https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103534
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Yes, the warning does disappear when malloc() and free() are used instead of
operator new and delete. foo() also ends up much better optimized, even at
-O1:
__attribute__((abi_tag ("cxx11")))
struct string foo ()
{
struct string & _7(D);
char * _69;
<bb 2> [local count: 1073741824]:
_69 = __builtin_malloc (17);
__builtin_memcpy (_69, "1234567890123456", 16);
MEM[(char_type &)_69 + 16] = 0;
MEM[(struct basic_string *)_7(D)]._M_dataplus._M_p = _69;
MEM[(struct basic_string *)_7(D)].D.33183._M_allocated_capacity = 16;
MEM[(struct basic_string *)_7(D)]._M_string_length = 16;
return _7(D);
}
The -O1 dump in comment #1 doesn't look right, I may have messed something up.
The same issue happens at -O2 where the dump is as follows:
=========== BB 3 ============
Imports: n_5(D)
Exports: _1 n_5(D)
_1 : n_5(D)(I)
n_5(D) int [-INF, -1][1, +INF]
<bb 3> [local count: 536870913]:
_1 = (sizetype) n_5(D);
if (_1 == 1)
goto <bb 4>; [51.12%]
else
goto <bb 5>; [48.88%]
_1 : sizetype [1, 2147483647][18446744071562067968, +INF]
3->4 (T) _1 : sizetype [1, 1]
3->4 (T) n_5(D) : int [1, 1]
3->5 (F) _1 : sizetype [2, 2147483647][18446744071562067968, +INF]
3->5 (F) n_5(D) : int [-INF, -1][2, +INF]
=========== BB 4 ============
<bb 4> [local count: 274448412]:
MEM[(char *)&b] = 0;
goto <bb 6>; [100.00%]
=========== BB 5 ============
<bb 5> [local count: 262422500]:
__builtin_memcpy (&b, &a, _1);
