Re: [BUG][PATCH] emacs23, make bootstrap failed on x86_64 systems

[Dan Kruchinin]

Andreas Schwab wrote:
> Dan Kruchinin <address@hidden> 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.