ViewVC logotype

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

Parent Directory Parent Directory | Revision Log Revision Log

Revision 453 - (show annotations)
Fri Sep 18 19:12:35 2009 UTC (11 years, 10 months ago) by ph10
File MIME type: text/html
File size: 15290 byte(s)
Add more explanation about recursive subpatterns, and make it possible to 
process the documenation without building a whole release.
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>
31 <li><a name="TOC16" href="#SEC16">SEE ALSO</a>
32 <li><a name="TOC17" href="#SEC17">AUTHOR</a>
33 <li><a name="TOC18" href="#SEC18">REVISION</a>
34 </ul>
35 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
36 <P>
37 This document describes the optional features of PCRE that can be selected when
38 the library is compiled. It assumes use of the <b>configure</b> script, where
39 the optional features are selected or deselected by providing options to
40 <b>configure</b> before running the <b>make</b> command. However, the same
41 options can be selected in both Unix-like and non-Unix-like environments using
42 the GUI facility of <b>cmake-gui</b> if you are using <b>CMake</b> instead of
43 <b>configure</b> to build PCRE.
44 </P>
45 <P>
46 There is a lot more information about building PCRE in non-Unix-like
47 environments in the file called <i>NON_UNIX_USE</i>, which is part of the PCRE
48 distribution. You should consult this file as well as the <i>README</i> file if
49 you are building in a non-Unix-like environment.
50 </P>
51 <P>
52 The complete list of options for <b>configure</b> (which includes the standard
53 ones such as the selection of the installation directory) can be obtained by
54 running
55 <pre>
56 ./configure --help
57 </pre>
58 The following sections include descriptions of options whose names begin with
59 --enable or --disable. These settings specify changes to the defaults for the
60 <b>configure</b> command. Because of the way that <b>configure</b> works,
61 --enable and --disable always come in pairs, so the complementary option always
62 exists as well, but as it specifies the default, it is not described.
63 </P>
64 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
65 <P>
66 By default, the <b>configure</b> script will search for a C++ compiler and C++
67 header files. If it finds them, it automatically builds the C++ wrapper library
68 for PCRE. You can disable this by adding
69 <pre>
70 --disable-cpp
71 </pre>
72 to the <b>configure</b> command.
73 </P>
74 <br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
75 <P>
76 To build PCRE with support for UTF-8 Unicode character strings, add
77 <pre>
78 --enable-utf8
79 </pre>
80 to the <b>configure</b> command. Of itself, this does not make PCRE treat
81 strings as UTF-8. As well as compiling PCRE with this option, you also have
82 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
83 function.
84 </P>
85 <P>
86 If you set --enable-utf8 when compiling in an EBCDIC environment, PCRE expects
87 its input to be either ASCII or UTF-8 (depending on the runtime option). It is
88 not possible to support both EBCDIC and UTF-8 codes in the same version of the
89 library. Consequently, --enable-utf8 and --enable-ebcdic are mutually
90 exclusive.
91 </P>
92 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
93 <P>
94 UTF-8 support allows PCRE to process character values greater than 255 in the
95 strings that it handles. On its own, however, it does not provide any
96 facilities for accessing the properties of such characters. If you want to be
97 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
98 character properties, you must add
99 <pre>
100 --enable-unicode-properties
101 </pre>
102 to the <b>configure</b> command. This implies UTF-8 support, even if you have
103 not explicitly requested it.
104 </P>
105 <P>
106 Including Unicode property support adds around 30K of tables to the PCRE
107 library. Only the general category properties such as <i>Lu</i> and <i>Nd</i> are
108 supported. Details are given in the
109 <a href="pcrepattern.html"><b>pcrepattern</b></a>
110 documentation.
111 </P>
112 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
113 <P>
114 By default, PCRE interprets the linefeed (LF) character as indicating the end
115 of a line. This is the normal newline character on Unix-like systems. You can
116 compile PCRE to use carriage return (CR) instead, by adding
117 <pre>
118 --enable-newline-is-cr
119 </pre>
120 to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
121 which explicitly specifies linefeed as the newline character.
122 <br>
123 <br>
124 Alternatively, you can specify that line endings are to be indicated by the two
125 character sequence CRLF. If you want this, add
126 <pre>
127 --enable-newline-is-crlf
128 </pre>
129 to the <b>configure</b> command. There is a fourth option, specified by
130 <pre>
131 --enable-newline-is-anycrlf
132 </pre>
133 which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
134 indicating a line ending. Finally, a fifth option, specified by
135 <pre>
