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1.1.1.5 ! misho       1: .TH PCRELIMITS 3 "05 November 2013" "PCRE 8.34"
1.1       misho       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
1.1.1.2   misho      10: The maximum length of a compiled pattern is approximately 64K data units (bytes
1.1.1.5 ! misho      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,
1.1.1.4   misho      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
1.1       misho      18: .\" HREF
                     19: \fBpcrebuild\fP
                     20: .\"
1.1.1.2   misho      21: documentation for details. In these cases the limit is substantially larger.
1.1       misho      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
1.1.1.5 ! misho      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.
1.1       misho      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
1.1.1.3   misho      40: The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb
1.1.1.5 ! misho      41: is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit libraries.
1.1.1.3   misho      42: .P
1.1       misho      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
1.1.1.5 ! misho      69: Last updated: 05 November 2013
        !            70: Copyright (c) 1997-2013 University of Cambridge.
1.1       misho      71: .fi