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pcre 8.34

    1: .TH PCRELIMITS 3 "05 November 2013" "PCRE 8.34"
    2: .SH NAME
    3: PCRE - Perl-compatible regular expressions
    4: .SH "SIZE AND OTHER LIMITATIONS"
    5: .rs
    6: .sp
    7: There are some size limitations in PCRE but it is hoped that they will never in
    8: practice be relevant.
    9: .P
   10: The maximum length of a compiled pattern is approximately 64K data units (bytes
   11: for the 8-bit library, 16-bit units for the 16-bit library, and 32-bit units for
   12: the 32-bit library) if PCRE is compiled with the default internal linkage size,
   13: which is 2 bytes for the 8-bit and 16-bit libraries, and 4 bytes for the 32-bit
   14: library. If you want to process regular expressions that are truly enormous,
   15: you can compile PCRE with an internal linkage size of 3 or 4 (when building the
   16: 16-bit or 32-bit library, 3 is rounded up to 4). See the \fBREADME\fP file in
   17: the source distribution and the
   18: .\" HREF
   19: \fBpcrebuild\fP
   20: .\"
   21: documentation for details. In these cases the limit is substantially larger.
   22: However, the speed of execution is slower.
   23: .P
   24: All values in repeating quantifiers must be less than 65536.
   25: .P
   26: There is no limit to the number of parenthesized subpatterns, but there can be
   27: no more than 65535 capturing subpatterns. There is, however, a limit to the
   28: depth of nesting of parenthesized subpatterns of all kinds. This is imposed in
   29: order to limit the amount of system stack used at compile time. The limit can
   30: be specified when PCRE is built; the default is 250.
   31: .P
   32: There is a limit to the number of forward references to subsequent subpatterns
   33: of around 200,000. Repeated forward references with fixed upper limits, for
   34: example, (?2){0,100} when subpattern number 2 is to the right, are included in
   35: the count. There is no limit to the number of backward references.
   36: .P
   37: The maximum length of name for a named subpattern is 32 characters, and the
   38: maximum number of named subpatterns is 10000.
   39: .P
   40: The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb
   41: is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit libraries.
   42: .P
   43: The maximum length of a subject string is the largest positive number that an
   44: integer variable can hold. However, when using the traditional matching
   45: function, PCRE uses recursion to handle subpatterns and indefinite repetition.
   46: This means that the available stack space may limit the size of a subject
   47: string that can be processed by certain patterns. For a discussion of stack
   48: issues, see the
   49: .\" HREF
   50: \fBpcrestack\fP
   51: .\"
   52: documentation.
   53: .
   54: .
   55: .SH AUTHOR
   56: .rs
   57: .sp
   58: .nf
   59: Philip Hazel
   60: University Computing Service
   61: Cambridge CB2 3QH, England.
   62: .fi
   63: .
   64: .
   65: .SH REVISION
   66: .rs
   67: .sp
   68: .nf
   69: Last updated: 05 November 2013
   70: Copyright (c) 1997-2013 University of Cambridge.
   71: .fi