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1 <html>
2 <head>
3 <title>pcrebuild specification</title>
4 </head>
5 <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 This HTML document has been generated automatically from the original man page.
7 If there is any nonsense in it, please consult the man page, in case the
8 conversion went wrong.<br>
9 <ul>
10 <li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a>
11 <li><a name="TOC2" href="#SEC2">UTF-8 SUPPORT</a>
12 <li><a name="TOC3" href="#SEC3">CODE VALUE OF NEWLINE</a>
13 <li><a name="TOC4" href="#SEC4">BUILDING SHARED AND STATIC LIBRARIES</a>
14 <li><a name="TOC5" href="#SEC5">POSIX MALLOC USAGE</a>
15 <li><a name="TOC6" href="#SEC6">LIMITING PCRE RESOURCE USAGE</a>
16 <li><a name="TOC7" href="#SEC7">HANDLING VERY LARGE PATTERNS</a>
17 </ul>
18 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
19 <P>
20 This document describes the optional features of PCRE that can be selected when
21 the library is compiled. They are all selected, or deselected, by providing
22 options to the <b>configure</b> script which is run before the <b>make</b>
23 command. The complete list of options for <b>configure</b> (which includes the
24 standard ones such as the selection of the installation directory) can be
25 obtained by running
26 </P>
27 <P>
28 <pre>
29 ./configure --help
30 </PRE>
31 </P>
32 <P>
33 The following sections describe certain options whose names begin with --enable
34 or --disable. These settings specify changes to the defaults for the
35 <b>configure</b> command. Because of the way that <b>configure</b> works,
36 --enable and --disable always come in pairs, so the complementary option always
37 exists as well, but as it specifies the default, it is not described.
38 </P>
39 <br><a name="SEC2" href="#TOC1">UTF-8 SUPPORT</a><br>
40 <P>
41 To build PCRE with support for UTF-8 character strings, add
42 </P>
43 <P>
44 <pre>
45 --enable-utf8
46 </PRE>
47 </P>
48 <P>
49 to the <b>configure</b> command. Of itself, this does not make PCRE treat
50 strings as UTF-8. As well as compiling PCRE with this option, you also have
51 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
52 function.
53 </P>
54 <br><a name="SEC3" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
55 <P>
56 By default, PCRE treats character 10 (linefeed) as the newline character. This
57 is the normal newline character on Unix-like systems. You can compile PCRE to
58 use character 13 (carriage return) instead by adding
59 </P>
60 <P>
61 <pre>
62 --enable-newline-is-cr
63 </PRE>
64 </P>
65 <P>
66 to the <b>configure</b> command. For completeness there is also a
67 --enable-newline-is-lf option, which explicitly specifies linefeed as the
68 newline character.
69 </P>
70 <br><a name="SEC4" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
71 <P>
72 The PCRE building process uses <b>libtool</b> to build both shared and static
73 Unix libraries by default. You can suppress one of these by adding one of
74 </P>
75 <P>
76 <pre>
77 --disable-shared
78 --disable-static
79 </PRE>
80 </P>
81 <P>
82 to the <b>configure</b> command, as required.
83 </P>
84 <br><a name="SEC5" href="#TOC1">POSIX MALLOC USAGE</a><br>
85 <P>
86 When PCRE is called through the POSIX interface (see the <b>pcreposix</b>
87 documentation), additional working storage is required for holding the pointers
88 to capturing substrings because PCRE requires three integers per substring,
89 whereas the POSIX interface provides only two. If the number of expected
90 substrings is small, the wrapper function uses space on the stack, because this
91 is faster than using <b>malloc()</b> for each call. The default threshold above
92 which the stack is no longer used is 10; it can be changed by adding a setting
93 such as
94 </P>
95 <P>
96 <pre>
97 --with-posix-malloc-threshold=20
98 </PRE>
99 </P>
100 <P>
101 to the <b>configure</b> command.
102 </P>
103 <br><a name="SEC6" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
104 <P>
105 Internally, PCRE has a function called <b>match()</b> which it calls repeatedly
106 (possibly recursively) when performing a matching operation. By limiting the
107 number of times this function may be called, a limit can be placed on the
108 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
109 at run time, as described in the <b>pcreapi</b> documentation. The default is 10
110 million, but this can be changed by adding a setting such as
111 </P>
112 <P>
113 <pre>
114 --with-match-limit=500000
115 </PRE>
116 </P>
117 <P>
118 to the <b>configure</b> command.
119 </P>
120 <br><a name="SEC7" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
121 <P>
122 Within a compiled pattern, offset values are used to point from one part to
123 another (for example, from an opening parenthesis to an alternation
124 metacharacter). By default two-byte values are used for these offsets, leading
125 to a maximum size for a compiled pattern of around 64K. This is sufficient to
126 handle all but the most gigantic patterns. Nevertheless, some people do want to
127 process enormous patterns, so it is possible to compile PCRE to use three-byte
128 or four-byte offsets by adding a setting such as
129 </P>
130 <P>
131 <pre>
132 --with-link-size=3
133 </PRE>
134 </P>
135 <P>
136 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
137 longer offsets slows down the operation of PCRE because it has to load
138 additional bytes when handling them.
139 </P>
140 <P>
141 If you build PCRE with an increased link size, test 2 (and test 5 if you are
142 using UTF-8) will fail. Part of the output of these tests is a representation
143 of the compiled pattern, and this changes with the link size.
144 </P>
145 <P>
146 Last updated: 21 January 2003
147 <br>
148 Copyright &copy; 1997-2003 University of Cambridge.

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