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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 <h1>pcrebuild man page</h1>
7 <p>
8 Return to the <a href="index.html">PCRE index page</a>.
9 </p>
10 <p>
11 This page is part of the PCRE HTML documentation. It was generated automatically
12 from the original man page. If there is any nonsense in it, please consult the
13 man page, in case the conversion went wrong.
14 <br>
15 <ul>
16 <li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a>
17 <li><a name="TOC2" href="#SEC2">UTF-8 SUPPORT</a>
19 <li><a name="TOC4" href="#SEC4">CODE VALUE OF NEWLINE</a>
21 <li><a name="TOC6" href="#SEC6">POSIX MALLOC USAGE</a>
22 <li><a name="TOC7" href="#SEC7">LIMITING PCRE RESOURCE USAGE</a>
23 <li><a name="TOC8" href="#SEC8">HANDLING VERY LARGE PATTERNS</a>
24 <li><a name="TOC9" href="#SEC9">AVOIDING EXCESSIVE STACK USAGE</a>
25 <li><a name="TOC10" href="#SEC10">USING EBCDIC CODE</a>
26 </ul>
27 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
28 <P>
29 This document describes the optional features of PCRE that can be selected when
30 the library is compiled. They are all selected, or deselected, by providing
31 options to the <b>configure</b> script that is run before the <b>make</b>
32 command. The complete list of options for <b>configure</b> (which includes the
33 standard ones such as the selection of the installation directory) can be
34 obtained by running
35 <pre>
36 ./configure --help
37 </pre>
38 The following sections describe certain options whose names begin with --enable
39 or --disable. These settings specify changes to the defaults for the
40 <b>configure</b> command. Because of the way that <b>configure</b> works,
41 --enable and --disable always come in pairs, so the complementary option always
42 exists as well, but as it specifies the default, it is not described.
43 </P>
44 <br><a name="SEC2" href="#TOC1">UTF-8 SUPPORT</a><br>
45 <P>
46 To build PCRE with support for UTF-8 character strings, add
47 <pre>
48 --enable-utf8
49 </pre>
50 to the <b>configure</b> command. Of itself, this does not make PCRE treat
51 strings as UTF-8. As well as compiling PCRE with this option, you also have
52 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
53 function.
54 </P>
55 <br><a name="SEC3" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
56 <P>
57 UTF-8 support allows PCRE to process character values greater than 255 in the
58 strings that it handles. On its own, however, it does not provide any
59 facilities for accessing the properties of such characters. If you want to be
60 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
61 character properties, you must add
62 <pre>
63 --enable-unicode-properties
64 </pre>
65 to the <b>configure</b> command. This implies UTF-8 support, even if you have
66 not explicitly requested it.
67 </P>
68 <P>
69 Including Unicode property support adds around 90K of tables to the PCRE
70 library, approximately doubling its size. Only the general category properties
71 such as <i>Lu</i> and <i>Nd</i> are supported. Details are given in the
72 <a href="pcrepattern.html"><b>pcrepattern</b></a>
73 documentation.
74 </P>
75 <br><a name="SEC4" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
76 <P>
77 By default, PCRE treats character 10 (linefeed) as the newline character. This
78 is the normal newline character on Unix-like systems. You can compile PCRE to
79 use character 13 (carriage return) instead by adding
80 <pre>
81 --enable-newline-is-cr
82 </pre>
83 to the <b>configure</b> command. For completeness there is also a
84 --enable-newline-is-lf option, which explicitly specifies linefeed as the
85 newline character.
86 </P>
87 <br><a name="SEC5" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
88 <P>
89 The PCRE building process uses <b>libtool</b> to build both shared and static
90 Unix libraries by default. You can suppress one of these by adding one of
91 <pre>
92 --disable-shared
93 --disable-static
94 </pre>
95 to the <b>configure</b> command, as required.
96 </P>
97 <br><a name="SEC6" href="#TOC1">POSIX MALLOC USAGE</a><br>
98 <P>
99 When PCRE is called through the POSIX interface (see the
100 <a href="pcreposix.html"><b>pcreposix</b></a>
101 documentation), additional working storage is required for holding the pointers
102 to capturing substrings, because PCRE requires three integers per substring,
103 whereas the POSIX interface provides only two. If the number of expected
104 substrings is small, the wrapper function uses space on the stack, because this
105 is faster than using <b>malloc()</b> for each call. The default threshold above
106 which the stack is no longer used is 10; it can be changed by adding a setting
107 such as
108 <pre>
109 --with-posix-malloc-threshold=20
110 </pre>
111 to the <b>configure</b> command.
112 </P>
113 <br><a name="SEC7" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
114 <P>
115 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
116 (possibly recursively) when matching a pattern. By controlling the maximum
117 number of times this function may be called during a single matching operation,
118 a limit can be placed on the resources used by a single call to
119 <b>pcre_exec()</b>. The limit can be changed at run time, as described in the
120 <a href="pcreapi.html"><b>pcreapi</b></a>
121 documentation. The default is 10 million, but this can be changed by adding a
122 setting such as
123 <pre>
124 --with-match-limit=500000
125 </pre>
126 to the <b>configure</b> command.
127 </P>
128 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
129 <P>
130 Within a compiled pattern, offset values are used to point from one part to
131 another (for example, from an opening parenthesis to an alternation
132 metacharacter). By default, two-byte values are used for these offsets, leading
133 to a maximum size for a compiled pattern of around 64K. This is sufficient to
134 handle all but the most gigantic patterns. Nevertheless, some people do want to
135 process enormous patterns, so it is possible to compile PCRE to use three-byte
136 or four-byte offsets by adding a setting such as
137 <pre>
138 --with-link-size=3
139 </pre>
140 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
141 longer offsets slows down the operation of PCRE because it has to load
142 additional bytes when handling them.
143 </P>
144 <P>
145 If you build PCRE with an increased link size, test 2 (and test 5 if you are
146 using UTF-8) will fail. Part of the output of these tests is a representation
147 of the compiled pattern, and this changes with the link size.
148 </P>
149 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
150 <P>
151 PCRE implements backtracking while matching by making recursive calls to an
152 internal function called <b>match()</b>. In environments where the size of the
153 stack is limited, this can severely limit PCRE's operation. (The Unix
154 environment does not usually suffer from this problem.) An alternative approach
155 that uses memory from the heap to remember data, instead of using recursive
156 function calls, has been implemented to work round this problem. If you want to
157 build a version of PCRE that works this way, add
158 <pre>
159 --disable-stack-for-recursion
160 </pre>
161 to the <b>configure</b> command. With this configuration, PCRE will use the
162 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
163 management functions. Separate functions are provided because the usage is very
164 predictable: the block sizes requested are always the same, and the blocks are
165 always freed in reverse order. A calling program might be able to implement
166 optimized functions that perform better than the standard <b>malloc()</b> and
167 <b>free()</b> functions. PCRE runs noticeably more slowly when built in this
168 way.
169 </P>
170 <br><a name="SEC10" href="#TOC1">USING EBCDIC CODE</a><br>
171 <P>
172 PCRE assumes by default that it will run in an environment where the character
173 code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
174 compiled to run in an EBCDIC environment by adding
175 <pre>
176 --enable-ebcdic
177 </pre>
178 to the <b>configure</b> command.
179 </P>
180 <P>
181 Last updated: 09 September 2004
182 <br>
183 Copyright &copy; 1997-2004 University of Cambridge.
184 <p>
185 Return to the <a href="index.html">PCRE index page</a>.
186 </p>

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