Forth is kind of weak dealing with value types of unknown size. For example, suppose you're writing a cross-compiler, and an address on the target machine might take one or two cells on the host machine depending on the host bitness. Now suppose you need to accept a (host-machine) cell and a target-machine address (e.g. an opcode and an immediate) and manipulate them a bit. Trivial in C, definitely possible in Forth, but supremely annoying and the elegance kind of falls apart.