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GeezerVison is showing github.com — Zend: user opcode DISPATCH runs on a stale frame in the TAILCALL VM. by devnexen · Pull Request #24109 · php/php-src

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@devnexen

@devnexen devnexen commented Oct 3, 2026

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Fix #24081

ZEND_VM_DISPATCH() ran the CALL variant of the handler and returned its next opline to execute_ex(), whose execute_data still pointed at the entry frame. It now tail calls the TAILCALL variant of the handler.

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@devnexen
Zend: user opcode DISPATCH runs on a stale frame in the TAILCALL VM.
9512c51 
Fix php#24081

ZEND_VM_DISPATCH() ran the CALL variant of the handler and returned its
next opline to execute_ex(), whose execute_data still pointed at the
entry frame. It now tail calls the TAILCALL variant of the handler.
@github-actions github-actions Bot added Category: Engine ABI break labels Oct 3, 2026
@devnexen devnexen linked an issue Oct 3, 2026 that may be closed by this pull request
[Bug] User opcode handlers resume execution against a stale frame under ZEND_VM_KIND_TAILCALL #24081
Closed
@devnexen
add test
5952ca9
@github-actions github-actions Bot added the Extension: zend_test label Oct 3, 2026
@devnexen
fix test attempt
9481086
@devnexen
devnexen marked this pull request as ready for review October 4, 2026 06:21
@devnexen
devnexen requested a review from dstogov as a code owner October 4, 2026 06:21
@devnexen
devnexen requested a review from arnaud-lb October 4, 2026 06:21
This was referenced Oct 4, 2026
feat: PHP 8.6 support for user opcode hooks (tail-call VM bug diagnosed, fixed upstream) lisachenko/z-engine#281
Merged
User opcode handlers corrupt VM state under PHP 8.6's tail-call VM (macOS arm64) lisachenko/z-engine#280
Closed
arnaud-lb
arnaud-lb approved these changes Oct 9, 2026
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Looks good to me!

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@arnaud-lb

arnaud-lb commented Oct 9, 2026

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NB: This should target 8.5
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@devnexen devnexen closed this in 2cf7ad0 Oct 9, 2026
@LamentXU123

LamentXU123 commented Oct 10, 2026

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Hey! This is causing test failure in arm CI. https://app.circleci.com/pipelines/github/php/php-src/35749/workflows/4693c978-fcc7-4f13-afeb-64d14f914b5b/jobs/35387 Ideas ? @devnexen @arnaud-lb
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@devnexen

devnexen commented Oct 10, 2026 •
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I think can be fixed with zend_test.observer.show_output=1 (just because I remember someone fixed case like this that way not so long ago). will push a PR soon-ish
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@devnexen
devnexen deleted the gh24081 branch October 10, 2026 08:12
lisachenko pushed a commit to lisachenko/z-engine that referenced this pull request Oct 10, 2026
@claude
feat(hook): retire the tail-call VM guard - php-src fixed the dispatch (
b005b3c 
#280)

php/php-src#24109 (merged into PHP-8.6 as 2cf7ad0) makes the generated
ZEND_USER_OPCODE_SPEC_TAILCALL_HANDLER resume the DISPATCH result inside
the tail-call chain instead of returning it to execute_ex()'s stale
frame, so OpCode::setHandler() no longer needs to refuse on
VM_KIND_TAILCALL. Remove the guard, its exception factory, the issue-280
probe ladder and the dispatch-only diagnose workflow; keep Core::vmKind()
as plain engine introspection, and keep the every-leg hook coverage the
guard test introduced as OpCodeHookLifecycleTest (the gap that let #280
ship unnoticed was that all other hook tests are internal-group only).
Docs now record the bug as fixed upstream rather than as a live caveat.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01U4cKi87mVQ896uSrw592fG
lisachenko pushed a commit to lisachenko/zdebug that referenced this pull request Oct 10, 2026
@claude
ci: require the macOS arm64 + PHP 8.6 leg - upstream tail-call VM bug…
ec393d2 
… fixed

php-src fixed the user-opcode dispatch under the tail-call VM
(lisachenko/z-engine#280, resolved by php/php-src#24109 merged into
PHP-8.6), and current 8.6 nightlies run engine hooks cleanly on Apple
Silicon, so the experimental escape hatch comes off: the arm64 + 8.6 leg
fails the workflow like every other leg again. Docs record the bug as
fixed instead of as a platform exception.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01U4cKi87mVQ896uSrw592fG
@lisachenko lisachenko mentioned this pull request Oct 10, 2026
ci: test ZDebug on the PHP 8.6 beta via z-engine 8.6.x-dev lisachenko/zdebug#24
Merged
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@arnaud-lb arnaud-lb arnaud-lb approved these changes
@dstogov dstogov Awaiting requested review from dstogov dstogov is a code owner

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ABI break Category: Engine Extension: zend_test

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[Bug] User opcode handlers resume execution against a stale frame under ZEND_VM_KIND_TAILCALL

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3 participants

@devnexen @arnaud-lb @LamentXU123
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