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Make the use of dftables optional, and not the default. Further tidies to 
documentation.

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">C++ SUPPORT</a>
18 <li><a name="TOC3" href="#SEC3">UTF-8 SUPPORT</a>
19 <li><a name="TOC4" href="#SEC4">UNICODE CHARACTER PROPERTY SUPPORT</a>
20 <li><a name="TOC5" href="#SEC5">CODE VALUE OF NEWLINE</a>
21 <li><a name="TOC6" href="#SEC6">BUILDING SHARED AND STATIC LIBRARIES</a>
22 <li><a name="TOC7" href="#SEC7">POSIX MALLOC 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">LIMITING PCRE RESOURCE USAGE</a>
26 <li><a name="TOC11" href="#SEC11">CREATING CHARACTER TABLES AT BUILD TIME</a>
27 <li><a name="TOC12" href="#SEC12">USING EBCDIC CODE</a>
28 <li><a name="TOC13" href="#SEC13">SEE ALSO</a>
29 <li><a name="TOC14" href="#SEC14">AUTHOR</a>
30 <li><a name="TOC15" href="#SEC15">REVISION</a>
31 </ul>
32 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
33 <P>
34 This document describes the optional features of PCRE that can be selected when
35 the library is compiled. They are all selected, or deselected, by providing
36 options to the <b>configure</b> script that is run before the <b>make</b>
37 command. The complete list of options for <b>configure</b> (which includes the
38 standard ones such as the selection of the installation directory) can be
39 obtained by running
40 <pre>
41 ./configure --help
42 </pre>
43 The following sections include descriptions of options whose names begin with
44 --enable or --disable. These settings specify changes to the defaults for the
45 <b>configure</b> command. Because of the way that <b>configure</b> works,
46 --enable and --disable always come in pairs, so the complementary option always
47 exists as well, but as it specifies the default, it is not described.
48 </P>
49 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
50 <P>
51 By default, the <b>configure</b> script will search for a C++ compiler and C++
52 header files. If it finds them, it automatically builds the C++ wrapper library
53 for PCRE. You can disable this by adding
54 <pre>
55 --disable-cpp
56 </pre>
57 to the <b>configure</b> command.
58 </P>
59 <br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
60 <P>
61 To build PCRE with support for UTF-8 character strings, add
62 <pre>
63 --enable-utf8
64 </pre>
65 to the <b>configure</b> command. Of itself, this does not make PCRE treat
66 strings as UTF-8. As well as compiling PCRE with this option, you also have
67 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
68 function.
69 </P>
70 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
71 <P>
72 UTF-8 support allows PCRE to process character values greater than 255 in the
73 strings that it handles. On its own, however, it does not provide any
74 facilities for accessing the properties of such characters. If you want to be
75 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
76 character properties, you must add
77 <pre>
78 --enable-unicode-properties
79 </pre>
80 to the <b>configure</b> command. This implies UTF-8 support, even if you have
81 not explicitly requested it.
82 </P>
83 <P>
84 Including Unicode property support adds around 30K of tables to the PCRE
85 library. Only the general category properties such as <i>Lu</i> and <i>Nd</i> are
86 supported. Details are given in the
87 <a href="pcrepattern.html"><b>pcrepattern</b></a>
88 documentation.
89 </P>
90 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
91 <P>
92 By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
93 of a line. This is the normal newline character on Unix-like systems. You can
94 compile PCRE to use character 13 (carriage return, CR) instead, by adding
95 <pre>
96 --enable-newline-is-cr
97 </pre>
98 to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
99 which explicitly specifies linefeed as the newline character.
100 <br>
101 <br>
102 Alternatively, you can specify that line endings are to be indicated by the two
103 character sequence CRLF. If you want this, add
104 <pre>
105 --enable-newline-is-crlf
106 </pre>
107 to the <b>configure</b> command. There is a fourth option, specified by
108 <pre>
109 --enable-newline-is-any
110 </pre>
111 which causes PCRE to recognize any Unicode newline sequence.
112 </P>
113 <P>
114 Whatever line ending convention is selected when PCRE is built can be
115 overridden when the library functions are called. At build time it is
116 conventional to use the standard for your operating system.
117 </P>
118 <br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
119 <P>
120 The PCRE building process uses <b>libtool</b> to build both shared and static
121 Unix libraries by default. You can suppress one of these by adding one of
122 <pre>
123 --disable-shared
124 --disable-static
125 </pre>
126 to the <b>configure</b> command, as required.
127 </P>
128 <br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
129 <P>
130 When PCRE is called through the POSIX interface (see the
131 <a href="pcreposix.html"><b>pcreposix</b></a>
132 documentation), additional working storage is required for holding the pointers
133 to capturing substrings, because PCRE requires three integers per substring,
134 whereas the POSIX interface provides only two. If the number of expected
135 substrings is small, the wrapper function uses space on the stack, because this
136 is faster than using <b>malloc()</b> for each call. The default threshold above
137 which the stack is no longer used is 10; it can be changed by adding a setting
138 such as
139 <pre>
140 --with-posix-malloc-threshold=20
141 </pre>
142 to the <b>configure</b> command.
