Eli Zaretskii <
address@hidden> schrieb am So., 17. Sep. 2017 um 16:31 Uhr:
> Cc: address@hidden, address@hidden
> From: Paul Eggert <address@hidden>
> Date: Sun, 17 Sep 2017 00:01:09 -0700
>
> Why was the attached patch needed? What warning did it suppress?
I wrote about that in
http://lists.gnu.org/archive/html/emacs-devel/2017-09/msg00448.html
The warning is this:
../../emacs/src/data.c: In function 'minmax_driver':
../../emacs/src/data.c:3022:9: warning: 'accum.i' may be used uninitialized in this function [-Wmaybe-uninitialized]
return accum;
^~~~~
Which seems to mean that even eassume is sometimes not enough to
convince GCC 7 that the code is correct:
static Lisp_Object
minmax_driver (ptrdiff_t nargs, Lisp_Object *args,
enum Arith_Comparison comparison)
{
eassume (0 < nargs); <<<<<<<<<<<<<<<<<<<<<<<
Lisp_Object accum;
for (ptrdiff_t argnum = 0; argnum < nargs; argnum++)
{
Lisp_Object val = args[argnum];
CHECK_NUMBER_OR_FLOAT_COERCE_MARKER (val);
if (argnum == 0 || !NILP (arithcompare (val, accum, comparison)))
accum = val;
else if (FLOATP (accum) && isnan (XFLOAT_DATA (accum)))
return accum;
}
return accum;
}
Since nargs > 0, the loop is always entered, but GCC seems to miss that.
How about rewriting the function body like this:
{
Lisp_Object accum = args[0];
CHECK_NUMBER_OR_FLOAT_COERCE_MARKER (accum);
for (ptrdiff_t argnum = 1; ...)
{
if (FLOATP (accum) && isnan (...)) break;
...
}
return accum;
}