From: Dan Kruchinin <dan.kruchinin@gmail.com>
To: Andreas Schwab <schwab@suse.de>
Cc: emacs-devel@gnu.org
Subject: Re: [BUG][PATCH] emacs23, make bootstrap failed on x86_64 systems
Date: Fri, 04 Apr 2008 13:46:18 +0400 [thread overview]
Message-ID: <47F5F8EA.40101@gmail.com> (raw)
In-Reply-To: <je63uym2by.fsf@sykes.suse.de>
Andreas Schwab wrote:
> Dan Kruchinin <dan.kruchinin@gmail.com> writes:
>
>
>> But it'll never return false on _LP64 systems(on which EMACS_INT is long
>> and sizeof(long) == 8),
>> because it uses low bitwise operations expecting that sizeof(EMACS_INT) ==
>> 4:
>>
>> --- src/editfns.c: lisp_time_argument ---
>> *result = (XINT (high) << 16) + (XINT (low) & 0xffff);
>> return *result >> 16 == XINT (high);
>>
>
> Where does this assume a 32bit EMACS_INT?
>
> Andreas.
>
>
I looked more closely at src/editfns.c and how it works with date and
time, so
1st: yep, my patch was invalid
2nd:
All functions use int data type for holding seconds. Here for example
code from current-time
function:
--
EMACS_TIME t;
EMACS_GET_TIME (t);
return list3 (make_number ((EMACS_SECS (t) >> 16) & 0xffff),
make_number ((EMACS_SECS (t) >> 0) & 0xffff),
make_number (EMACS_USECS (t)));
--
or from get-internal-run-time:
--
int secs, usecs;
...
return list3 (make_number ((secs >> 16) & 0xffff),
make_number ((secs >> 0) & 0xffff),
make_number (usecs));
--
It implies that both HIGH and LOW have size = 2 bytes.
It also implies that they are not depend on how big is int: 32 or 64 bits.
But in the function lisp_time_argument 'high' can be greater than 2 bytes
because XINT(high) returns long(8 bytes on _LP64) and
"*result = (XINT (high) << 16) + (XINT (low) & 0xffff)"
will not truncate it because 'result' has type time_t which can be >
than 4 bytes. (8 bytes on _LP64).
Something like this seems to be valid:
"*result = ((XINT (high) & 0xffff) << 16) + (XINT (low) & 0xffff);"
or like this:
"*result &= 0xffffffff;"
Anyway if "seconds" have some size restriction, lisp_time_argument
should check it correctly.
W.B.R.
Dan Kruchinin.
prev parent reply other threads:[~2008-04-04 9:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-04 7:27 [BUG][PATCH] emacs23, make bootstrap failed on x86_64 systems Dan Kruchinin
2008-04-04 8:49 ` Andreas Schwab
2008-04-04 9:46 ` Dan Kruchinin [this message]
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