ViewVC logotype

Contents of /code/trunk/doc/html/pcrebuild.html

Parent Directory Parent Directory | Revision Log Revision Log

Revision 261 - (show annotations)
Fri Sep 21 08:37:48 2007 UTC (14 years ago) by ph10
File MIME type: text/html
File size: 12556 byte(s)
Final doc updates and file tidies for 7.4.
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>
20 <li><a name="TOC5" href="#SEC5">CODE VALUE OF NEWLINE</a>
21 <li><a name="TOC6" href="#SEC6">WHAT \R MATCHES</a>
23 <li><a name="TOC8" href="#SEC8">POSIX MALLOC USAGE</a>
24 <li><a name="TOC9" href="#SEC9">HANDLING VERY LARGE PATTERNS</a>
25 <li><a name="TOC10" href="#SEC10">AVOIDING EXCESSIVE STACK USAGE</a>
26 <li><a name="TOC11" href="#SEC11">LIMITING PCRE RESOURCE USAGE</a>
27 <li><a name="TOC12" href="#SEC12">CREATING CHARACTER TABLES AT BUILD TIME</a>
28 <li><a name="TOC13" href="#SEC13">USING EBCDIC CODE</a>
29 <li><a name="TOC14" href="#SEC14">SEE ALSO</a>
30 <li><a name="TOC15" href="#SEC15">AUTHOR</a>
31 <li><a name="TOC16" href="#SEC16">REVISION</a>
32 </ul>
33 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
34 <P>
35 This document describes the optional features of PCRE that can be selected when
36 the library is compiled. It assumes use of the <b>configure</b> script, where
37 the optional features are selected or deselected by providing options to
38 <b>configure</b> before running the <b>make</b> command. However, the same
39 options can be selected in both Unix-like and non-Unix-like environments using
40 the GUI facility of <b>CMakeSetup</b> if you are using <b>CMake</b> instead of
41 <b>configure</b> to build PCRE.
42 </P>
43 <P>
44 The complete list of options for <b>configure</b> (which includes the standard
45 ones such as the selection of the installation directory) can be obtained by
46 running
47 <pre>
48 ./configure --help
49 </pre>
50 The following sections include descriptions of options whose names begin with
51 --enable or --disable. These settings specify changes to the defaults for the
52 <b>configure</b> command. Because of the way that <b>configure</b> works,
53 --enable and --disable always come in pairs, so the complementary option always
54 exists as well, but as it specifies the default, it is not described.
55 </P>
56 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
57 <P>
58 By default, the <b>configure</b> script will search for a C++ compiler and C++
59 header files. If it finds them, it automatically builds the C++ wrapper library
60 for PCRE. You can disable this by adding
61 <pre>
62 --disable-cpp
63 </pre>
64 to the <b>configure</b> command.
65 </P>
66 <br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
67 <P>
68 To build PCRE with support for UTF-8 character strings, add
69 <pre>
70 --enable-utf8
71 </pre>
72 to the <b>configure</b> command. Of itself, this does not make PCRE treat
73 strings as UTF-8. As well as compiling PCRE with this option, you also have
74 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
75 function.
76 </P>
77 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
78 <P>
79 UTF-8 support allows PCRE to process character values greater than 255 in the
80 strings that it handles. On its own, however, it does not provide any
81 facilities for accessing the properties of such characters. If you want to be
82 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
83 character properties, you must add
84 <pre>
85 --enable-unicode-properties
86 </pre>
87 to the <b>configure</b> command. This implies UTF-8 support, even if you have
88 not explicitly requested it.
89 </P>
90 <P>
91 Including Unicode property support adds around 30K of tables to the PCRE
92 library. Only the general category properties such as <i>Lu</i> and <i>Nd</i> are
93 supported. Details are given in the
94 <a href="pcrepattern.html"><b>pcrepattern</b></a>
95 documentation.
96 </P>
97 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
98 <P>
99 By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
100 of a line. This is the normal newline character on Unix-like systems. You can
101 compile PCRE to use character 13 (carriage return, CR) instead, by adding
102 <pre>
103 --enable-newline-is-cr
104 </pre>
105 to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
106 which explicitly specifies linefeed as the newline character.
