2014-09-29 18:45:37 +02:00
|
|
|
<html>
|
|
|
|
|
<head>
|
|
|
|
|
<title>pcre2limits specification</title>
|
|
|
|
|
</head>
|
|
|
|
|
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
|
|
|
|
|
<h1>pcre2limits man page</h1>
|
|
|
|
|
<p>
|
|
|
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
|
|
|
</p>
|
|
|
|
|
<p>
|
|
|
|
|
This page is part of the PCRE2 HTML documentation. It was generated
|
|
|
|
|
automatically from the original man page. If there is any nonsense in it,
|
|
|
|
|
please consult the man page, in case the conversion went wrong.
|
|
|
|
|
<br>
|
|
|
|
|
<br><b>
|
|
|
|
|
SIZE AND OTHER LIMITATIONS
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
There are some size limitations in PCRE2 but it is hoped that they will never
|
|
|
|
|
in practice be relevant.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
The maximum size of a compiled pattern is approximately 64K code units for the
|
|
|
|
|
8-bit and 16-bit libraries if PCRE2 is compiled with the default internal
|
|
|
|
|
linkage size, which is 2 bytes for these libraries. If you want to process
|
|
|
|
|
regular expressions that are truly enormous, you can compile PCRE2 with an
|
|
|
|
|
internal linkage size of 3 or 4 (when building the 16-bit library, 3 is rounded
|
|
|
|
|
up to 4). See the <b>README</b> file in the source distribution and the
|
|
|
|
|
<a href="pcre2build.html"><b>pcre2build</b></a>
|
|
|
|
|
documentation for details. In these cases the limit is substantially larger.
|
|
|
|
|
However, the speed of execution is slower. In the 32-bit library, the internal
|
|
|
|
|
linkage size is always 4.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2015-12-17 19:44:06 +01:00
|
|
|
The maximum length of a source pattern string is essentially unlimited; it is
|
|
|
|
|
the largest number a PCRE2_SIZE variable can hold. However, the program that
|
2015-11-05 18:33:39 +01:00
|
|
|
calls <b>pcre2_compile()</b> can specify a smaller limit.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2014-11-26 17:51:53 +01:00
|
|
|
The maximum length (in code units) of a subject string is one less than the
|
|
|
|
|
largest number a PCRE2_SIZE variable can hold. PCRE2_SIZE is an unsigned
|
|
|
|
|
integer type, usually defined as size_t. Its maximum value (that is
|
|
|
|
|
~(PCRE2_SIZE)0) is reserved as a special indicator for zero-terminated strings
|
|
|
|
|
and unset offsets.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
Note that when using the traditional matching function, PCRE2 uses recursion to
|
|
|
|
|
handle subpatterns and indefinite repetition. This means that the available
|
|
|
|
|
stack space may limit the size of a subject string that can be processed by
|
|
|
|
|
certain patterns. For a discussion of stack issues, see the
|
|
|
|
|
<a href="pcre2stack.html"><b>pcre2stack</b></a>
|
|
|
|
|
documentation.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2014-09-29 18:45:37 +02:00
|
|
|
All values in repeating quantifiers must be less than 65536.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2015-11-05 18:33:39 +01:00
|
|
|
The maximum length of a lookbehind assertion is 65535 characters.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2014-09-29 18:45:37 +02:00
|
|
|
There is no limit to the number of parenthesized subpatterns, but there can be
|
|
|
|
|
no more than 65535 capturing subpatterns. There is, however, a limit to the
|
|
|
|
|
depth of nesting of parenthesized subpatterns of all kinds. This is imposed in
|
2016-11-22 16:37:02 +01:00
|
|
|
order to limit the amount of system stack used at compile time. The default
|
2017-01-16 18:40:47 +01:00
|
|
|
limit can be specified when PCRE2 is built; the default default is 250. An
|
|
|
|
|
application can change this limit by calling pcre2_set_parens_nest_limit() to
|
2016-11-22 16:37:02 +01:00
|
|
|
set the limit in a compile context.
|
2014-09-29 18:45:37 +02:00
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
The maximum length of name for a named subpattern is 32 code units, and the
|
|
|
|
|
maximum number of named subpatterns is 10000.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb
|
2016-11-22 16:37:02 +01:00
|
|
|
is 255 code units for the 8-bit library and 65535 code units for the 16-bit and
|
|
|
|
|
32-bit libraries.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2017-01-16 18:40:47 +01:00
|
|
|
The maximum length of a string argument to a callout is the largest number a
|
2016-11-22 16:37:02 +01:00
|
|
|
32-bit unsigned integer can hold.
|
2014-09-29 18:45:37 +02:00
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
AUTHOR
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
Philip Hazel
|
|
|
|
|
<br>
|
|
|
|
|
University Computing Service
|
|
|
|
|
<br>
|
2014-11-21 17:45:06 +01:00
|
|
|
Cambridge, England.
|
2014-09-29 18:45:37 +02:00
|
|
|
<br>
|
|
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
REVISION
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
2016-11-22 16:37:02 +01:00
|
|
|
Last updated: 26 October 2016
|
2014-09-29 18:45:37 +02:00
|
|
|
<br>
|
2016-11-22 16:37:02 +01:00
|
|
|
Copyright © 1997-2016 University of Cambridge.
|
2014-09-29 18:45:37 +02:00
|
|
|
<br>
|
|
|
|
|
<p>
|
|
|
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
|
|
|
</p>
|
