https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104965
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |msebor at gcc dot gnu.org
--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
It looks like an escape analysis limitation. With this simpler test case using
different types to rule out aliasing assumptions:
#include <string>
int main()
{
std::basic_string<short> s;
auto p = new int[s.size ()]{ };
char c = 0;
if (s.size())
c = *p;
delete[] p;
return c;
}
pr104965.C:9:9: warning: array subscript 0 is outside array bounds of ‘void
[0]’ [-Warray-bounds]
9 | c = *p;
| ^~
pr104965.C:6:34: note: object of size 0 allocated by ‘operator new []’
6 | auto p = new short[s.size ()]{ };
| ^
One of the stores to the local s escapes its address which is then assumed to
have been clobbered by operator new:
<bb 2> [local count: 1073741824]:
s ={v} {CLOBBER};
MEM[(struct _Alloc_hider *)&s] ={v} {CLOBBER};
MEM[(struct _Alloc_hider *)&s]._M_p = &s.D.33279._M_local_buf;
s._M_string_length = 0;
MEM[(char_type &)&s + 16] = 0;
_5 = operator new [] (0);
<bb 3> [local count: 1073741824]:
_10 = s._M_string_length;
if (_10 != 0)
goto <bb 4>; [50.00%]
else
goto <bb 5>; [50.00%]
<bb 4> [local count: 536870913]:
_1 = MEM[(int *)_5];
c_6 = (char) _1;
