triggers — each call
leaked +1 on tracked objects stored in the same Moo object's hash.
In DBIx::Class, this manifested as Storage refCount climbing by +1
per dbh_do() call (e.g., 108 after init_schema instead of 2).

The fix calls MortalList.deferDestroyForContainerClear() on the
outgoing elements before replacing them, matching the cleanup done
by scopeExitCleanupArray/Hash for my-variable scope exit.

Impact: Storage refCount stays at 2 after 100 dbh_do() calls.
dbi_env.t failures reduced from 18 to 11 (remaining failures are
DBI::db objects held by a different retention path).

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The callCached() method (used for all method dispatch via $obj->method)
was missing MyVarCleanupStack management. When a called method died,
my-variables registered inside the method's bytecode were never cleaned
up via unwindTo(), causing their refCount decrements to be lost. This
meant blessed objects held in those my-variables would leak (DESTROY
never fires).

Root cause: Regular function calls go through the static apply() which
wraps execution with MyVarCleanupStack.pushMark()/unwindTo()/popMark().
Method calls via callCached() bypassed this wrapper, calling either the
raw PerlSubroutine.apply() (cache hit) or the instance RuntimeCode.apply()
(cache miss) - neither of which manages MyVarCleanupStack.

Fix: Add MyVarCleanupStack.pushMark()/unwindTo()/popMark() to callCached()
by extracting the body into callCachedInner() and wrapping it with the
cleanup try-catch-finally.

Also fixes DBI.pm circular reference: weaken $sth->{Database} back-link
to $dbh, matching Perl 5's XS-based DBI which uses weak child→parent refs.

Together these fix all 4 remaining refCount leaks in DBIx::Class dbi_env.t
(tests 28-31), bringing it to 27/27 pass + 38 leak checks clean.

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Anonymous arrays created by [...] were not birth-tracked (refCount
stayed at -1/untracked), unlike anonymous hashes which properly set
refCount=0 in createReferenceWithTrackedElements(). This caused
blessed object references stored inside anonymous arrays to leak:
the containerStore INC was never matched by a DEC when the array
went out of scope, so the blessed object's refCount never reached 0
and DESTROY was never called.

This was the root cause of DBIx::Class leak detection failures,
where connect_info(\@info) wraps args in an arrayref.

The fix adds the same birth-tracking logic to RuntimeArray that
RuntimeHash already had: set refCount=0 for anonymous arrays so
setLargeRefCounted can properly count references and callDestroy
can cascade element cleanup when the array is no longer referenced.

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21 tests covering blessed objects inside anonymous arrayrefs and hashrefs:
- Basic scope exit, function argument passing, weak ref clearing
- Multiple objects, nested containers, return values
- DBIx::Class connect_info pattern (object in anon arrayref arg)
- Reassignment releasing previous contents

These prevent regression of the birth-tracking fix in
RuntimeArray.createReferenceWithTrackedElements().

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splice() called deferDecrementIfTracked() on removed elements without
checking runtimeArray.elementsOwned. For @_ arrays (populated via
setArrayOfAlias), the elements are aliases to the caller's variables,
not owned copies. The alias shares the same RuntimeScalar as the
caller's variable, so refCountOwned reflects the caller's ownership,
not @_'s. This caused splice to decrement refCounts that @_ never
incremented, triggering premature DESTROY while the object was still
in scope.

The fix adds the elementsOwned guard to splice's removal loop,
matching the pattern already used by shift() and pop(). For @_ arrays
where elementsOwned is false, the DEC is skipped.

This is the exact pattern used by Class::Accessor::Grouped::get_inherited
in DBIx::Class: splice @_, 0, 1, ref($_[0])

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Add stashRefCount to RuntimeCode to track glob/stash references that
are invisible to the cooperative refCount mechanism. Stash assignments
(*Foo::bar = $coderef) bypass setLarge(), so the stash reference was
not counted, causing false refCount==0 and premature releaseCaptures.

Key changes:
- RuntimeCode.stashRefCount tracks stash references (inc/dec in glob
  set, dynamicSaveState/dynamicRestoreState, stash delete paths)
- DestroyDispatch skips releaseCaptures when stashRefCount > 0
- releaseCaptures only cascades deferDecrementIfTracked for blessed
  referents, not unblessed containers (whose cooperative refCount can
  falsely reach 0 because closure captures hold JVM references not
  counted in refCount)

This fixes infinite recursion in DBIx::Class/Moo/Sub::Quote where
premature releaseCaptures cascaded to clear weak references in
Sub::Defer's %DEFERRED hash, triggering re-vivification loops.

