From 2b7edea1c2559b79f52d0094b5ba2cd0d6700bd2 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Mon, 6 Feb 2017 17:15:14 -0800 Subject: [PATCH] Make FOR_EACH_TAIL more like other FOR_EACH macros MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit See comments by Stefan Monnier in: http://lists.gnu.org/archive/html/emacs-devel/2017-02/msg00181.html and by Eli Zaretskii in: http://lists.gnu.org/archive/html/emacs-devel/2017-02/msg00207.html * src/fns.c (internal_equal): Do not bypass check for depth overflow when tail-recursing via a dotted list tail or an overlay plist, to avoid a rare infloop. * src/lisp.h (FOR_EACH_TAIL, FOR_EACH_TAIL_SAFE): Take TAIL as an arg, and update it at each iteration, rather than have callers access it.tail. All callers changed. (FOR_EACH_TAIL): Do not check for dotted lists, as this is now the caller’s responsibility. All callers changed. (FOR_EACH_TAIL_CONS): Remove. All callers changed. (struct for_each_tail_internal.tail): Remove; no longer needed. (FOR_EACH_TAIL_INTERNAL): Remove dotted arg, and set the tail arg each time through the loop. All callers changed. --- src/fns.c | 182 +++++++++++++++++++++++++++++++++--------------------------- src/lisp.h | 48 +++++++--------- src/xdisp.c | 4 +- 3 files changed, 123 insertions(+), 111 deletions(-) diff --git a/src/fns.c b/src/fns.c index b5508fb..ffe3218 100644 --- a/src/fns.c +++ b/src/fns.c @@ -111,6 +111,7 @@ To get the number of bytes, use `string-bytes'. */) intptr_t i = 0; FOR_EACH_TAIL (sequence) i++; + CHECK_LIST_END (sequence, sequence); if (MOST_POSITIVE_FIXNUM < i) error ("List too long"); val = make_number (i); @@ -1343,9 +1344,11 @@ DEFUN ("member", Fmember, Smember, 2, 2, 0, The value is actually the tail of LIST whose car is ELT. */) (Lisp_Object elt, Lisp_Object list) { - FOR_EACH_TAIL (list) - if (! NILP (Fequal (elt, XCAR (li.tail)))) - return li.tail; + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) + if (! NILP (Fequal (elt, XCAR (tail)))) + return tail; + CHECK_LIST_END (tail, list); return Qnil; } @@ -1354,9 +1357,11 @@ DEFUN ("memq", Fmemq, Smemq, 2, 2, 0, The value is actually the tail of LIST whose car is ELT. */) (Lisp_Object elt, Lisp_Object list) { - FOR_EACH_TAIL (list) - if (EQ (XCAR (li.tail), elt)) - return li.tail; + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) + if (EQ (XCAR (tail), elt)) + return tail; + CHECK_LIST_END (tail, list); return Qnil; } @@ -1368,12 +1373,14 @@ The value is actually the tail of LIST whose car is ELT. */) if (!FLOATP (elt)) return Fmemq (elt, list); - FOR_EACH_TAIL (list) + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) { - Lisp_Object tem = XCAR (li.tail); + Lisp_Object tem = XCAR (tail); if (FLOATP (tem) && internal_equal (elt, tem, 0, 0, Qnil)) - return li.tail; + return tail; } + CHECK_LIST_END (tail, list); return Qnil; } @@ -1383,9 +1390,11 @@ The value is actually the first element of LIST whose car is KEY. Elements of LIST that are not conses are ignored. */) (Lisp_Object key, Lisp_Object list) { - FOR_EACH_TAIL (list) - if (CONSP (XCAR (li.tail)) && EQ (XCAR (XCAR (li.tail)), key)) - return XCAR (li.tail); + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) + if (CONSP (XCAR (tail)) && EQ (XCAR (XCAR (tail)), key)) + return XCAR (tail); + CHECK_LIST_END (tail, list); return Qnil; } @@ -1406,13 +1415,15 @@ DEFUN ("assoc", Fassoc, Sassoc, 2, 2, 0, The value is actually the first element of LIST whose car equals KEY. */) (Lisp_Object key, Lisp_Object list) { - FOR_EACH_TAIL (list) + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) { - Lisp_Object car = XCAR (li.tail); + Lisp_Object