Why i can't use reinterpret_cast operator for such a cast?
enum Foo { bar, baz };
void foo(Foo)
{
}
int main()
{
// foo(0); // error: invalid conversion from 'int' to 'Foo'
// foo(reinterpret_cast<Foo>(0)); // error: invalid cast from type 'int' to type 'Foo'
foo(static_cast<Foo>(0));
foo((Foo)0);
}
I think that
reinterpret_cast
can be use for all types of casts, because it's force any type casts to another type with all side-effects of this conversion.
That is a common misconception. Conversions which can be performed with reinterpret_cast
are listed explicitly in 5.2.10 of the standard. int
-to-enum
and enum
-to-int
conversions are not in the list:
nullptr_t
to integerenum
to pointernullptr_t
to other pointer typeT1
to a different pointer-to-member of T2
in cases where both T1
and T2
are objects or functionsreinterpret_cast
is typically used to tell the compiler: Hey, I know you think this region of memory is a T
, but I'd like you to interpret it as a U
(where T
and U
are unrelated types).
It is also worth noting that reinterpret_cast
can have effects on the bits:
5.2.10.3
[ Note: The mapping performed by reinterpret_cast might, or might not, produce a representation dif- ferent from the original value. — end note ]
The C-style cast always works, because it included static_cast
in its attempts.