haskell:
Thank you very much for the error report. I have tracked down the cause.
You are searching against an empty Bytestring. This is now represented by
-- | /O(1)/ The empty 'ByteString' empty :: ByteString empty = PS nullForeignPtr 0 0
And while the useAsCString and useAsCStringLen functions never reveal the null pointer, the current library uses unsafeUseAsCStringLen, which returns the null pointer.
And this is getting caught by a null pointer check resulting in your crash. I will post a fix later tonight, and announce it.
Right, empty bytestrings are represented as a nullPtr and a 0 length field. When you use unsafeUseAs* operations, this pointer is passed to a C function as is, without copying. The side condition is that the C function should accept NULL as a 0-length string, which the pcre code evidently doesn't, so its unsafe to use unsafeUseAsCStringLen here, I'll add some more explanatory text about the side conditions that need to hold for this use to be safe, and advise not using unsafe things :) -- Don