car = XCAR (tail); if (CONSP (car) && (EQ (XCAR (car), key) || !NILP (Fequal (XCAR (car), key)))) return car; } + CHECK_LIST_END (tail, list); return Qnil; } @@ -1437,9 +1448,11 @@ DEFUN ("rassq", Frassq, Srassq, 2, 2, 0, The value is actually the first element of LIST whose cdr is KEY. */) (Lisp_Object key, Lisp_Object list) { - FOR_EACH_TAIL (list) - if (CONSP (XCAR (li.tail)) && EQ (XCDR (XCAR (li.tail)), key)) - return XCAR (li.tail); + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) + if (CONSP (XCAR (tail)) && EQ (XCDR (XCAR (tail)), key)) + return XCAR (tail); + CHECK_LIST_END (tail, list); return Qnil; } @@ -1448,13 +1461,15 @@ DEFUN ("rassoc", Frassoc, Srassoc, 2, 2, 0, The value is actually the first element of LIST whose cdr equals KEY. */) (Lisp_Object key, Lisp_Object list) { - FOR_EACH_TAIL (list) + Lisp_Object tail = list; + FOR_EACH_TAIL (tail) { - Lisp_Object car = XCAR (li.tail); + Lisp_Object car = XCAR (tail); if (CONSP (car) && (EQ (XCDR (car), key) || !NILP (Fequal (XCDR (car), key)))) return car; } + CHECK_LIST_END (tail, list); return Qnil; } @@ -1470,21 +1485,22 @@ the value of a list `foo'. See also `remq', which does not modify the argument. */) (Lisp_Object elt, Lisp_Object list) { - Lisp_Object prev = Qnil; + Lisp_Object prev = Qnil, tail = list; - FOR_EACH_TAIL (list) + FOR_EACH_TAIL (tail) { - Lisp_Object tem = XCAR (li.tail); + Lisp_Object tem = XCAR (tail); if (EQ (elt, tem)) { if (NILP (prev)) - list = XCDR (li.tail); + list = XCDR (tail); else - Fsetcdr (prev, XCDR (li.tail)); + Fsetcdr (prev, XCDR (tail)); } else - prev = li.tail; + prev = tail; } + CHECK_LIST_END (tail, list); return list; } @@ -1592,20 +1608,21 @@ changing the value of a sequence `foo'. */) } else { - Lisp_Object prev = Qnil; + Lisp_Object prev = Qnil, tail = seq; - FOR_EACH_TAIL (seq) + FOR_EACH_TAIL (tail) { - if (!NILP (Fequal (elt, (XCAR (li.tail))))) + if (!NILP (Fequal (elt, XCAR (tail)))) { if (NILP (prev)) - seq = XCDR (li.tail); + seq = XCDR (tail); else - Fsetcdr (prev, XCDR (li.tail)); + Fsetcdr (prev, XCDR (tail)); } else - prev = li.tail; + prev = tail; } + CHECK_LIST_END (tail, seq); } return seq; @@ -1678,7 +1695,8 @@ See also the function `nreverse', which is used more often. */) { new = Qnil; FOR_EACH_TAIL (seq) - new = Fcons (XCAR (li.tail), new); + new = Fcons (XCAR (seq), new); + CHECK_LIST_END (seq, seq); } else if (VECTORP (seq)) { @@ -1930,14 +1948,15 @@ corresponding to the given PROP, or nil if PROP is not one of the properties on the list. This function never signals an error. */) (Lisp_Object plist, Lisp_Object prop) { - FOR_EACH_TAIL_SAFE (plist) + Lisp_Object tail = plist; + FOR_EACH_TAIL_SAFE (tail) { - if (! CONSP (XCDR (li.tail))) + if (! CONSP (XCDR (tail))) break; - if (EQ (prop, XCAR (li.tail))) - return XCAR (XCDR (li.tail)); - li.tail = XCDR (li.tail); - if (EQ (li.tail, li.tortoise)) + if (EQ (prop, XCAR (tail))) + return XCAR (XCDR (tail)); + tail = XCDR (tail); + if (EQ (tail, li.tortoise)) break; } @@ -1963,23 +1982,24 @@ use `(setq x (plist-put x prop val))' to be sure to use the new value. The PLIST is modified by side effects. */) (Lisp_Object plist, Lisp_Object prop, Lisp_Object val) { - Lisp_Object prev = Qnil; - FOR_EACH_TAIL_CONS (plist) + Lisp_Object prev = Qnil, tail = plist; + FOR_EACH_TAIL (tail) { - if (! CONSP (XCDR (li.tail))) + if (! CONSP (XCDR (tail))) break; - if (EQ (prop, XCAR (li.tail))) + if (EQ (prop, XCAR (tail))) { - Fsetcar (XCDR (li.tail), val); + Fsetcar (XCDR (tail), val); return plist; } - prev = li.tail; - li.tail = XCDR (li.tail); - if (EQ (li.tail, li.tortoise)) + prev = tail; + tail = XCDR (tail); + if (EQ (tail, li.tortoise)) circular_list (plist); } + CHECK_LIST_END (tail, plist); Lisp_Object newcell = Fcons (prop, Fcons (val, NILP (prev) ? plist : XCDR (XCDR (prev)))); if (NILP (prev)) @@ -2007,16 +2027,20 @@ corresponding to the given PROP, or nil if PROP is not one of the properties on the list. */) (Lisp_Object plist, Lisp_Object prop) { - FOR_EACH_TAIL_CONS (plist) + Lisp_Object tail = plist; + FOR_EACH_TAIL (tail) { - if (! CONSP (XCDR (li.tail))) + if (! CONSP (XCDR (tail))) break; - if (! NILP (Fequal (prop, XCAR (li.tail)))) - return XCAR (XCDR (li.tail)); - li.tail = XCDR (li.tail); - if (EQ (li.tail, li.tortoise)) + if (! NILP (Fequal (prop, XCAR (tail)))) + return XCAR (XCDR (tail)); + tail = XCDR (tail); + if (EQ (tail, li.tortoise)) circular_list (plist); } + + CHECK_LIST_END (tail, plist); + return Qnil; } @@ -2030,23 +2054,24 @@ use `(setq x (lax-plist-put x prop val))' to be sure to use the new value. The PLIST is modified by side effects. */) (Lisp_Object plist, Lisp_Object prop, Lisp_Object val) { - Lisp_Object prev = Qnil; - FOR_EACH_TAIL_CONS (plist) + Lisp_Object prev = Qnil, tail = plist; + FOR_EACH_TAIL (tail) { - if (! CONSP (XCDR (li.tail))) + if (! CONSP (XCDR (tail))) break; - if (! NILP (Fequal (prop, XCAR (li.tail)))) + if (! NILP (Fequal (prop, XCAR (tail)))) { - Fsetcar (XCDR (li.tail), val); + Fsetcar (XCDR (tail), val); return plist; } - prev = li.tail; - li.tail = XCDR (li.tail); - if (EQ (li.tail, li.tortoise)) + prev = tail; + tail = XCDR (tail); + if (EQ (tail, li.tortoise)) circular_list (plist); } + CHECK_LIST_END (tail, plist); Lisp_Object newcell = list2 (prop, val); if (NILP (prev)) return newcell; @@ -2095,6 +2120,7 @@ static bool internal_equal (Lisp_Object o1, Lisp_Object o2, int depth, bool props, Lisp_Object ht) { + tail_recurse: if (depth > 10) { if (depth > 200) @@ -2123,7 +2149,6 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, int depth, bool props, } } - tail_recurse: if (EQ (o1, o2)) return 1; if (XTYPE (o1) != XTYPE (o2)) @@ -2144,20 +2169,16 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, int depth, bool props, case Lisp_Cons: { - Lisp_Object tail1 = o1; - FOR_EACH_TAIL_CONS (o1) + FOR_EACH_TAIL (o1) { if (! CONSP (o2)) return false; - if (! internal_equal (XCAR (li.tail), XCAR (o2), depth + 1, - props, ht)) + if (! internal_equal (XCAR (o1), XCAR (o2), depth + 1, props, ht)) return false; - tail1 = XCDR (li.tail); o2 = XCDR (o2); - if (EQ (tail1, o2)) + if (EQ (XCDR (o1), o2)) return true; } - o1 = tail1; depth++; goto tail_recurse; } @@ -2340,8 +2361,8 @@ usage: (nconc &rest LISTS) */) CHECK_CONS (tem); Lisp_Object tail; - FOR_EACH_TAIL_CONS (tem) - tail = li.tail; + FOR_EACH_TAIL (tem) + tail = tem; tem = args[argnum + 1]; Fsetcdr (tail, tem); @@ -2763,19 +2784,18 @@ property and a property with the value nil. The value is actually the tail of PLIST whose car is PROP. */) (Lisp_Object plist, Lisp_Object prop) { - FOR_EACH_TAIL (plist) + Lisp_Object tail = plist; + FOR_EACH_TAIL (tail) { - if (EQ (XCAR (li.tail), prop)) - return li.tail; - if (!CONSP (XCDR (li.tail))) - { - CHECK_LIST_END (XCDR (li.tail), plist); - return Qnil; - } - li.tail = XCDR (li.tail); - if (EQ (li.tail, li.tortoise)) - circular_list (plist); + if (EQ (XCAR (tail), prop)) + return tail; + tail = XCDR (tail); + if (! CONSP (tail)) + break; + if (EQ (tail, li.tortoise)) + circular_list (tail); } + CHECK_LIST_END (tail, plist); return Qnil; } diff --git a/src/lisp.h b/src/lisp.h index b753971..f1e2685 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -4580,41 +4580,33 @@ enum Lisp_String)) \ : make_unibyte_string (str, len)) -/* Loop over tails of LIST, checking for dotted lists and cycles, - and possibly quitting after each loop iteration. - In the loop body, ‘li.tail’ is the current cons; the name ‘li’ is - short for “list iterator”. The expression LIST may be evaluated - more than once, and so should not have side effects. The loop body +/* Loop over conses of the list TAIL, signaling if a cycle is found, + and possibly quitting after each loop iteration. In the loop body, + set TAIL to the current cons. If the loop exits normally, + set TAIL to the terminating non-cons, typically nil. The loop body should not modify the list’s top level structure other than by perhaps deleting the current cons. */ -#define FOR_EACH_TAIL(list) \ - FOR_EACH_TAIL_INTERNAL (list, CHECK_LIST_END (li.tail, list), \ - circular_list (list), true) +#define FOR_EACH_TAIL(tail) \ + FOR_EACH_TAIL_INTERNAL (tail, circular_list (tail), true) -/* Like FOR_EACH_TAIL (LIST), except do not check for dotted lists. */ +/* Like FOR_EACH_TAIL (LIST), except do not signal or quit. + If the loop exits due to a cycle, TAIL’s value is undefined. */ -#define FOR_EACH_TAIL_CONS(list) \ - FOR_EACH_TAIL_INTERNAL (list, (void) 0, circular_list (list), true) - -/* Like FOR_EACH_TAIL (LIST), except check for neither dotted lists - nor cycles, and do not quit. */ - -#define FOR_EACH_TAIL_SAFE(list) \ - FOR_EACH_TAIL_INTERNAL (list, (void) 0, (void) (li.tail = Qnil), false) +#define FOR_EACH_TAIL_SAFE(tail) \ + FOR_EACH_TAIL_INTERNAL (tail, (void) ((tail) = Qnil), false) /* Iterator intended for use only within FOR_EACH_TAIL_INTERNAL. */ struct for_each_tail_internal { - Lisp_Object tail, tortoise; + Lisp_Object tortoise; intptr_t max, n; unsigned short int q; }; -/* Like FOR_EACH_TAIL (LIST), except evaluate DOTTED or CYCLE, - respectively, if a dotted list or cycle is found, and check for - quit if CHECK_QUIT. This is an internal macro intended for use - only by the above macros. +/* Like FOR_EACH_TAIL (LIST), except evaluate CYCLE if a cycle is + found, and check for quit if CHECK_QUIT. This is an internal macro + intended for use only by the above macros. Use Brent’s teleporting tortoise-hare algorithm. See: Brent RP. BIT. 1980;20(2):176-84. doi:10.1007/BF01933190 @@ -4626,15 +4618,15 @@ struct for_each_tail_internal other noninterruptible areas (e.g., garbage collection) that there is little point to calling maybe_quit here. */ -#define FOR_EACH_TAIL_INTERNAL(list, dotted, cycle, check_quit) \ - for (struct for_each_tail_internal li = { list, list, 2, 0, 2 }; \ - CONSP (li.tail) || (dotted, false); \ - (li.tail = XCDR (li.tail), \ +#define FOR_EACH_TAIL_INTERNAL(tail, cycle, check_quit) \ + for (struct for_each_tail_internal li = { tail, 2, 0, 2 }; \ + CONSP (tail); \ + ((tail) = XCDR (tail), \ ((--li.q != 0 \ || ((check_quit) ? maybe_quit () : (void) 0, 0 < --li.n) \ || (li.q = li.n = li.max <<= 1, li.n >>= USHRT_WIDTH, \ - li.tortoise = li.tail, false)) \ - && EQ (li.tail, li.tortoise)) \ + li.tortoise = (tail), false)) \ + && EQ (tail, li.tortoise)) \ ? (cycle) : (void) 0)) /* Do a `for' loop over alist values. */ diff --git a/src/xdisp.c b/src/xdisp.c index 5e1207f..387a370 100644 --- a/src/xdisp.c +++ b/src/xdisp.c @@ -23040,10 +23040,10 @@ display_mode_element (struct it *it, int depth, int field_width, int precision, n += display_mode_element (it, depth, /* Pad after only the last list element. */ - (! CONSP (XCDR (li.tail)) + (! CONSP (XCDR (elt)) ? field_width - n : 0), - precision - n, XCAR (li.tail), + precision - n, XCAR (elt), props, risky); } } -- 2.9.3