Documentation update.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@1193 2f5784b3-3f2a-0410-8824-cb99058d5e15

1 files changed, 32 insertions, 2 deletions

diff --git a/doc/pcre.3 b/doc/pcre.3
index 6258e42..c95ee6c 100644
--- a/doc/pcre.3
+++ b/doc/pcre.3
@@ -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 @@ are exported when a shared library is built, and in these cases the
 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 @@ two digits 10, at the domain cam.ac.uk.
 .rs
 .sp
 .nf
-Last updated: 29 October 2012
+Last updated: 30 October 2012
 Copyright (c) 1997-2012 University of Cambridge.
 .fi