LLVM has it's own hand rolled alternative to RTTI that is a speed improvement over built-in RTTI and allows dynamic casting to classes with no vtable (dyn_cast
). However, it can still be used in exactly the way that dynamic_cast<>
is used though it does allow it to be used with more classes.
dyn_cast<>
template documentation
LLVM is a reputable C++ project so this seems to fly in the face of the common saying that too many dynamic casts is a sign of bad design, also known as a code smell. Surely a better performing dynamic cast does nothing to improve its use in design than a standard dynamic_cast
. So who is right here? Are there cases where large-scale use of dynamic casting is a good design choice in C++ code? Google turns up 690 occurrences of this kind of dynamic casting in the LLVM trunk source code.