https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80899
Bug ID: 80899
Summary: Devirtualization causes incorrect code generation with
placement new in some cases
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
From https://bugs.linaro.org/show_bug.cgi?id=2957:
Take:
#include <new>
struct base {
virtual void f() =0;
};
template<typename T> struct foo: base
{
virtual void f() { if (sizeof(T) != sizeof(int)) __builtin_abort(); }
};
template<typename T> struct bar
{
void set() { val = new (&mem) foo<T> (); }
void doit() { val->f(); }
foo<long long> mem;
base *val;
};
int main()
{
bar<int> b;
b.set();
b.doit();
return 0;
}
--- CUT ---
This code should not abort as the dynamic type of val is foo<int> due to the
placement new in the call in set. But currently aborts at -O2 and above due to
the devirtualization deciding the type is statically known as foo<long long>.