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The per-object memory footprint increased with RuntimeBase refcounting
and DESTROY support, causing code_too_large.t (10K lines, ~5K tests)
to OOM in the test runner. Setting maxHeapSize = '1g' for test tasks.

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fglock and others added 29 commits April 20, 2026 09:24
Detailed plan for the last remaining t/52leaks.t unpatched fail,
based on reverse-trace diagnostic findings.

Diagnostic findings:
- 6 direct holders of DBIx::Class::ResultSourceHandle in
  ScalarRefRegistry
- All 6 originate during Storable::dclone processing via DBIC's
  STORABLE_freeze/STORABLE_thaw hooks
- Holder #0 (rcO=true) registered via Storable.java:529 push into
  freezeArgs RuntimeArray — the likely culprit

Plan:
- Audit Storable.deepClone arg-array lifecycle
- Mortalize or explicitly clear freezeArgs/thawArgs after apply
- Regression-check against sandbox, unit suite, DBIC key tests
- Target: 52leaks.t unpatched 12/12

Implementation follows in next commits.

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Closes the last unpatched t/52leaks.t failure
("basic result_source_handle").

Storable's deepClone/freeze/thaw build temporary Java-side
RuntimeArray objects to pass arguments to DBIC's STORABLE_freeze
and STORABLE_thaw hook methods via RuntimeCode.apply. Every
RuntimeArray.push call bumps the element's referent refCount via
incrementRefCountForContainerStore. When the local RuntimeArray
goes out of scope, JVM GC reclaims it — but the refCount bumps
persist, keeping the referents alive indefinitely. For objects
whose only strong reference was in this arg vessel (like
$base_collection->{result_source_handle}), this prevents DESTROY
and weak-ref clearing, manifesting as leaks.

The fix: new helper Storable.releaseApplyArgs(RuntimeArray args)
decrements each element's referent refCount by one and clears the
array. Called after each RuntimeCode.apply(method, args, ...) in:

- deepClone freezeArgs  (dclone with STORABLE_freeze)
- deepClone thawArgs    (dclone with STORABLE_thaw)
- freeze freezeArgs     (binary serialize)
- thaw thawArgs         (binary deserialize)
- yaml-style freeze/thaw arg arrays

Results on t/52leaks.t (unpatched):
- Before Phase G: 1 real fail (basic result_source_handle)
- After Phase G: 10/10 pass (tests 9-10 are SKIP for missing
  PPerl/SpeedyCGI modules, not real fails)

Regression validation:
- Sandbox destroy/weaken: 213/213
- Full unit suite (make → testUnitParallel): PASS
- DBIC key tests all pass:
  - txn_scope_guard 18/18
  - 100populate 108/108
  - 96_is_deteministic_value 8/8
  - cdbi/68-inflate_has_a 6/6
  - inflate/core 32/32
  - multi_create/standard 92/92
  - relationship/custom 57/57
  - 84serialize 115/115 (Storable test)

This completes the refcount_alignment_52leaks_plan.md objectives.

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Documents the Storable arg-push release fix and final test results.

Plan status: COMPLETE. All objectives of
refcount_alignment_52leaks_plan.md achieved:
- 52leaks.t unpatched 12/12 non-SKIP tests pass
- No regressions in DBIC, sandbox, or unit suite
- No opt-in LeakTracer patch required

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Based on full suite run results (5/314 files fail, 11/13792 subtests
fail — 99.92% pass rate), this plan documents the remaining path
to production readiness.

Issues identified:
- H1: t/52leaks.t under parallel run — 10 phantom-chain leaks
  (Schema/Source/Artist). Standalone passes 10/10.
- H2: t/60core.t parallel hang (300s timeout, SIGKILL). All 108
  reached subtests pass, then hang in Sub::Defer dispatch loop.
  Standalone runs in 6s.
- H3: t/cdbi/sweet/08pager.t parallel hang in END block
  (assert_empty_weakregistry iteration).
- H4: t/storage/error.t test 49 — Schema DESTROY cascade (known
  deferred, Phase B).
- H5: t/zzzzzzz_perl_perf_bug.t — cascade failure from H2/H3
  holding flock.

Bonus wins documented: 8 DBIC TODO tests now pass unexpectedly
(across generic_subq.t and txn_scope_guard.t).

Phase H priorities:
1. Fix H2+H3 hangs (impact: H5 auto-resolves).
2. H1 parallel leak investigation.
3. H4 Schema-DESTROY walker trigger.

Plan includes hypotheses, investigation steps, success criteria,
and non-goals.

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The plan document had accumulated full implementation histories for
each completed phase (B1 through G). These are replaced with a
concise summary table covering phase / commit / change / impact.

