To be perfectly pedantic, if `alloca` returns null then the appropriate exception should be something like `AllocaError` (rather plain `Error` to be realistic), as it has no defined cross-platform meaning. However, it's likely that the platforms that do return null from `alloca` mean it to be OOM, so calling `core.exception.onOutOfMemoryError` might be the right move, even though in certain programs it might result in misguided attempts at freeing heap memory then retrying, which may or may not run out of stack space *again*.