Revision: 1193
http://vcs.pcre.org/viewvc?view=rev&revision=1193
Author: ph10
Date: 2012-10-30 17:54:19 +0000 (Tue, 30 Oct 2012)
Log Message:
-----------
Documentation update.
Modified Paths:
--------------
code/trunk/doc/pcre.3
Modified: code/trunk/doc/pcre.3
===================================================================
--- code/trunk/doc/pcre.3 2012-10-30 17:26:55 UTC (rev 1192)
+++ code/trunk/doc/pcre.3 2012-10-30 17:54:19 UTC (rev 1193)
@@ -1,4 +1,4 @@
-.TH PCRE 3 "29 October 2012" "PCRE 8.32"
+.TH PCRE 3 "30 October 2012" "PCRE 8.32"
.SH NAME
PCRE - Perl-compatible regular expressions
.SH INTRODUCTION
@@ -107,6 +107,36 @@
undocumented symbols are not exported.
.
.
+.SH "SECURITY CONSIDERATIONS"
+.rs
+.sp
+If you are using PCRE in a non-UTF application that permits users to supply
+arbitrary patterns for compilation, you should be aware of a feature that
+allows users to turn on UTF support from within a pattern, provided that PCRE
+was built with UTF support. For example, an 8-bit pattern that begins with
+"(*UTF8)" turns on UTF-8 mode. This causes both the pattern and any data
+against which it is matched to be checked for UTF-8 validity. If the data
+string is very long, such a check might use sufficiently many resources as to
+cause your application to lose performance.
+.P
+The best way of guarding against this possibility is to use the
+\fBpcre_fullinfo()\fP function to check the compiled pattern's options for UTF.
+.P
+If your application is one that supports UTF, be aware that validity checking
+can take time. If the same data string is to be matched many times, you can use
+the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to
+save redundant checks.
+.P
+Another way that performance can be hit is by running a pattern that has a very
+large search tree against a string that will never match. Nested unlimited
+repeats in a pattern are a common example. PCRE provides some protection
+against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the
+.\" HREF
+\fBpcreapi\fP
+.\"
+page.
+.
+.
.SH "USER DOCUMENTATION"
.rs
.sp
@@ -165,6 +195,6 @@
.rs
.sp
.nf
-Last updated: 29 October 2012
+Last updated: 30 October 2012
Copyright (c) 1997-2012 University of Cambridge.
.fi