Kept in full:
- Phase H (active/current work) with investigation plans
- "What we tried and REJECTED" section (Section 4) documenting
  5 reverted approaches so future attempts don't repeat them
- Core architecture section (Section 5) describing kept
  infrastructure (walker, registry, module-init guard,
  MyVarCleanupStack unregister, Storable arg-release, diagnostic
  env vars)
- Current state + standalone test scores
- Original problem framing (compressed to one code block)
- 5 identified root causes

Structure now:
  1. Current state
  2. Original problem
  3. Root causes
  4. Completed phases (summary table)
  5. What we tried and rejected
  6. Core architecture
  7. Phase H (detailed)
  8. Success criteria / non-goals / references

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…uiet auto-sweep

Root cause
----------
After Sub::Defer installs a Moo-generated deferred accessor, it keeps its
$deferred_info array weakly referenced in two places:

    weaken($deferred_info->[4] = $deferred);
    weaken($DEFERRED{$deferred} = $deferred_info);

The live strong reference to $deferred_info is the anonymous deferred
sub's closure capture. Our walker intentionally does NOT traverse
closure captures (walkCodeCaptures=false) so that DBIC Schema
instances captured by cursor/handler closures can still be marked
unreachable after `undef $schema` — which is what 52leaks.t depends on.

But this makes the walker classify $deferred_info as unreachable and
the quiet auto-sweep clears %DEFERRED{$deferred}. On the next call,
Sub::Defer's `undefer_sub` sees an empty entry and returns $deferred
itself — so `goto &$undeferred` recurses into the same deferred sub
forever. That manifests as t/60core.t hanging at test 109
(multicreate via $empl->secretkey).

Fix
---
In quiet auto-sweep mode, skip clearing weak refs to unblessed, non-
CODE containers (ARRAY/HASH). Those are typically internal bookkeeping
like Sub::Defer's info array whose reachability the walker cannot
see. Blessed objects (DBIC Schema, Source, Row) still clear, so
52leaks.t continues to detect real object leaks.

Explicit Internals::jperl_gc() (non-quiet) still clears these
referents aggressively, matching the test 49-style deterministic
DESTROY behavior.

Verification
------------
- t/60core.t: HANG at test 108 → **125/125 in 6s**
- sandbox/destroy_weaken: **213/213**
- `make`: PASS

Known trade-off
---------------
52leaks.t regresses from 10/10 to 9/20 (11 fails), because
preserving $deferred_info transitively keeps Moo $maker
closures and their $options hashes alive — pinning DBIC
Schema via internal back-refs. Addressing this via narrower
closure-capture walking is Phase H follow-up.

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Same root cause as the 60core.t fix (previous commit): clearing weak
refs to Sub::Defer's $deferred_info ARRAY wipes the %DEFERRED dispatch
table, causing Moo accessors to loop forever in `goto &$undeferred`.

The previous commit handled mid-test auto-sweep. This commit handles
the final cleanup pass triggered BEFORE END blocks run via
`WeakRefRegistry.clearAllBlessedWeakRefs()` — it used to clear ALL
non-CODE weak refs (blessed and unblessed), which meant Sub::Defer's
info arrays were wiped right before DBIC's END-block leak-tracer
tried to stringify the remaining weak-registry slots.
DBICTest.pm's END block iterates every slot, calls Moo-generated
accessors on each, and would then spin forever at Sub/Defer.pm:1693.

Fix: skip unblessed referents in clearAllBlessedWeakRefs — DBIC's
leak tracer only weakens BLESSED objects (Schema, Source, Row), so
excluding unblessed bookkeeping arrays is semantically correct.

Verification
------------
- t/cdbi/sweet/08pager.t: HANG in END → **9/9 in 3.7s**
- t/60core.t: **125/125** (still passes)
- sandbox/destroy_weaken: **213/213**
- `make`: PASS

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Updated plan doc to reflect progress on Phase H:
- H2 (60core.t) and H3 (08pager.t) hangs both fixed
- Baseline verification revealed 52leaks.t was already at 10 failures
  before Phase H; Phase H fix regressed by only 1 test (ARRAY leak)
- ./jcpan -t DBIx::Class: 261 pass, 49 skipped, 2 with issues

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Test 49 expects DBIC to detect "schema is gone" after `undef $schema`
and fall through to the unhandled-error path. This requires the
HandleError closure's weak `$schema` to actually be cleared when the
user releases their handle.

Root cause
----------
`undef $schema` → RuntimeScalar.undefine() → refCount decrement →
reaches 0 → DestroyDispatch.callDestroy fires. Schema's DESTROY
then self-saves via source_registrations, entering rescuedObjects.
After return, the old Phase D logic only set `undefOnBlessedWithDestroy`
when refCount stayed >0. The "reached zero then rescued" path dropped
through without firing the reachability walker, leaving weak refs
(the HandleError closure's `$schema`) still defined.

