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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 with the <b>pcre_exec()</b>
117 function. By controlling the maximum number of times this function may be
118 called during a single matching operation, a limit can be placed on the
119 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
120 at run time, as described in the
121 <a href="pcreapi.html"><b>pcreapi</b></a>
122 documentation. The default is 10 million, but this can be changed by adding a
123 setting such as
124 <pre>
125 --with-match-limit=500000
126 </pre>
127 to the <b>configure</b> command. This setting has no effect on the
128 <b>pcre_dfa_exec()</b> matching function.
129 </P>
130 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
131 <P>
132 Within a compiled pattern, offset values are used to point from one part to
133 another (for example, from an opening parenthesis to an alternation
134 metacharacter). By default, two-byte values are used for these offsets, leading
135 to a maximum size for a compiled pattern of around 64K. This is sufficient to
136 handle all but the most gigantic patterns. Nevertheless, some people do want to
137 process enormous patterns, so it is possible to compile PCRE to use three-byte
138 or four-byte offsets by adding a setting such as
139 <pre>
140 --with-link-size=3
141 </pre>
142 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
143 longer offsets slows down the operation of PCRE because it has to load
144 additional bytes when handling them.
145 </P>
146 <P>
147 If you build PCRE with an increased link size, test 2 (and test 5 if you are
148 using UTF-8) will fail. Part of the output of these tests is a representation
149 of the compiled pattern, and this changes with the link size.
150 </P>
151 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
152 <P>
153 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
154 by making recursive calls to an internal function called <b>match()</b>. In
155 environments where the size of the stack is limited, this can severely limit
156 PCRE's operation. (The Unix environment does not usually suffer from this
157 problem.) An alternative approach that uses memory from the heap to remember
158 data, instead of using recursive function calls, has been implemented to work
159 round this problem. If you want to build a version of PCRE that works this way,
160 add
161 <pre>
162 --disable-stack-for-recursion
163 </pre>
164 to the <b>configure</b> command. With this configuration, PCRE will use the
165 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
166 management functions. Separate functions are provided because the usage is very
167 predictable: the block sizes requested are always the same, and the blocks are
168 always freed in reverse order. A calling program might be able to implement
169 optimized functions that perform better than the standard <b>malloc()</b> and
170 <b>free()</b> functions. PCRE runs noticeably more slowly when built in this
171 way. This option affects only the <b>pcre_exec()</b> function; it is not
172 relevant for the the <b>pcre_dfa_exec()</b> function.
173 </P>
174 <br><a name="SEC10" href="#TOC1">USING EBCDIC CODE</a><br>
175 <P>
176 PCRE assumes by default that it will run in an environment where the character
177 code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
178 compiled to run in an EBCDIC environment by adding
179 <pre>
180 --enable-ebcdic
181 </pre>
182 to the <b>configure</b> command.
183 </P>
184 <P>
185 Last updated: 28 February 2005
186 <br>
187 Copyright &copy; 1997-2005 University of Cambridge.
188 <p>
189 Return to the <a href="index.html">PCRE index page</a>.
190 </p>

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