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2: <head>
3: <title>pcrelimits specification</title>
4: </head>
5: <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6: <h1>pcrelimits man page</h1>
7: <p>
8: Return to the <a href="index.html">PCRE index page</a>.
9: </p>
10: <p>
11: This page is part of the PCRE HTML documentation. It was generated automatically
12: from the original man page. If there is any nonsense in it, please consult the
13: man page, in case the conversion went wrong.
14: <br>
15: <br><b>
16: SIZE AND OTHER LIMITATIONS
17: </b><br>
18: <P>
19: There are some size limitations in PCRE but it is hoped that they will never in
20: practice be relevant.
21: </P>
22: <P>
23: The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE is
24: compiled with the default internal linkage size of 2. If you want to process
25: regular expressions that are truly enormous, you can compile PCRE with an
26: internal linkage size of 3 or 4 (see the <b>README</b> file in the source
27: distribution and the
28: <a href="pcrebuild.html"><b>pcrebuild</b></a>
29: documentation for details). In these cases the limit is substantially larger.
30: However, the speed of execution is slower.
31: </P>
32: <P>
33: All values in repeating quantifiers must be less than 65536.
34: </P>
35: <P>
36: There is no limit to the number of parenthesized subpatterns, but there can be
37: no more than 65535 capturing subpatterns.
38: </P>
39: <P>
40: There is a limit to the number of forward references to subsequent subpatterns
41: of around 200,000. Repeated forward references with fixed upper limits, for
42: example, (?2){0,100} when subpattern number 2 is to the right, are included in
43: the count. There is no limit to the number of backward references.
44: </P>
45: <P>
46: The maximum length of name for a named subpattern is 32 characters, and the
47: maximum number of named subpatterns is 10000.
48: </P>
49: <P>
50: The maximum length of a subject string is the largest positive number that an
51: integer variable can hold. However, when using the traditional matching
52: function, PCRE uses recursion to handle subpatterns and indefinite repetition.
53: This means that the available stack space may limit the size of a subject
54: string that can be processed by certain patterns. For a discussion of stack
55: issues, see the
56: <a href="pcrestack.html"><b>pcrestack</b></a>
57: documentation.
58: </P>
59: <br><b>
60: AUTHOR
61: </b><br>
62: <P>
63: Philip Hazel
64: <br>
65: University Computing Service
66: <br>
67: Cambridge CB2 3QH, England.
68: <br>
69: </P>
70: <br><b>
71: REVISION
72: </b><br>
73: <P>
74: Last updated: 30 November 2011
75: <br>
76: Copyright © 1997-2011 University of Cambridge.
77: <br>
78: <p>
79: Return to the <a href="index.html">PCRE index page</a>.
80: </p>
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