136 --enable-newline-is-any
137 </pre>
138 causes PCRE to recognize any Unicode newline sequence.
139 </P>
140 <P>
141 Whatever line ending convention is selected when PCRE is built can be
142 overridden when the library functions are called. At build time it is
143 conventional to use the standard for your operating system.
144 </P>
145 <br><a name="SEC6" href="#TOC1">WHAT \R MATCHES</a><br>
146 <P>
147 By default, the sequence \R in a pattern matches any Unicode newline sequence,
148 whatever has been selected as the line ending sequence. If you specify
149 <pre>
150 --enable-bsr-anycrlf
151 </pre>
152 the default is changed so that \R matches only CR, LF, or CRLF. Whatever is
153 selected when PCRE is built can be overridden when the library functions are
154 called.
155 </P>
156 <br><a name="SEC7" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
157 <P>
158 The PCRE building process uses <b>libtool</b> to build both shared and static
159 Unix libraries by default. You can suppress one of these by adding one of
160 <pre>
161 --disable-shared
162 --disable-static
163 </pre>
164 to the <b>configure</b> command, as required.
165 </P>
166 <br><a name="SEC8" href="#TOC1">POSIX MALLOC USAGE</a><br>
167 <P>
168 When PCRE is called through the POSIX interface (see the
169 <a href="pcreposix.html"><b>pcreposix</b></a>
170 documentation), additional working storage is required for holding the pointers
171 to capturing substrings, because PCRE requires three integers per substring,
172 whereas the POSIX interface provides only two. If the number of expected
173 substrings is small, the wrapper function uses space on the stack, because this
174 is faster than using <b>malloc()</b> for each call. The default threshold above
175 which the stack is no longer used is 10; it can be changed by adding a setting
176 such as
177 <pre>
178 --with-posix-malloc-threshold=20
179 </pre>
180 to the <b>configure</b> command.
181 </P>
182 <br><a name="SEC9" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
183 <P>
184 Within a compiled pattern, offset values are used to point from one part to
185 another (for example, from an opening parenthesis to an alternation
186 metacharacter). By default, two-byte values are used for these offsets, leading
187 to a maximum size for a compiled pattern of around 64K. This is sufficient to
188 handle all but the most gigantic patterns. Nevertheless, some people do want to
189 process enormous patterns, so it is possible to compile PCRE to use three-byte
190 or four-byte offsets by adding a setting such as
191 <pre>
192 --with-link-size=3
193 </pre>
194 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
195 longer offsets slows down the operation of PCRE because it has to load
196 additional bytes when handling them.
197 </P>
198 <br><a name="SEC10" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
199 <P>
200 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
201 by making recursive calls to an internal function called <b>match()</b>. In
202 environments where the size of the stack is limited, this can severely limit
203 PCRE's operation. (The Unix environment does not usually suffer from this
204 problem, but it may sometimes be necessary to increase the maximum stack size.
205 There is a discussion in the
206 <a href="pcrestack.html"><b>pcrestack</b></a>
207 documentation.) An alternative approach to recursion that uses memory from the
208 heap to remember data, instead of using recursive function calls, has been
209 implemented to work round the problem of limited stack size. If you want to
210 build a version of PCRE that works this way, add
211 <pre>
212 --disable-stack-for-recursion
213 </pre>
214 to the <b>configure</b> command. With this configuration, PCRE will use the
215 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
216 management functions. By default these point to <b>malloc()</b> and
217 <b>free()</b>, but you can replace the pointers so that your own functions are
218 used.
219 </P>
220 <P>
221 Separate functions are provided rather than using <b>pcre_malloc</b> and
222 <b>pcre_free</b> because the usage is very predictable: the block sizes
223 requested are always the same, and the blocks are always freed in reverse
224 order. A calling program might be able to implement optimized functions that
225 perform better than <b>malloc()</b> and <b>free()</b>. PCRE runs noticeably more
226 slowly when built in this way. This option affects only the <b>pcre_exec()</b>
227 function; it is not relevant for the the <b>pcre_dfa_exec()</b> function.
228 </P>
229 <br><a name="SEC11" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
230 <P>
231 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
232 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
233 function. By controlling the maximum number of times this function may be
234 called during a single matching operation, a limit can be placed on the
235 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
236 at run time, as described in the
237 <a href="pcreapi.html"><b>pcreapi</b></a>
