Use panic::set_hook() to abort process

See rationnal here: rust-fuzz/honggfuzz-rs@abe2b4c

closes #134

src/lib.rs

@@ -98,6 +98,11 @@ pub fn fuzz<F>(closure: F) where F: Fn(&[u8]) + std::panic::RefUnwindSafe {
  unsafe{std::ptr::read_volatile(&PERSIST_MARKER)}; // hack used in https://github.com/bluss/bencher for black_box()
  // unsafe { asm!("" : : "r"(&PERSIST_MARKER)) }; // hack used in nightly's back_box(), requires feature asm
 
+ // sets panic hook to abort
+ std::panic::set_hook(Box::new(|_| {
+ std::process::abort();
+ }));
+
  let mut input = vec![];
 
  while unsafe{__afl_persistent_loop(1000)} != 0 {
@@ -107,11 +112,17 @@ pub fn fuzz<F>(closure: F) where F: Fn(&[u8]) + std::panic::RefUnwindSafe {
  return;
  }
 
+ // We still catch unwinding panics just in case the fuzzed code modifies
+ // the panic hook.
+ // If so, the fuzzer will be unable to tell different bugs appart and you will
+ // only be able to find one bug at a time before fixing it to then find a new one.
  let did_panic = std::panic::catch_unwind(|| {
  closure(&input);
  }).is_err();
 
  if did_panic {
+ // hopefully the custom panic hook will be called before and abort the
+ // process before the stack frames are unwinded.
  std::process::abort();
  }
  input.clear();