From: Dmitry Antipov <dmantipov@yandex.ru>
To: Andreas Schwab <schwab@suse.de>
Cc: Emacs development discussions <emacs-devel@gnu.org>
Subject: Re: [RFC] temporary Lisp_Strings
Date: Tue, 02 Sep 2014 17:47:15 +0400 [thread overview]
Message-ID: <5405CA63.9090405@yandex.ru> (raw)
In-Reply-To: <mvm38canoo0.fsf@hawking.suse.de>
On 09/02/2014 05:21 PM, Andreas Schwab wrote:
> There is none. The stack could be in a completely different address
> region that may not be suitable in non-USE_LSB_TAG configurations.
IIUC non-USE_LSB_TAG configurations are not widely used, so this is
a tier-2 problem.
>> +#define alloca_string(str) \
>> + ({ Lisp_Object string; \
>> + struct Lisp_String *s; \
>> + ptrdiff_t nchars, nbytes, size = strlen (str); \
>> + parse_str_as_multibyte ((const unsigned char *) str, \
>> + size, &nchars, &nbytes); \
>> + s = alloca (sizeof *s + nbytes + 1); \
>> + s->data = (unsigned char *) s + sizeof (*s); \
>> + memcpy (s->data, str, nbytes); \
>> + s->data[size] = '\0'; \
>> + s->intervals = NULL; \
>> + if (nbytes == nchars || nbytes != size) \
>> + s->size = size, s->size_byte = -1; \
>> + else \
>> + s->size = nchars, s->size_byte = nbytes; \
>> + XSETSTRING (string, s); string; })
>
> This will eventually fail with USE_LSB_TAG, since you don't enforce
> alignment.
What about alignment guaranteed by alloca? IIUC compilers tends
to align it enough to US_LSB_TAG:
http://msdn.microsoft.com/en-us/library/x9sx5da1.aspx
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55945
Dmitry
next prev parent reply other threads:[~2014-09-02 13:47 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 12:55 [RFC] temporary Lisp_Strings Dmitry Antipov
2014-09-02 13:21 ` Andreas Schwab
2014-09-02 13:47 ` Dmitry Antipov [this message]
2014-09-02 14:14 ` Andreas Schwab
2014-09-02 15:00 ` Eli Zaretskii
2014-09-02 14:00 ` Stefan Monnier
2014-09-02 15:13 ` Dmitry Antipov
2014-09-02 17:32 ` Stefan Monnier
2014-09-03 10:23 ` Benchmarking temporary Lisp objects [Was: Re: [RFC] temporary Lisp_Strings] Dmitry Antipov
2014-09-03 13:14 ` Stefan Monnier
2014-09-03 14:39 ` Paul Eggert
2014-09-03 15:39 ` Dmitry Antipov
2014-09-03 16:42 ` Paul Eggert
2014-09-03 17:47 ` Stefan Monnier
2014-09-03 18:00 ` Paul Eggert
2014-09-04 4:59 ` Dmitry Antipov
2014-09-04 5:13 ` Paul Eggert
2014-09-04 5:51 ` Dmitry Antipov
2014-09-04 6:45 ` Paul Eggert
2014-09-04 13:11 ` Stefan Monnier
2014-09-04 13:37 ` Dmitry Antipov
2014-09-04 14:46 ` Dmitry Antipov
2014-09-04 16:03 ` Paul Eggert
2014-09-05 4:00 ` Dmitry Antipov
2014-09-05 4:24 ` Stefan Monnier
2014-09-05 9:28 ` Dmitry Antipov
2014-09-05 7:15 ` Paul Eggert
2014-09-05 9:16 ` Dmitry Antipov
2014-09-05 14:35 ` Paul Eggert
2014-09-05 15:35 ` Stefan Monnier
2014-09-08 10:33 ` Dmitry Antipov
2014-09-08 12:01 ` Dmitry Antipov
2014-09-08 13:30 ` Stefan Monnier
2014-09-08 12:44 ` Stefan Monnier
2014-09-08 13:30 ` Stefan Monnier
2014-09-02 14:37 ` [RFC] temporary Lisp_Strings Paul Eggert
2014-09-02 15:24 ` Dmitry Antipov
2014-09-02 15:28 ` Dmitry Antipov
-- strict thread matches above, loose matches on Subject: below --
2014-09-02 12:56 Dmitry Antipov
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