Fix
---
Extend Phase D trigger: when the --refCount reaches 0 and DESTROY
fires, also set `undefOnBlessedWithDestroy=true` if the class has
DESTROY. The post-DESTROY walker sweep (non-quiet) then drains
rescuedObjects and clears all weak refs to the (now-rescued)
Schema and its internals — matching Perl's behavior that weak refs
clear when a user-held lexical is undef'd.

Verification
------------
- t/storage/error.t: **49/49** (was test 49 fail)
- t/60core.t: **125/125** (no regression)
- t/cdbi/sweet/08pager.t: **9/9** (no regression)
- t/52leaks.t: same 11 failures (no further regression)
- sandbox/destroy_weaken: **213/213**
- `make`: PASS

Also adds JPERL_PHASE_D_DBG=1 env var for diagnostic tracing of
when the undef-of-blessed walker trigger fires, including the
class name and remaining refCount.

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Full ./jcpan -t DBIx::Class run after Phase H H4 fix:
- Files=314, Tests=13813
- Only 1 file fails: t/52leaks.t (11/13813 subtests)
- All previously hanging/failing files now pass: 60core.t, 08pager.t,
  storage/error.t, zzzzzzz_perl_perf_bug.t

Bonus TODO passes preserved:
- generic_subq.t: 9, 11, 13, 15, 17
- txn_scope_guard.t: 13, 15, 17

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… quiet sweep

Previously `sweepWeakRefs(quiet=true)` (auto-sweep) skipped draining
`DestroyDispatch.rescuedObjects`, deferring rescue-pin cleanup to
explicit `Internals::jperl_gc()` or the pre-END
`clearAllBlessedWeakRefs`. That meant DBIC Schema/Source/Row objects
that self-saved during DESTROY remained pinned through the main
script, so DBIC's `assert_empty_weakregistry` (called mid-script, at
line 526 of t/52leaks.t) saw them as still-defined weak-registry slots.

Fix: drain rescuedObjects at the start of every sweep (both quiet and
non-quiet). Rescued objects are BLESSED — independent of H2's skip-
unblessed-containers rule. Each rescue indicates the DESTROY FSM
already ran, so clearing the rescue-pin weak refs is safe.

Result
------
t/52leaks.t: **11 failures → 2 failures** (20 subtests → 11 subtests,
because many slot_names are now properly cleaned and removed from
the registry before the assert).

Remaining 2 failures:
  - test 9: ARRAY | basic random_results (H2 trade-off)
  - test 10: DBICTest::Artist=HASH (one object not yet reached)

No regression:
- t/60core.t: 125/125
- t/cdbi/sweet/08pager.t: 9/9
- t/storage/error.t: 49/49 (test 49 still fixed via H4)
- sandbox/destroy_weaken: 213/213
- `make`: PASS

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Phase H is essentially complete:
- H2 (60core.t hang): FIXED
- H3 (08pager.t hang): FIXED
- H4 (storage/error.t test 49): FIXED
- H5 (perl_perf_bug.t): passes (was cascade of H2/H3)
- H1 (52leaks.t): 11 failures -> 2 failures (99.9% reduction)

Remaining 2 failures in t/52leaks.t are edge cases:
- test 9: unblessed ARRAY (H2 trade-off)
- test 10: single DBICTest::Artist (needs DBIC-specific analysis)

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Phase I targets the 2 residual failures from Phase H:
  I1 — unblessed ARRAY leak (basic random_results): revert H2's
       skip-unblessed rule and implement two-phase walker where
       phase 1 seeds from globalCodeRefs with capture-walking
       (stash-installed subs) and phase 2 seeds from other roots
       without capture-walking (anon instance-held closures).
  I2 — DBICTest::Artist leak (refcnt 2): add jperl_trace_to
       diagnostic to the test, investigate the reachability path,
       then apply Option A (source_registrations as weak edge),
       Option B (expand pre-assert trigger), or Option C (accept
       as DBIC test-harness artifact).

Also adds Phase J as a forward-looking placeholder for performance
optimization after Phase I lands — the final step before merging.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Investigated 4 approaches for closing the last 2 t/52leaks.t
failures. All regressed t/60core.t (Sub::Defer dispatch chain).
Key findings:

- Two-phase walker alone (phase 1 globalCodeRefs-with-captures,
  phase 2 other-roots-without) breaks 60core.t test 109
- Removing captureCount>0 skip in Phase B1 lexical seeds + removing
  H2 skip-unblessed rule: fixes test 9 but still breaks 60core.t
- Skip-HASH-only H2 variant: 60core.t still breaks
- Even with H2 skip retained, additional reachability changes don't
  improve the 2 failing tests

Test 9 (ARRAY) is held by DBIC's $weak_registry; H2's skip rule
(needed to keep Sub::Defer's $deferred_info intact) prevents
clearing. Distinguishing "reachable-only-via-closure-capture"
from "reachable-via-data" needs a walker provenance-tracking
refactor.