107 <br>
108 <br>
109 Alternatively, you can specify that line endings are to be indicated by the two
110 character sequence CRLF. If you want this, add
111 <pre>
112 --enable-newline-is-crlf
113 </pre>
114 to the <b>configure</b> command. There is a fourth option, specified by
115 <pre>
116 --enable-newline-is-anycrlf
117 </pre>
118 which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
119 indicating a line ending. Finally, a fifth option, specified by
120 <pre>
121 --enable-newline-is-any
122 </pre>
123 causes PCRE to recognize any Unicode newline sequence.
124 </P>
125 <P>
126 Whatever line ending convention is selected when PCRE is built can be
127 overridden when the library functions are called. At build time it is
128 conventional to use the standard for your operating system.
129 </P>
130 <br><a name="SEC6" href="#TOC1">WHAT \R MATCHES</a><br>
131 <P>
132 By default, the sequence \R in a pattern matches any Unicode newline sequence,
133 whatever has been selected as the line ending sequence. If you specify
134 <pre>
135 --enable-bsr-anycrlf
136 </pre>
137 the default is changed so that \R matches only CR, LF, or CRLF. Whatever is
138 selected when PCRE is built can be overridden when the library functions are
139 called.
140 </P>
141 <br><a name="SEC7" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
142 <P>
143 The PCRE building process uses <b>libtool</b> to build both shared and static
144 Unix libraries by default. You can suppress one of these by adding one of
145 <pre>
146 --disable-shared
147 --disable-static
148 </pre>
149 to the <b>configure</b> command, as required.
150 </P>
151 <br><a name="SEC8" href="#TOC1">POSIX MALLOC USAGE</a><br>
152 <P>
153 When PCRE is called through the POSIX interface (see the
154 <a href="pcreposix.html"><b>pcreposix</b></a>
155 documentation), additional working storage is required for holding the pointers
156 to capturing substrings, because PCRE requires three integers per substring,
157 whereas the POSIX interface provides only two. If the number of expected
158 substrings is small, the wrapper function uses space on the stack, because this
159 is faster than using <b>malloc()</b> for each call. The default threshold above
160 which the stack is no longer used is 10; it can be changed by adding a setting
161 such as
162 <pre>
163 --with-posix-malloc-threshold=20
164 </pre>
165 to the <b>configure</b> command.
166 </P>
167 <br><a name="SEC9" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
168 <P>
169 Within a compiled pattern, offset values are used to point from one part to
170 another (for example, from an opening parenthesis to an alternation
171 metacharacter). By default, two-byte values are used for these offsets, leading
172 to a maximum size for a compiled pattern of around 64K. This is sufficient to
173 handle all but the most gigantic patterns. Nevertheless, some people do want to
174 process enormous patterns, so it is possible to compile PCRE to use three-byte
175 or four-byte offsets by adding a setting such as
176 <pre>
177 --with-link-size=3
178 </pre>
179 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
180 longer offsets slows down the operation of PCRE because it has to load
181 additional bytes when handling them.
182 </P>
183 <br><a name="SEC10" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
184 <P>
185 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
186 by making recursive calls to an internal function called <b>match()</b>. In
187 environments where the size of the stack is limited, this can severely limit
188 PCRE's operation. (The Unix environment does not usually suffer from this
189 problem, but it may sometimes be necessary to increase the maximum stack size.
190 There is a discussion in the
191 <a href="pcrestack.html"><b>pcrestack</b></a>
192 documentation.) An alternative approach to recursion that uses memory from the
193 heap to remember data, instead of using recursive function calls, has been
194 implemented to work round the problem of limited stack size. If you want to
195 build a version of PCRE that works this way, add
196 <pre>
197 --disable-stack-for-recursion
198 </pre>
199 to the <b>configure</b> command. With this configuration, PCRE will use the
200 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
