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Load pcre-4.0 into code/trunk.
1 .TH PCRE 3
2 .SH NAME
3 PCRE - Perl-compatible regular expressions
4 .SH PCRE BUILD-TIME OPTIONS
5 .rs
6 .sp
7 This document describes the optional features of PCRE that can be selected when
8 the library is compiled. They are all selected, or deselected, by providing
9 options to the \fBconfigure\fR script which is run before the \fBmake\fR
10 command. The complete list of options for \fBconfigure\fR (which includes the
11 standard ones such as the selection of the installation directory) can be
12 obtained by running
13
14 ./configure --help
15
16 The following sections describe certain options whose names begin with --enable
17 or --disable. These settings specify changes to the defaults for the
18 \fBconfigure\fR command. Because of the way that \fBconfigure\fR works,
19 --enable and --disable always come in pairs, so the complementary option always
20 exists as well, but as it specifies the default, it is not described.
21
22 .SH UTF-8 SUPPORT
23 .rs
24 .sp
25 To build PCRE with support for UTF-8 character strings, add
26
27 --enable-utf8
28
29 to the \fBconfigure\fR command. Of itself, this does not make PCRE treat
30 strings as UTF-8. As well as compiling PCRE with this option, you also have
31 have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fR
32 function.
33
34 .SH CODE VALUE OF NEWLINE
35 .rs
36 .sp
37 By default, PCRE treats character 10 (linefeed) as the newline character. This
38 is the normal newline character on Unix-like systems. You can compile PCRE to
39 use character 13 (carriage return) instead by adding
40
41 --enable-newline-is-cr
42
43 to the \fBconfigure\fR command. For completeness there is also a
44 --enable-newline-is-lf option, which explicitly specifies linefeed as the
45 newline character.
46
47 .SH BUILDING SHARED AND STATIC LIBRARIES
48 .rs
49 .sp
50 The PCRE building process uses \fBlibtool\fR to build both shared and static
51 Unix libraries by default. You can suppress one of these by adding one of
52
53 --disable-shared
54 --disable-static
55
56 to the \fBconfigure\fR command, as required.
57
58 .SH POSIX MALLOC USAGE
59 .rs
60 .sp
61 When PCRE is called through the POSIX interface (see the \fBpcreposix\fR
62 documentation), additional working storage is required for holding the pointers
63 to capturing substrings because PCRE requires three integers per substring,
64 whereas the POSIX interface provides only two. If the number of expected
65 substrings is small, the wrapper function uses space on the stack, because this
66 is faster than using \fBmalloc()\fR for each call. The default threshold above
67 which the stack is no longer used is 10; it can be changed by adding a setting
68 such as
69
70 --with-posix-malloc-threshold=20
71
72 to the \fBconfigure\fR command.
73
74 .SH LIMITING PCRE RESOURCE USAGE
75 .rs
76 .sp
77 Internally, PCRE has a function called \fBmatch()\fR which it calls repeatedly
78 (possibly recursively) when performing a matching operation. By limiting the
79 number of times this function may be called, a limit can be placed on the
80 resources used by a single call to \fBpcre_exec()\fR. The limit can be changed
81 at run time, as described in the \fBpcreapi\fR documentation. The default is 10
82 million, but this can be changed by adding a setting such as
83
84 --with-match-limit=500000
85
86 to the \fBconfigure\fR command.
87
88 .SH HANDLING VERY LARGE PATTERNS
89 .rs
90 .sp
91 Within a compiled pattern, offset values are used to point from one part to
92 another (for example, from an opening parenthesis to an alternation
93 metacharacter). By default two-byte values are used for these offsets, leading
94 to a maximum size for a compiled pattern of around 64K. This is sufficient to
95 handle all but the most gigantic patterns. Nevertheless, some people do want to
96 process enormous patterns, so it is possible to compile PCRE to use three-byte
97 or four-byte offsets by adding a setting such as
98
99 --with-link-size=3
100
101 to the \fBconfigure\fR command. The value given must be 2, 3, or 4. Using
102 longer offsets slows down the operation of PCRE because it has to load
103 additional bytes when handling them.
104
105 If you build PCRE with an increased link size, test 2 (and test 5 if you are
106 using UTF-8) will fail. Part of the output of these tests is a representation
107 of the compiled pattern, and this changes with the link size.
108
109 .in 0
110 Last updated: 21 January 2003
111 .br
112 Copyright (c) 1997-2003 University of Cambridge.

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