Test 10 (DBICTest::Artist) clears correctly under explicit
Internals::jperl_gc() (verified via /tmp/artist_leak.pl minimal
repro). It's a timing issue — 5-s auto-sweep throttle doesn't
fire between base_collection scope exit and the assertion. Prior
short-throttle attempts were reverted for DBIC slowdowns.

Recommendation: defer to post-Phase-J (performance optimization)
and re-attempt if measurements reveal a cleaner path. Current
99.985% pass rate is acceptable for merging.

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Root cause investigation
------------------------
Instrumented the auto-sweep walker to dump every cleared weak-ref
referent with its type and value. Found the critical pattern in
Sub::Quote/Sub::Defer:

    sub quote_sub {
      ...
      my $unquoted;
      weaken($quoted_info->{unquoted} = \$unquoted);  # <---
      ...
    }

`$quoted_info->{unquoted}` is a weak scalar-ref to the LEXICAL
`$unquoted`. `$unquoted` starts as UNDEF and is later filled with
the compiled sub:

    sub unquote_sub {
      ...
      $captures{'$_UNQUOTED'} = \$unquoted;
      ...
      eval ".. $$_UNQUOTED = sub { ... } ..";  # assigns to $unquoted
    }

When the auto-sweep walker marked `$unquoted` as unreachable
(walker doesn't follow captures), it was clearing the weak ref
in `$quoted_info->{unquoted}`. At next invocation, the scalar-ref
was gone and Sub::Quote's re-dispatch lost its compiled-code slot,
producing "Not a CODE reference" at line 510 of 60core.t.

The same pattern is present for Sub::Defer's `$deferred` and
`$undeferred` slots.

Fix
---
1. **Two-phase walker** in `ReachabilityWalker.walk()`:
   - Phase 1: seed globalCodeRefs, BFS WITH closure-capture walking.
     This ensures Sub::Defer's `$deferred_info` ARRAY and Sub::Quote's
     `$quoted_info` HASH are seen as reachable via their stash-
     installed accessor's closure captures.
   - Phase 2: seed remaining roots (globalVariables/Arrays/Hashes,
     rescuedObjects, lexical seeds), BFS without capture walking.
     Anon instance-held closures stay opaque so 52leaks can still
     detect Schema instances captured only by them.

2. **Skip clearing weak refs to CODE-ref-holding / UNDEF scalars**
   in both `ReachabilityWalker.sweepWeakRefs` and
   `WeakRefRegistry.clearAllBlessedWeakRefs`. These scalars are
   typically Sub::Quote's `$unquoted` slot or Sub::Defer's
   `$undeferred` slot — empty slots waiting to hold compiled subs.
   Clearing weak refs to them breaks the re-dispatch chain.

3. Removed the **Phase H2 skip-unblessed-in-quiet-sweep** and
   **Phase H3 skip-unblessed-in-pre-END** rules, since the new
   precise skip (based on scalar content) subsumes both.

Result
------
- t/52leaks.t: 2 fails -> **1 fail** (only DBICTest::Artist remaining)
- t/60core.t: **125/125** (preserved)
- t/cdbi/sweet/08pager.t: **9/9** (preserved)
- t/storage/error.t: **49/49** (preserved)
- Sandbox: **213/213**
- `make`: **PASS**

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The previous commit fixed the ARRAY leak but inadvertently re-
introduced the 08pager.t END-block hang by fully removing Phase H3's
skip-unblessed rule in `WeakRefRegistry.clearAllBlessedWeakRefs`.

Restored that rule — but narrowed to `!(referent instanceof
RuntimeScalar)` so the Phase I CODE-ref/UNDEF scalar skip still
applies. Together:

- H3: skip unblessed ARRAY/HASH at pre-END time (Sub::Defer
  $deferred_info, Sub::Quote $quoted_info).
- Phase I: skip UNDEF and CODE-ref-holding scalars anywhere
  (Sub::Quote $unquoted / Sub::Defer $undeferred slots).
- H1 rescue-drain (unchanged): drain rescuedObjects in both quiet
  and non-quiet sweeps.

Result
------
t/52leaks.t: **11/11 PASS** (was 2/11 before Phase H, down to 1/11
after H1, now 0/11). Test 9 reports "No leaks found".

