It depends on how this is converted into machine level code. In quite a few cases it breaks down into rather ugly hacks, which is what creates the notion that t

It depends on how this is converted into machine level code. In quite a few cases it breaks down into rather ugly hacks, which is what creates the notion that they are "expensive" (and they are in these cases), and concluding from that should only be used sparingly, especially in code which is performance sensitive. With a sane ABI that includes exceptions as part of the daily life, so to speak, it is also possible to shift normal control flow to them without having any (larger) performance impact from it.