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Fix cond miscompilation bug

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This fixes a bug that miscompiled

  (cond ... C S1...Sn)

where S1...Sn are switch clauses (that can be compiled into a switch
op) and C a non-switch clause, by tucking on an extra copy of C at the
end.  This was a serious wrong-code bug when the condition of C had
side-effects; otherwise it was only a waste of time and space.

* lisp/emacs-lisp/bytecomp.el (byte-compile-cond): Fix.
* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp-tests--test-cases):
Add test case.
This commit is contained in:
Mattias Engdegård 2023-03-02 09:56:59 +01:00
parent a1d90e48bb
commit 828c49ae29
2 changed files with 10 additions and 0 deletions
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1
lisp/emacs-lisp/bytecomp.el
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@ -4590,6 +4590,7 @@ Return (TAIL VAR TEST CASES), where:
(if switch-prefix
(progn
(byte-compile-cond-jump-table (cdr switch-prefix) donetag)
(setq clause nil)
(setq clauses (car switch-prefix)))
(setq clause (car clauses))
(cond ((or (eq (car clause) t)

9
test/lisp/emacs-lisp/bytecomp-tests.el
View file

@ -757,6 +757,15 @@ inner loops respectively."
(bytecomp-test-identity 3)
(error 'bad)
(:success)) ; empty handler
;; `cond' miscompilation bug
(let ((fn (lambda (x)
(let ((y nil))
(cond ((progn (setq x (1+ x)) (> x 10)) (setq y 'a))
((eq x 1) (setq y 'b))
((eq x 2) (setq y 'c)))
(list x y)))))
(mapcar fn (bytecomp-test-identity '(0 1 2 3 10 11))))
)
"List of expressions for cross-testing interpreted and compiled code.")