1PCRELIMITS(3)              Library Functions Manual              PCRELIMITS(3)
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NAME

6       PCRE - Perl-compatible regular expressions
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SIZE AND OTHER LIMITATIONS

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10       There  are some size limitations in PCRE but it is hoped that they will
11       never in practice be relevant.
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13       The maximum length of a compiled  pattern  is  approximately  64K  data
14       units  (bytes  for  the  8-bit  library,  32-bit  units  for the 32-bit
15       library, and 32-bit units for the 32-bit library) if PCRE  is  compiled
16       with  the  default  internal  linkage  size  of 2 bytes. If you want to
17       process regular expressions that are truly enormous,  you  can  compile
18       PCRE  with an internal linkage size of 3 or 4 (when building the 16-bit
19       or 32-bit library, 3 is rounded up to 4). See the README  file  in  the
20       source  distribution  and  the  pcrebuild documentation for details. In
21       these cases the limit is substantially larger.  However, the  speed  of
22       execution is slower.
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24       All values in repeating quantifiers must be less than 65536.
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26       There is no limit to the number of parenthesized subpatterns, but there
27       can be no more than 65535 capturing subpatterns.
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29       There is a limit to the number of forward references to subsequent sub‐
30       patterns  of  around  200,000.  Repeated  forward references with fixed
31       upper limits, for example, (?2){0,100} when subpattern number 2  is  to
32       the  right,  are included in the count. There is no limit to the number
33       of backward references.
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35       The maximum length of name for a named subpattern is 32 characters, and
36       the maximum number of named subpatterns is 10000.
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38       The  maximum  length  of  a  name  in  a (*MARK), (*PRUNE), (*SKIP), or
39       (*THEN) verb is 255 for the 8-bit library and 65535 for the 16-bit  and
40       32-bit library.
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42       The  maximum  length of a subject string is the largest positive number
43       that an integer variable can hold. However, when using the  traditional
44       matching function, PCRE uses recursion to handle subpatterns and indef‐
45       inite repetition.  This means that the available stack space may  limit
46       the size of a subject string that can be processed by certain patterns.
47       For a discussion of stack issues, see the pcrestack documentation.
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AUTHOR

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51       Philip Hazel
52       University Computing Service
53       Cambridge CB2 3QH, England.
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REVISION

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57       Last updated: 04 May 2012
58       Copyright (c) 1997-2012 University of Cambridge.
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62PCRE 8.30                        24 June 2012                    PCRELIMITS(3)