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tests: add a regression test for an encountered issue

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This issue was never manifestable in develop branch.
This commit is contained in:
Daniel Kochmański 2025-05-09 13:01:49 +02:00
parent fdf7c77909
commit aefcd77e02
1 changed files with 44 additions and 0 deletions
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src/tests/normal-tests/mixed.lsp
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@ -594,3 +594,47 @@
(read stream t nil t)))
t)
(finishes (read-from-string "#x123"))))
;;; Author: Daniel Kochmański
;;; Created: 2025-05-09
;;; Issue: https://gitlab.com/embeddable-common-lisp/ecl/-/merge_requests/346#note_2492489716
;;; Description
;;;
;;; Moving locals from heap to the stack revealed an issue where stack
;;; frames are invalidated after the lisp stack is resized. That causes
;;; a risk of local variables to be garbage collected.
;;;
;;; | Call DO-ENTRIES* | #x1000 [TRASH] | #x1000 [TRASH] |
;;; | Resize the stack | #x1000 [TRASH] | #x2000 [TRASH] |
;;; | Bind a local var | #x1000 [value] | #x2000 [TRASH] |
;;; | Allocations-> GC | #x1000 [what?] | #x2000 [TRASH] |
;;; | Load a local var | #x1000 [what?] | #x2000 [TRASH] |
;;;
;;; We bind the variable after the stack has been resized, so when we copy the
;;; memory during the stack resize only [TRASH] is transferred.
;;;
;;; Since the lisp stack is allocated with ecl_alloc_atomic, referenced values must
;;; be explicitly marked -- and it is done so in ecl_mark_env. This is very sane
;;; thing to do, because if we had marked whole vector (even above top), then we'd
;;; retain old references, and generally we'd mark 32K instead of say 200 addresses.
;;;
;;; But, when we grow the stack, the old vector is replaced, and ecl_mark_env does
;;; not mark the old stack, effectively allowing to reuse up our [value] by GC.
;;;
;;; Note that usually stack frames are filled eagerly to complete argument list, so
;;; this issue is irrelevant to them (because we don't change values after resize),
;;; so this prolbem did not manifest itself until now.
(deftest mix.0031.invalidate-stack-frames ()
(macrolet ((ntimes (n form)
`(progn ,@(make-list n :initial-element form))))
(labels ((resize-lisp-stack ()
(let* ((old-limit (ext:get-limit 'ext:lisp-stack))
(new-limit (* old-limit 2)))
(ext:set-limit 'ext:lisp-stack new-limit)))
(invoke-test-case ()
(resize-lisp-stack)
(let ((n 0))
(ntimes 2048 (apply #'append (make-list 2048 :initial-element '(:foo))))
(is (typep n 'number)))))
(invoke-test-case))))