201 management functions. By default these point to <b>malloc()</b> and
202 <b>free()</b>, but you can replace the pointers so that your own functions are
203 used.
204 </P>
205 <P>
206 Separate functions are provided rather than using <b>pcre_malloc</b> and
207 <b>pcre_free</b> because the usage is very predictable: the block sizes
208 requested are always the same, and the blocks are always freed in reverse
209 order. A calling program might be able to implement optimized functions that
210 perform better than <b>malloc()</b> and <b>free()</b>. PCRE runs noticeably more
211 slowly when built in this way. This option affects only the <b>pcre_exec()</b>
212 function; it is not relevant for the the <b>pcre_dfa_exec()</b> function.
213 </P>
214 <br><a name="SEC11" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
215 <P>
216 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
217 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
218 function. By controlling the maximum number of times this function may be
219 called during a single matching operation, a limit can be placed on the
220 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
221 at run time, as described in the
222 <a href="pcreapi.html"><b>pcreapi</b></a>
223 documentation. The default is 10 million, but this can be changed by adding a
224 setting such as
225 <pre>
226 --with-match-limit=500000
227 </pre>
228 to the <b>configure</b> command. This setting has no effect on the
229 <b>pcre_dfa_exec()</b> matching function.
230 </P>
231 <P>
232 In some environments it is desirable to limit the depth of recursive calls of
233 <b>match()</b> more strictly than the total number of calls, in order to
234 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
235 is specified) that is used. A second limit controls this; it defaults to the
236 value that is set for --with-match-limit, which imposes no additional
237 constraints. However, you can set a lower limit by adding, for example,
238 <pre>
239 --with-match-limit-recursion=10000
240 </pre>
241 to the <b>configure</b> command. This value can also be overridden at run time.
242 </P>
243 <br><a name="SEC12" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
244 <P>
245 PCRE uses fixed tables for processing characters whose code values are less
246 than 256. By default, PCRE is built with a set of tables that are distributed
247 in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes
248 only. If you add
249 <pre>
250 --enable-rebuild-chartables
251 </pre>
252 to the <b>configure</b> command, the distributed tables are no longer used.
253 Instead, a program called <b>dftables</b> is compiled and run. This outputs the
254 source for new set of tables, created in the default locale of your C runtime
255 system. (This method of replacing the tables does not work if you are cross
256 compiling, because <b>dftables</b> is run on the local host. If you need to
257 create alternative tables when cross compiling, you will have to do so "by
258 hand".)
259 </P>
260 <br><a name="SEC13" href="#TOC1">USING EBCDIC CODE</a><br>
261 <P>
262 PCRE assumes by default that it will run in an environment where the character
263 code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
264 most computer operating systems. PCRE can, however, be compiled to run in an
265 EBCDIC environment by adding
266 <pre>
267 --enable-ebcdic
268 </pre>
269 to the <b>configure</b> command. This setting implies
270 --enable-rebuild-chartables. You should only use it if you know that you are in
271 an EBCDIC environment (for example, an IBM mainframe operating system).
272 </P>
273 <br><a name="SEC14" href="#TOC1">SEE ALSO</a><br>
274 <P>
275 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
276 </P>
277 <br><a name="SEC15" href="#TOC1">AUTHOR</a><br>
278 <P>
279 Philip Hazel
280 <br>
281 University Computing Service
282 <br>
283 Cambridge CB2 3QH, England.
284 <br>
285 </P>
286 <br><a name="SEC16" href="#TOC1">REVISION</a><br>
287 <P>
288 Last updated: 21 September 2007
289 <br>
290 Copyright &copy; 1997-2007 University of Cambridge.
291 <br>
292 <p>
293 Return to the <a href="index.html">PCRE index page</a>.
294 </p>


Name Value
svn:eol-style native
svn:keywords "Author Date Id Revision Url"

  ViewVC Help
Powered by ViewVC 1.1.5