https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102690
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-10-12
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Oh, I can probably fix the
FAIL: g++.dg/warn/Warray-bounds-16.C -std=gnu++17 scan-tree-dump-not
optimized "goto"
since the expected optimization is not valid. But the IMHO bogus excess error
remains, see PR101480 for an analysis. Quote:
--
What we see is the global variable construction function which accesses
just 'a', and yes, the call to 'new' is considered clobbering global
variables (including 'a'):
<bb 2> [local count: 1073741824]:
MEM[(struct __as_base &)&a] ={v} {CLOBBER};
a.m = 0;
_5 = operator new [] (0);
a.p = _5;
goto <bb 4>; [100.00%]
<bb 3> [local count: 8687547547]:
_7 = (long unsigned int) i_6;
_8 = _7 * 4;
_9 = _5 + _8;
MEM[(int *)_9] = 0;
i_10 = i_6 + 1;
<bb 4> [local count: 9761289362]:
# i_6 = PHI <0(2), i_10(3)>
_11 = a.m;
if (i_6 < _11)
goto <bb 3>; [89.00%]
else
goto <bb 5>; [11.00%]
<bb 5> [local count: 1073741824]:
return;
I suppose implementing the global operator new as accessing a.m would
be valid as IIRC lifetime of a starts when the CTOR is invoked, not
when it finished (otherwise the CTOR could not access the variable itself).
We somehow conclude that
_9: void * [1B, +INF] EQUIVALENCES: { } (0 elements)
possibly because it cannot be NULL (?):
extract_range_from_stmt visiting:
_5 = operator new [] (0);
Found new range for _5: void * [1B, +INF]
marking stmt to be not simulated again
(huh?)
and then the -Warray-bounds warning concludes the access is always outside
of the allocated area.
I suspect when we'd arrive at VARYING we'd not issue the warning even
when the access would always extend beyond a zero-sized allocation.
--