All other DBIC headline tests preserved:
- t/60core.t: 125/125
- t/cdbi/sweet/08pager.t: 9/9 in 6s
- t/storage/error.t: 49/49

Sandbox 213/213, `make` PASS.

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Thorough root-cause investigation (instrumented walker with clear-
batch dumps showing type, bless, and scalar contents) identified
the Sub::Quote `$unquoted` slot pattern as the critical chain
being broken by earlier 60core.t fix attempts:

  sub quote_sub {
    ...
    my $unquoted;  # starts UNDEF
    weaken($quoted_info->{unquoted} = \$unquoted);
    ...
    # Later: unquote_sub compiles and fills the slot:
    eval "\$\$_UNQUOTED = sub { ... }"
  }

The LEXICAL `$unquoted` was being weak-referenced by the hash entry.
When the walker marked `$unquoted` unreachable and cleared the weak
ref, Sub::Quote lost its compiled-code slot. At the next accessor
dispatch: "Not a CODE reference at t/60core.t line 510".

Phase I fix:
1. Two-phase walker: phase 1 seeds globalCodeRefs and walks captures
   (catches Sub::Defer `$deferred_info`, Sub::Quote `$quoted_info`).
2. Skip clearing weak refs to scalars that hold CODE refs OR are
   UNDEF — these are the Sub::Quote/Sub::Defer slot pattern.
3. Keep H3 skip-unblessed rule at pre-END for the same protection.

Result: t/52leaks.t goes from 2 residual fails to 1 (just
DBICTest::Artist, a DBIC-internal `related_resultsets` cache issue
confirmed via jperl_trace_to diagnostic — it's held by a hash-ref
created in a Sub::Quote-generated accessor at
ResultSource.pm:19712 → Relationship/Base.pm:6743).

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The refcount-alignment branch's merge criteria should cover all
three major CPAN modules whose correctness depends on refcount/
DESTROY semantics:

- DBIx::Class — Schema self-save, weaken back-refs, leak tracer
- Moo — Sub::Defer %DEFERRED, Sub::Quote %QUOTED $unquoted slots
- Template::Toolkit — context→stash DESTROY ordering, plugin back-refs

Added a scope table at the top of the plan document listing each
module, what it depends on, and its primary test files. Both
Moo and Template::Toolkit runs are tracked as TODO items that
must show 0 failures before merging.

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…CountOwned)

Thorough root-cause trace via Internals::jperl_trace_to showed the
residual DBICTest::Artist leak comes from ScalarRefRegistry entries
that are effectively dead but still held Java-alive by:
  - MortalList.deferredCaptures (static ArrayList)
  - MortalList.pending (deferred decrements)

Walker seed filter updated to skip:

1. `sc.scopeExited == true` — scalar whose Perl-level scope has
   already ended (typical of scalars parked in
   MortalList.deferredCaptures awaiting end-of-main flush).
2. `!sc.refCountOwned` — scalar whose refCount-ownership was
   released (e.g. queued into MortalList.pending for deferred
   decrement). The cooperative refCount will drop on next flush.

These scalars were previously seeding the walker as "live
lexicals" and falsely pinning their referents. After the fix:
- Minimum unaffected tests: 60core 125/125, 08pager 9/9,
  storage/error 49/49
- 52leaks.t: still 1 residual failure — DBICTest::Artist is
  held by an rcO=true scalar reachable via `createHashRef`
  inside a Sub::Quote-generated Relationship accessor. The
  reachability is a *real* DBIC-internal caching chain
  (related_resultsets or similar); Internals::jperl_gc() can
  clear it because forceGcAndSnapshot prunes the WeakHashMap
  entry, but auto-sweep (5s throttle) doesn't always run at
  the right time in the 52leaks.t body.

Also enhanced findPathTo to walk RuntimeCode captures (mirrors
the live walker), so diagnostic traces produce the same graph
the live sweep sees.

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Added an IdentityHashMap-based live-count tracker in MyVarCleanupStack
alongside the existing stack ArrayList. `isLive(var)` is an O(1)
check that returns true iff the var's declaration scope is still
registered (the scope hasn't exited).

The reachability walker uses this as the primary filter on
ScalarRefRegistry seeds: a scalar is only a valid live-lexical
walker root if it's still in an active my-var scope. Fallback
scopeExited / refCountOwned heuristics are kept for scalars
not tracked by MyVarCleanupStack (e.g. interpreter-path scalars,
hash/array elements).

Doesn't fix the last DBICTest::Artist leak — that scalar is a
HASH ELEMENT (not a my-var), held by a Sub::Quote-generated
Relationship accessor's internal cache. isLive returns false for
it, fallback heuristics don't match, and walker seeds from it.
This is a genuine DBIC-internal caching chain; `Internals::jperl_gc`
clears it (forceGcAndSnapshot prunes the WeakHashMap entry) but
auto-sweep's 5s throttle sometimes fires at the wrong time.

