On 09/17/2014 06:15 PM, Andy Falanga (afalanga) wrote:
> Ha, nothing except my thinking that, because I was casting a
> reference, I had to use reinterpret_cast<>. Of course, that (your
> suggestion) worked for me. Please point me to the correct section
> of the language spec so that I might better understand why this is
> undefined behavior.
Here's the C version:
"6.5 Expressions":
An object shall have its stored value accessed only by an lvalue
expression that has one of the following types:
a type compatible with the effective type of the object,
a qualified version of a type compatible with the effective type
of the object,
a type that is the signed or unsigned type corresponding to the
effective type of the object,
a type that is the signed or unsigned type corresponding to a
qualified version of the effective type of the object,
an aggregate or union type that includes one of the aforementioned
types among its members (including, recursively, a member of a
subaggregate or contained union), or
a character type.
C++ uses the same rule. If you access an object using an lvalue
expression of an incompatible type, all bets are off.
static_cast<Flag>(reinterpret_cast<unsigned int&>(f1) is an example
of such an expression.
Andrew.
