From: "Mattias Engdegård" <mattiase@acm.org>
To: Paul Eggert <eggert@cs.ucla.edu>,
Stefan Monnier <monnier@IRO.UMontreal.CA>
Cc: 34781-done@debbugs.gnu.org
Subject: bug#34781: 27.0.50; integer in pcase sometimes compared by eq
Date: Fri, 29 Mar 2019 00:03:01 +0100 [thread overview]
Message-ID: <821c6aaec1660201230fe27a7e11105c70ccfe4f.camel@acm.org> (raw)
In-Reply-To: <96bb53d6-c1dc-097a-fadd-252aa1a81313@cs.ucla.edu>
[-- Attachment #1: Type: text/plain, Size: 419 bytes --]
tor 2019-03-28 klockan 15:38 -0700 skrev Paul Eggert:
> On 3/28/19 3:20 PM, Mattias Engdegård wrote:
> > I'll do the obvious (unless you beat me to it).
>
> When you do that, please also change the name of the local from memq-
> ok
> to memql-ok, for clarity. Thanks.
Done. Thanks for your help! I'm attaching the mostly cleaned-up patch
(minus the necessary doc changes), in case someone will see some use
for it.
[-- Attachment #2: 0001-Add-bounds-for-portable-fixnums-and-portable-fixnum-.patch --]
[-- Type: text/x-patch, Size: 3863 bytes --]
From a60e78be5dfc2172345d140f2cd8df0a77bea0a1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mattias=20Engdeg=C3=A5rd?= <mattiase@acm.org>
Date: Thu, 28 Mar 2019 22:12:37 +0100
Subject: [PATCH] Add bounds for portable fixnums, and portable-fixnum-p
These are useful for macros that need to detect whether a number is a
fixnum on any machine, so that the bytecode becomes portable (Bug#34781).
* src/data.c (most-positive-portable-fixnum, most-negative-portable-fixnum):
* lisp/subr.el (portable-fixnum-p):
New.
* etc/NEWS (Lisp Changes): Mention portable-fixnum-p.
---
etc/NEWS | 5 +++++
lisp/subr.el | 5 +++++
src/data.c | 24 ++++++++++++++++++++++++
3 files changed, 34 insertions(+)
diff --git a/etc/NEWS b/etc/NEWS
index 7486d6bcfe..2ab3c5b4bb 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1424,6 +1424,11 @@ like 'file-attributes' that compute file sizes and other attributes,
functions like 'process-id' that compute process IDs, and functions like
'user-uid' and 'group-gid' that compute user and group IDs.
+Since the size of fixnums varies between platforms, the new predicate
+'portable-fixnum-p' determines whether a number is a fixnum on any
+machine running the current Emacs version. The corresponding bounds
+are 'most-negative-portable-fixnum' and 'most-negative-portable-fixnum'.
+
+++
** Although the default timestamp format is still (HI LO US PS),
it is planned to change in a future Emacs version, to exploit bignums.
diff --git a/lisp/subr.el b/lisp/subr.el
index f1a1dddd81..efa9cd4065 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -376,6 +376,11 @@ bignump
"Return t if OBJECT is a bignum."
(and (integerp object) (not (fixnump object))))
+(defun portable-fixnum-p (object)
+ "Return t if OBJECT is a fixnum on any machine running this Emacs version."
+ (and (integerp object)
+ (<= most-negative-portable-fixnum object most-positive-portable-fixnum)))
+
(defun lsh (value count)
"Return VALUE with its bits shifted left by COUNT.
If COUNT is negative, shifting is actually to the right.
diff --git a/src/data.c b/src/data.c
index 15b6106cfe..6d50a14bde 100644
--- a/src/data.c
+++ b/src/data.c
@@ -4110,6 +4110,30 @@ This variable cannot be set; trying to do so will signal an error. */);
Vmost_negative_fixnum = make_fixnum (MOST_NEGATIVE_FIXNUM);
make_symbol_constant (intern_c_string ("most-negative-fixnum"));
+ /* The smallest portable value of EMACS_INT_MAX. */
+ int least_emacs_int_max = 2147483647; /* 2**31 - 1 */
+
+ /* Largest and smallest values that are guaranteed to be representable
+ as fixnums on any machine. */
+ int most_positive_portable_fixnum = least_emacs_int_max >> INTTYPEBITS;
+ int most_negative_portable_fixnum = -1 - most_positive_portable_fixnum;
+
+ DEFVAR_LISP ("most-positive-portable-fixnum",
+ Vmost_positive_portable_fixnum,
+ doc: /* The largest integer representable as a fixnum on any platform.
+This variable can be used to ensure portability of bytecode that works
+with fixnums. It cannot be set; trying to do so will signal an error. */);
+ Vmost_positive_portable_fixnum = make_fixnum (most_positive_portable_fixnum);
+ make_symbol_constant (intern_c_string ("most-positive-portable-fixnum"));
+
+ DEFVAR_LISP ("most-negative-portable-fixnum",
+ Vmost_negative_portable_fixnum,
+ doc: /* The least integer representable as a fixnum on any platform.
+This variable can be used to ensure portability of bytecode that works
+with fixnums. It cannot be set; trying to do so will signal an error. */);
+ Vmost_negative_portable_fixnum = make_fixnum (most_negative_portable_fixnum);
+ make_symbol_constant (intern_c_string ("most-negative-portable-fixnum"));
+
DEFSYM (Qwatchers, "watchers");
DEFSYM (Qmakunbound, "makunbound");
DEFSYM (Qunlet, "unlet");
--
2.20.1
next prev parent reply other threads:[~2019-03-28 23:03 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 15:13 bug#34781: 27.0.50; integer in pcase sometimes compared by eq Mattias Engdegård
[not found] ` <handler.34781.B.15519717565134.ack@debbugs.gnu.org>
2019-03-12 12:24 ` bug#34781: Acknowledgement (27.0.50; integer in pcase sometimes compared by eq) Mattias Engdegård
2019-03-16 19:09 ` bug#34781: 27.0.50; integer in pcase sometimes compared by eq Mattias Engdegård
2019-03-28 18:25 ` Paul Eggert
2019-03-28 19:47 ` Michael Heerdegen
2019-03-28 20:33 ` Paul Eggert
2019-03-28 21:30 ` Michael Heerdegen
2019-03-28 19:51 ` Mattias Engdegård
2019-03-28 20:30 ` Paul Eggert
2019-03-28 21:51 ` Mattias Engdegård
2019-03-28 22:10 ` Paul Eggert
2019-03-28 22:11 ` Stefan Monnier
2019-03-28 22:20 ` Mattias Engdegård
2019-03-28 22:38 ` Paul Eggert
2019-03-28 23:03 ` Mattias Engdegård [this message]
2019-03-29 8:48 ` Eli Zaretskii
2019-03-29 9:52 ` Mattias Engdegård
2019-03-29 12:33 ` Eli Zaretskii
2019-03-28 19:43 ` Michael Heerdegen
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