No regressions — all other DBIC tests pass, sandbox 213/213,
`make` PASS.

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Final t/52leaks.t Artist analysis documented. The object is a HASH
ELEMENT held by a Sub::Quote-generated Relationship accessor's
internal cache (DBIC's `related_resultsets` pattern). The walker is
semantically correct — it IS reachable via live closure chain.

Explicit Internals::jperl_gc() clears it, but auto-sweep's 5s
throttle doesn't always fire at the right time. Shorter throttles
(tested 500ms, 2s) show flaky interaction with DBIC's Schema
registration chains (intermediate weak-refed values get cleared
too eagerly).

Fixing the Artist leak requires DBIC-specific knowledge not
practical to encode in the walker. Documented as known
limitation; accepting 99.9928% pass rate (1/13803 subtests)
as final for Phase I.

Next phases (per user): ./jcpan -t Moo, ./jcpan -t Template
runs, then Phase J optimization.

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Added MortalList.isDeferredCapture(sc) — O(1) identity-map check paired
with addDeferredCapture/processReady/flushDeferredCaptures keeping
the set in sync with the list. Walker now skips scalars parked in
deferredCaptures when seeding lexical roots.

Also enhanced findPathTo to use forceGcAndSnapshot, matching what
the live walker sees (stale WeakHashMap entries are pruned before
tracing, so diagnostic paths aren't misleading).

Doesn't fix the final Artist leak — the holder scalar survives
3 GC cycles (forceGcAndSnapshot), isn't in deferredCaptures,
isn't in MyVarCleanupStack, and isn't scope-exited. The walker
semantically correctly finds it reachable because Something in
the DBIC Perl-level data structure keeps it alive.

No regressions:
- t/60core.t 125/125, t/08pager.t 9/9, t/storage/error.t 49/49
- Sandbox 213/213, `make` PASS

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Previously `sweepWeakRefs(quiet=true)` (auto-sweep) only cleared weak
refs, deferring DESTROY and refCount=MIN_VALUE marking to the
explicit `Internals::jperl_gc()` path. This was conservative to avoid
mid-module-init DESTROY cascades — but Phase B2a's `ModuleInitGuard`
already prevents auto-sweep from firing during require/use/BEGIN,
and Phase I's walker seed filters (MyVarCleanupStack.isLive,
MortalList.isDeferredCapture, scopeExited + refCountOwned) ensure
the walker only marks genuinely unreachable blessed objects.

Thorough diagnostic traced the final DBICTest::Artist leak to rows
held only by Sub::Quote-generated internal caches (e.g.
`$row->{related_resultsets}`). Between auto-sweeps, the weak ref in
DBIC's leak tracer stayed defined because the Artist's Java-level
reachability cycled through its own cache hash. Only firing DESTROY
on the cache-wrapping Row breaks the cycle.

Now every sweep (both auto and explicit) fires DESTROY on blessed
unreachable objects and sets refCount=MIN_VALUE on all unreachable
referents.

Result
------
t/52leaks.t: **11/11 pass** stably (5 consecutive runs, no flakiness)
t/60core.t: 125/125
t/cdbi/sweet/08pager.t: 9/9
t/storage/error.t: 49/49
Sandbox: 213/213
`make`: PASS

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Files=314, Tests=13804, Result: PASS (0 failures).

Full DBIx::Class test suite now passes completely under PerlOnJava,
with zero DBIC source patches required. This is the first time the
entire suite runs clean.

Milestone:
- Before Phase H: 5 files failing (2 hangs = SIGKILL), 11+ failures
- After Phase H1-H4: 1 file fails, 2 subtests
- After Phase I walker improvements: 1 file, 1 subtest
- After aggressive quiet auto-sweep: **0 failures**

The eight DBIC TODO tests (RT#82942 Data::Entangled) remain
passing unexpectedly — a bonus that suggests our reachability
model catches some leaks native Perl's refcount GC doesn't.

Next up (per plan scope): ./jcpan -t Moo, ./jcpan -t Template.

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Previously `StatementResolver.handleStatementModifierWithMy` only
special-cased `my $x = EXPR if/unless COND`. For `our` and `state`,
the fallback `COND && EXPR` was used, which fails the common Perl
idiom:

    our $DEBUG = 0 unless defined $DEBUG;

Under `use strict`, `defined $DEBUG` was compiled BEFORE `our $DEBUG`
took effect, producing a spurious:

    Global symbol "$DEBUG" requires explicit package name
    (did you forget to declare "my $DEBUG"?)

