[Bug tree-optimization/21407] [4.1 Regression] wrong code with upcast in C++
giovannibajo at libero dot it
gcc-bugzilla@gcc.gnu.org
Tue May 10 15:49:00 GMT 2005
------- Additional Comments From giovannibajo at libero dot it 2005-05-10 15:48 -------
In my example, B is a (sort-of) derived class and A is a (sort-of) base class.
The C++ frontend should use a subobject at offset 0 to represent the base
class. When you downcast through dynamic_cast, you are not doing anything
different from what foo2() is doing, when called with &sb.sa (read: base class).
So what am I missing? What's the difference between:
----------------------------------
/* C code */
struct A { int a; };
struct B { struct A sa; int b; }
void foo(struct A* pa)
{
((struct B*)pa)->b = 0;
}
void bar(void)
{
struct B sb;
foo(&sb.sa);
}
----------------------------------
and
----------------------------------
/* C++ code */
struct A { int a; };
struct B : struct A { int b; }
void foo(struct A* pa)
{
static_cast<B*>(pa)->b = 0;
}
void bar(void)
{
struct B sb;
foo(&sb);
}
----------------------------------
?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21407
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