The latest update of PCRE to 8.30 produces the following warning in drupals installation:
Warning: preg_match(): Compilation failed: disallowed Unicode code point (>= 0xd800 && <= 0xdfff) at offset 2112 in truncate_utf8() (line 339 of /home/sites/drupal7/includes/unicode.inc).
This is discussed in full here: http://drupal.org/node/1442876
Systems affected so far are Archlinux and FreeBSD. It is possible that more systems will display such warnings once they update PCRE to 8.30
A user has mentioned that this also affects drupal-searches (http://drupal.org/node/1442876#comment-5622720). I haven't tried it yet myself so I cannot tell.
I created a bug-report on Archlinux (https://bugs.archlinux.org/task/28533) but they suggest that this get fixed on the drupal-side.