Add missing classof().
Somewhat troublingly, without this implemented, the check inside
isa_impl<> would silently use the parent's `classof()` when determining
whether it was okay to downcast from the parent to the child!
Bug analysis:
A build failure after removing the parent's `classof()` initially
alerted me to the bug, after which a little bit of thinking and reading
of the code identified the root cause.
The compiler could be made to prevent this bug from happening if there
were a way to ensure that in the code
template <typename To, typename From, typename Enabler = void>
struct isa_impl {
static inline bool doit(const From &Val) {
return To::classof(&Val);
}
};
that `To::classof` is actually inside the class `To`, and not in a base
class. I am not aware of a way to check this in C++. If there is a means
to perform that check, please bring it up on the list and this will be
fixed.
There is a high likelihood that there are other instances of this same
bug in the codebase.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165769 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed