Re: [BUG] Too agressive byte code optimizer

Y> When following form is eval'ed, it signals an error: Y> Wrong type argument: number-char-or-marker-p, a Y> (= 'a) Y> However, if it's byte-compiled, it returns t. Y> (disassemble (byte-compile (lambda () (= 'a)))) Y> shows: Y> byte code: Y> args: nil Y> 0 constant t Y> 1 return Y> Martin? `byte-compile-delete-errors' is a variable declared in Lisp. -- loaded from "bytecomp" Value: t Documentation: *If non-nil, the optimizer may delete forms that may signal an error. This includes variable references and calls to functions such as `car'. There is already this code in byte-plus that optimizes (+ x) ==> x (case elt (0 (when (not byte-compile-delete-errors) (byte-compile-constant 0) (byte-compile-out 'byte-plus 0))) (+1 (byte-compile-out 'byte-add1 0)) (-1 (byte-compile-out 'byte-sub1 0)) (= x) should work the same way. You can also argue that if the argument (or arguments) is/are CONSTANT, then there should be compile-time evaluation. I haven't implemented that in this patch. Index: lisp/ChangeLog =================================================================== RCS file: /usr/CVSroot/XEmacs/xemacs/lisp/ChangeLog,v retrieving revision 1.292 diff -u -w -U0 -r1.292 ChangeLog --- lisp/ChangeLog 2001/05/20 01:17:07 1.292 +++ lisp/ChangeLog 2001/05/20 06:01:49 ＠＠ -0,0 +1,5 ＠＠ +2001-05-20 Martin Buchholz <martin(a)xemacs.org&gt; + + * bytecomp.el (byte-compile-arithcompare): + Only optimize (= x) ==> t if byte-compile-delete-errors is nil. + Index: lisp/bytecomp.el =================================================================== RCS file: /usr/CVSroot/XEmacs/xemacs/lisp/bytecomp.el,v retrieving revision 1.12 diff -u -w -r1.12 bytecomp.el --- lisp/bytecomp.el 2001/05/04 22:41:59 1.12 +++ lisp/bytecomp.el 2001/05/20 06:02:18 ＠＠ -3205,7 +3205,9 ＠＠ (defun byte-compile-arithcompare (form) (case (length (cdr form)) (0 (byte-compile-subr-wrong-args form "1 or more")) - (1 (byte-compile-constant t)) + (1 (if byte-compile-delete-errors + (byte-compile-constant t) + (byte-compile-normal-call form))) (2 (byte-compile-two-args form)) (t (byte-compile-normal-call form))))