deftransform for replace is unsafe

[Raymond Toy]

Consider this function

(defun bad (s)
  (declare (simple-string s))
  (replace s s :start2 100 :end2 105))

After compiling this,

(bad (copy-seq "1234567890"))

Produces a totally bogus result, filling in the first 4 characters of the resulting string with garbage.

The problem is that the deftransform for replace just calls BIT-BASH-COPY without verifying that the start and end indices make sense for the given string. Note that it also doesn't check to see that end >= start, but this gets handled by BIT-BASH-COPY which gets a negative length and signals an error.

[toy.raymond@…]

commit 3be4fc215fa2a4d23dc145e6cfa9519492525bc1 Author: Raymond Toy <toy.raymond@…> Date: Sat Dec 22 12:46:45 2012 -0800

Fix ticket:67

Check that the start and end indices make sense for the given strings. This is important before we start bashing random parts of the string, potentially overwriting other objects.