http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60600
--- Comment #5 from lucdanton at free dot fr --- (In reply to Martin Jambor from comment #2) > Well, this is ICE on code with undefined behavior. Function test > calls itself with a parameter which is a reference to an object of > type child2 and then static_casts it to a reference to child1. These > are non-PODs, neither of these types is an ancestor of the other and > thus the use of static_cast is not allowed by the C++ standard. > […] I must apologise for the peculiar testcase I produced. I normally try to write a sensible program or fragment, but in this case I couldn’t figure out where the problematic behaviour was. In the end I resigned myself to (almost mechanically) discard bits and bits of the original TU until I was left with those things that triggered the ICE and nothing else. (I can’t help but notice that if the testcase is made a complete program by e.g. adding an empty main then strictly speaking there is no UB as control flow never reaches the invalid cast — with the ICE still happening.) For the record, and as best as I can tell, the original code was carefully performing the downcasts inside a (type)case, with no overlap or fallthrough. And if I do apply the patch you supplied, GCC does compile the library without issue.