238 documentation. The default is 10 million, but this can be changed by adding a
239 setting such as
240 <pre>
241 --with-match-limit=500000
242 </pre>
243 to the <b>configure</b> command. This setting has no effect on the
244 <b>pcre_dfa_exec()</b> matching function.
245 </P>
246 <P>
247 In some environments it is desirable to limit the depth of recursive calls of
248 <b>match()</b> more strictly than the total number of calls, in order to
249 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
250 is specified) that is used. A second limit controls this; it defaults to the
251 value that is set for --with-match-limit, which imposes no additional
252 constraints. However, you can set a lower limit by adding, for example,
253 <pre>
254 --with-match-limit-recursion=10000
255 </pre>
256 to the <b>configure</b> command. This value can also be overridden at run time.
257 </P>
258 <br><a name="SEC12" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
259 <P>
260 PCRE uses fixed tables for processing characters whose code values are less
261 than 256. By default, PCRE is built with a set of tables that are distributed
262 in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes
263 only. If you add
264 <pre>
265 --enable-rebuild-chartables
266 </pre>
267 to the <b>configure</b> command, the distributed tables are no longer used.
268 Instead, a program called <b>dftables</b> is compiled and run. This outputs the
269 source for new set of tables, created in the default locale of your C runtime
270 system. (This method of replacing the tables does not work if you are cross
271 compiling, because <b>dftables</b> is run on the local host. If you need to
272 create alternative tables when cross compiling, you will have to do so "by
273 hand".)
274 </P>
275 <br><a name="SEC13" href="#TOC1">USING EBCDIC CODE</a><br>
276 <P>
277 PCRE assumes by default that it will run in an environment where the character
278 code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
279 most computer operating systems. PCRE can, however, be compiled to run in an
280 EBCDIC environment by adding
281 <pre>
282 --enable-ebcdic
283 </pre>
284 to the <b>configure</b> command. This setting implies
285 --enable-rebuild-chartables. You should only use it if you know that you are in
286 an EBCDIC environment (for example, an IBM mainframe operating system). The
287 --enable-ebcdic option is incompatible with --enable-utf8.
288 </P>
290 <P>
291 By default, <b>pcregrep</b> reads all files as plain text. You can build it so
292 that it recognizes files whose names end in <b>.gz</b> or <b>.bz2</b>, and reads
293 them with <b>libz</b> or <b>libbz2</b>, respectively, by adding one or both of
294 <pre>
295 --enable-pcregrep-libz
296 --enable-pcregrep-libbz2
297 </pre>
298 to the <b>configure</b> command. These options naturally require that the
299 relevant libraries are installed on your system. Configuration will fail if
300 they are not.
301 </P>
302 <br><a name="SEC15" href="#TOC1">PCRETEST OPTION FOR LIBREADLINE SUPPORT</a><br>
303 <P>
304 If you add
305 <pre>
306 --enable-pcretest-libreadline
307 </pre>
308 to the <b>configure</b> command, <b>pcretest</b> is linked with the
309 <b>libreadline</b> library, and when its input is from a terminal, it reads it
310 using the <b>readline()</b> function. This provides line-editing and history
311 facilities. Note that <b>libreadline</b> is GPL-licenced, so if you distribute a
312 binary of <b>pcretest</b> linked in this way, there may be licensing issues.
313 </P>
314 <P>
315 Setting this option causes the <b>-lreadline</b> option to be added to the
316 <b>pcretest</b> build. In many operating environments with a sytem-installed
317 <b>libreadline</b> this is sufficient. However, in some environments (e.g.
318 if an unmodified distribution version of readline is in use), some extra
319 configuration may be necessary. The INSTALL file for <b>libreadline</b> says
320 this:
321 <pre>
322 "Readline uses the termcap functions, but does not link with the
323 termcap or curses library itself, allowing applications which link
324 with readline the to choose an appropriate library."
325 </pre>
326 If your environment has not been set up so that an appropriate library is
327 automatically included, you may need to add something like
328 <pre>
329 LIBS="-ncurses"
330 </pre>
331 immediately before the <b>configure</b> command.
332 </P>
333 <br><a name="SEC16" href="#TOC1">SEE ALSO</a><br>
334 <P>
335 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
336 </P>
337 <br><a name="SEC17" href="#TOC1">AUTHOR</a><br>
338 <P>
339 Philip Hazel
340 <br>
341 University Computing Service
342 <br>
343 Cambridge CB2 3QH, England.
344 <br>
345 </P>
346 <br><a name="SEC18" href="#TOC1">REVISION</a><br>
347 <P>
348 Last updated: 06 September 2009
349 <br>
350 Copyright &copy; 1997-2009 University of Cambridge.
351 <br>
352 <p>
353 Return to the <a href="index.html">PCRE index page</a>.
354 </p>


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

  ViewVC Help
Powered by ViewVC 1.1.5