"David Roundy"
I just want to point out that unsafePerformIO is at the core of the (safe) bytestring library. As SPJ et al pointed out, this is crucial functionality, and is only unsafe if unsafely used.
In Modula-3 modules using hacks must be explicitly marked as UNSAFE. See http://www.cs.purdue.edu/homes/hosking/m3/reference/unsafe.html Maybe this is also an option for Haskell?
I don't think this is a good idea.
I think the point is (should be) to mark functions unsafe when they may be unsafe to /use/, and not when they just make use of potentially unsafe functionality. It is perfectly reasonable to write safe (pure) code that uses unsafe ones. You just have to trust the author to get it right.
I'd be curious as to how much of the Prelude would be marked unsafe if you had your wish...
All of it? In the end it is all passed to GCC (or generates assembly), which is inherently "unsafe". :-) -k -- If I haven't seen further, it is by standing in the footprints of giants