Skip to content

docs(session): correct the JIT note now that the bug has been measured #22

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
lisachenko wants to merge 1 commit into
base: main
Choose a base branch
from
+13 −6
Draft

docs(session): correct the JIT note now that the bug has been measured #22

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
19 changes: 13 additions & 6 deletions src/Session/Handler/CommandHandler.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -31,12 +31,19 @@
* ResumeMode they record. Anything less identical gets its own class.
*
* Implementations back $commands with a plain `private(set)` property carrying a
* constant default, NOT a computed get hook. Deliberately so: a hooked property read
* polymorphically across every handler class is a megamorphic hook site, which PHP
* 8.5's tracing JIT miscompiles (the full test suite segfaults inside JIT-emitted
* code with opcache.jit=tracing; plain properties are immune). Only the DEBUGGEE
* needs JIT off - phpunit and any IDE-side tooling are ordinary PHP processes where
* JIT is legitimately on, so the handlers must survive it.
* constant default, NOT a computed `get` hook. Deliberately so, and the reason is an
* engine bug rather than taste: with hooks here, PHP 8.5.9 segfaults the test process
* ~9 runs in 10 by jumping into the opcache/JIT mapping at bytes that are not code.
* Measured on this tree - hooks 8/8 crashes, plain properties 0/8; every opcache.jit
* mode and level reproduces it (function JIT at 1201 included, so it is not a tracing
* or trace-buffer problem), jit=off never does, and the trigger appears between 19 and
* 20 hooked classes rather than at any single one. Only the DEBUGGEE needs JIT off -
* phpunit and IDE-side tooling are ordinary PHP processes where JIT is legitimately
* on, so these classes have to survive it.
*
* Not yet minimized to a standalone script: synthetic replicas of this shape do not
* crash, so something about the surrounding process is required too. Restore the hooks
* only against a PHP that has been shown to survive them.
*/
interface CommandHandler
{
Expand Down
Loading