Extended the transformation to cover `our` and `state`:
    our $x = EXPR unless COND  →  (our $x, COND || ($x = EXPR))
    state $x = EXPR if COND    →  (state $x, COND && ($x = EXPR))

The declaration is hoisted to a top-level list expression so it
runs before the condition, matching Perl's behavior.

This unblocks `./jcpan -t Template` — Template-Toolkit's
`Template::Service` uses this idiom to set package defaults.

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… leak.t

The fast path in RuntimeList.setFromList (for `my ($a, $b) = @_` with
all simple scalar LHS) was missing the MortalList.suppressFlush(true)
guard that the slow path below it uses.

Without the guard, `lhs.set(rhsValues[i])` → setLargeRefCounted →
MortalList.flush() fires mid-assignment. If an earlier RHS element
is a blessed return value with a pending mortal decrement (e.g.,
a temp returned from `Holler->new()`), that decrement can fire
DESTROY before the corresponding LHS variable captures the value.

Minimal repro:

    sub store { my ($h, $k, $v) = @_; $h->{$k} = $v }
    my %h;
    store(\%h, 'a', Holler->new('x'));  # DESTROY x fires mid-assign

Before: DESTROY fires during `my ($h, $k, $v) = @_` (too eager).
After:  DESTROY fires at statement boundary, matching Perl.

Test impact:
- Template-Toolkit t/leak.t: 11/11 passing (was 9/11 — tests 5 & 9
  failed because TT stash updates with blessed temp values saw
  the temps DESTROYed mid-template).
- DBIx::Class t/52leaks.t: still passing (unchanged).
- Moo: still passing (unchanged).
- All make unit tests pass.

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Root cause: RuntimeScalar.addToArray and RuntimeArray.add(RuntimeScalar)
deferred refCount tracking to createReferenceWithTrackedElements, which
runs only AFTER all array literal elements are emitted.

During array literal construction `[ Parent->new(2), Parent->new(3) ]`,
each sub call's interior assignments (e.g. `my $s = bless {}; $s->{CHILD}
= Obj->new(...)`) trigger MortalList.flush() via setLargeRefCounted.
That flush processes pending decrements from earlier-constructed
elements (Parent 2, Obj 2) that were already sitting in the array's
elements list but whose refCount was still only 1 (from bless). The
flush drives their refCount to 0 and fires DESTROY — even though the
array IS going to own them once construction finishes.

Fix: incref referents at add-time (in both RuntimeScalar.addToArray's
PLAIN_ARRAY case and RuntimeArray.add(RuntimeScalar)) so intermediate
flushes see refCount ≥ 2 and leave them alone.
incrementRefCountForContainerStore is idempotent (skips
refCountOwned=true), so the final pass in
createReferenceWithTrackedElements is a no-op for eagerly-incref'd
elements.

Also reverted the explicit MortalList.flush() I added yesterday to the
setFromList fast path's finally block — it was too aggressive (firing
on every sub entry) and with the new add-time incref, is no longer
needed for the TT leak.t repro.

Minimal repro:

    package P;
    sub new { my ($c,$id)=@_; my $s=bless{id=>$id},$c;
              $s->{CHILD}=Obj->new($id); $s }
    my $arr = [ P->new(2), P->new(3) ];
    # DESTROY 2 fired mid-construction before this fix

Test impact:
- Template-Toolkit: Files=106, Tests=2920, all PASS (was failing
  chomp.t / directive.t with "Can't call method clone on undef").
- Moo: Files=71, Tests=841, PASS.
- DBIx::Class t/52leaks.t: 11/11 PASS, no leaks detected.
- All make unit tests pass.

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…ssion

Replaces the add-time incref approach from c8f669b (which was too broad
and incremented refCounts in arg-passing paths — causing CDBI t/02-Film.t
to lose DESTROY warnings because the blessed `$btaste3` never reached
refCount=0 at block exit).

New approach: wrap anon array/hash literal emission in
`MortalList.suppressFlush(true/false)` bytecode calls, targeted
narrowly at the literal construction itself. During this window,
pending mortal decrements from earlier-evaluated elements (e.g.,
`Foo->new()` return values) are held until after
`createReferenceWithTrackedElements` has bumped element refCounts —
at which point flushing resumes and decrements are processed
correctly.

Verified:
- DBIx::Class: Files=314, Tests=13804, PASS (cdbi/02-Film.t tests
  70-71 pass; txn_scope_guard.t test 18 passes).
- Moo: Files=71, Tests=841, PASS.
- Template-Toolkit: Files=106, Tests=2920, PASS (both leak.t and
  directive.t still clean).
- make unit tests pass.

Reverts the broad incref in RuntimeScalar.addToArray and
RuntimeArray.add(RuntimeScalar).

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