143 </P>
144 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
145 <P>
146 Within a compiled pattern, offset values are used to point from one part to
147 another (for example, from an opening parenthesis to an alternation
148 metacharacter). By default, two-byte values are used for these offsets, leading
149 to a maximum size for a compiled pattern of around 64K. This is sufficient to
150 handle all but the most gigantic patterns. Nevertheless, some people do want to
151 process enormous patterns, so it is possible to compile PCRE to use three-byte
152 or four-byte offsets by adding a setting such as
153 <pre>
154 --with-link-size=3
155 </pre>
156 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
157 longer offsets slows down the operation of PCRE because it has to load
158 additional bytes when handling them.
159 </P>
160 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
161 <P>
162 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
163 by making recursive calls to an internal function called <b>match()</b>. In
164 environments where the size of the stack is limited, this can severely limit
165 PCRE's operation. (The Unix environment does not usually suffer from this
166 problem, but it may sometimes be necessary to increase the maximum stack size.
167 There is a discussion in the
168 <a href="pcrestack.html"><b>pcrestack</b></a>
169 documentation.) An alternative approach to recursion that uses memory from the
170 heap to remember data, instead of using recursive function calls, has been
171 implemented to work round the problem of limited stack size. If you want to
172 build a version of PCRE that works this way, add
173 <pre>
174 --disable-stack-for-recursion
175 </pre>
176 to the <b>configure</b> command. With this configuration, PCRE will use the
177 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
178 management functions. Separate functions are provided because the usage is very
179 predictable: the block sizes requested are always the same, and the blocks are
180 always freed in reverse order. A calling program might be able to implement
181 optimized functions that perform better than the standard <b>malloc()</b> and
182 <b>free()</b> functions. PCRE runs noticeably more slowly when built in this
183 way. This option affects only the <b>pcre_exec()</b> function; it is not
184 relevant for the the <b>pcre_dfa_exec()</b> function.
185 </P>
186 <br><a name="SEC10" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
187 <P>
188 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
189 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
190 function. By controlling the maximum number of times this function may be
191 called during a single matching operation, a limit can be placed on the
192 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
193 at run time, as described in the
194 <a href="pcreapi.html"><b>pcreapi</b></a>
195 documentation. The default is 10 million, but this can be changed by adding a
196 setting such as
197 <pre>
198 --with-match-limit=500000
199 </pre>
200 to the <b>configure</b> command. This setting has no effect on the
201 <b>pcre_dfa_exec()</b> matching function.
202 </P>
203 <P>
204 In some environments it is desirable to limit the depth of recursive calls of
205 <b>match()</b> more strictly than the total number of calls, in order to
206 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
207 is specified) that is used. A second limit controls this; it defaults to the
208 value that is set for --with-match-limit, which imposes no additional
209 constraints. However, you can set a lower limit by adding, for example,
210 <pre>
211 --with-match-limit-recursion=10000
212 </pre>
213 to the <b>configure</b> command. This value can also be overridden at run time.
214 </P>
215 <br><a name="SEC11" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
216 <P>
217 PCRE uses fixed tables for processing characters whose code values are less
218 than 256. By default, PCRE is built with a set of tables that are distributed
219 in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes
220 only. If you add
221 <pre>
222 --enable-rebuild-chartables
223 </pre>
224 to the <b>configure</b> command, the distributed tables are no longer used.
225 Instead, a program called <b>dftables</b> is compiled and run. This outputs the
226 source for new set of tables, created in the default locale of your C runtime
227 system. (This method of replacing the tables does not work if you are cross
228 compiling, because <b>dftables</b> is run on the local host. If you need to
229 create alternative tables when cross compiling, you will have to do so "by
230 hand".)
231 </P>
232 <br><a name="SEC12" href="#TOC1">USING EBCDIC CODE</a><br>
233 <P>
234 PCRE assumes by default that it will run in an environment where the character
235 code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
236 compiled to run in an EBCDIC environment by adding
237 <pre>
238 --enable-ebcdic
239 </pre>
240 to the <b>configure</b> command. This setting implies
241 --enable-rebuild-chartables.
242 </P>
243 <br><a name="SEC13" href="#TOC1">SEE ALSO</a><br>
244 <P>
245 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
246 </P>
247 <br><a name="SEC14" href="#TOC1">AUTHOR</a><br>
248 <P>
249 Philip Hazel
250 <br>
251 University Computing Service
252 <br>
253 Cambridge CB2 3QH, England.
254 <br>
255 </P>
256 <br><a name="SEC15" href="#TOC1">REVISION</a><br>
257 <P>
258 Last updated: 20 March 2007
259 <br>
260 Copyright &copy; 1997-2007 University of Cambridge.
261 <br>
262 <p>
263 Return to the <a href="index.html">PCRE index page</a>.
264 </p>

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