Fix GH-20112: Fatal error during autoloading of complex inheritance chain#21573
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iliaal wants to merge 1 commit intophp:PHP-8.4from
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Fix GH-20112: Fatal error during autoloading of complex inheritance chain#21573iliaal wants to merge 1 commit intophp:PHP-8.4from
iliaal wants to merge 1 commit intophp:PHP-8.4from
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This was referenced Mar 29, 2026
dstogov
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Sorry, I don't know the variance-related code of PHP well. I can't review this.
Zend/zend_globals.h
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| HashTable *delayed_variance_obligations; | ||
| HashTable *delayed_autoloads; | ||
| uint32_t delayed_autoloads_depth; |
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This is an ABI break. It's not allowed in minor stable releases.
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Moved the counter to a file-local ZEND_TLS uint32_t in zend_inheritance.c, so it stays per-thread without touching zend_compiler_globals. Same scope as CG(delayed_autoloads) itself, matching the pattern at zend_fibers.c:187.
…e chain When load_delayed_classes() is called recursively (e.g., autoloading a class whose linking triggers another class with unresolved variance), the shared delayed_autoloads table may contain entries from an outer caller whose dependencies are not yet available. The inner call would attempt to load these unrelated entries, causing a fatal error when their parent class is still mid-linking higher up the call stack. In nested calls, catch such loading failures and re-append the entry for the outer caller to process later, when the dependency chain is complete. A consecutive-failure counter ensures no infinite retry loops. The nesting depth counter is kept as a file-local ZEND_TLS variable rather than added to zend_compiler_globals, since PHP-8.4 forbids ABI changes. Closes phpGH-20112
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Fixes #20112
load_delayed_classes()iterates a sharedCG(delayed_autoloads)hash table. When autoloading triggers linking of another class with unresolved variance, the recursive call walks the same table and can pull entries that belong to an outer caller. If that entry's parent is still mid-linking up the call stack, the load hits a fatal error.The fix adds a nesting depth counter. At depth > 1, if a class doesn't load and isn't in the class table, we catch the exception and re-append the entry for the outer caller to pick up once its dependency chain completes. A consecutive-failure count breaks out when no progress is possible. At depth 1, failures propagate as before.
Targeting 8.4 since the bug has existed since PHP 8.1 (bisected to a38f4f9). No performance impact; the new code only runs on the exception path.