ViewVC logotype

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

Parent Directory Parent Directory | Revision Log Revision Log

Revision 231 - (show annotations)
Tue Sep 11 11:15:33 2007 UTC (13 years, 1 month ago) by ph10
File MIME type: text/html
File size: 12290 byte(s)
Add facility to make \R match only CR, LF, or CRLF.
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. They are all selected, or deselected, by providing
37 options to the <b>configure</b> script that is run before the <b>make</b>
38 command. The complete list of options for <b>configure</b> (which includes the
39 standard ones such as the selection of the installation directory) can be
40 obtained by running
41 <pre>
42 ./configure --help
43 </pre>
44 The following sections include descriptions of options whose names begin with
45 --enable or --disable. These settings specify changes to the defaults for the
46 <b>configure</b> command. Because of the way that <b>configure</b> works,
47 --enable and --disable always come in pairs, so the complementary option always
48 exists as well, but as it specifies the default, it is not described.
49 </P>
50 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
51 <P>
52 By default, the <b>configure</b> script will search for a C++ compiler and C++
53 header files. If it finds them, it automatically builds the C++ wrapper library
54 for PCRE. You can disable this by adding
55 <pre>
56 --disable-cpp
57 </pre>
58 to the <b>configure</b> command.
59 </P>
60 <br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
61 <P>
62 To build PCRE with support for UTF-8 character strings, add
63 <pre>
64 --enable-utf8
65 </pre>
66 to the <b>configure</b> command. Of itself, this does not make PCRE treat
67 strings as UTF-8. As well as compiling PCRE with this option, you also have
68 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
69 function.
70 </P>
71 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
72 <P>
73 UTF-8 support allows PCRE to process character values greater than 255 in the
74 strings that it handles. On its own, however, it does not provide any
75 facilities for accessing the properties of such characters. If you want to be
76 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
77 character properties, you must add
78 <pre>
79 --enable-unicode-properties
80 </pre>
81 to the <b>configure</b> command. This implies UTF-8 support, even if you have
82 not explicitly requested it.
83 </P>
84 <P>
85 Including Unicode property support adds around 30K of tables to the PCRE
86 library. Only the general category properties such as <i>Lu</i> and <i>Nd</i> are
87 supported. Details are given in the
88 <a href="pcrepattern.html"><b>pcrepattern</b></a>
89 documentation.
90 </P>
91 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
92 <P>
93 By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
94 of a line. This is the normal newline character on Unix-like systems. You can
95 compile PCRE to use character 13 (carriage return, CR) instead, by adding
96 <pre>
97 --enable-newline-is-cr
98 </pre>
99 to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
100 which explicitly specifies linefeed as the newline character.
101 <br>
102 <br>
103 Alternatively, you can specify that line endings are to be indicated by the two
104 character sequence CRLF. If you want this, add
105 <pre>
106 --enable-newline-is-crlf
107 </pre>
108 to the <b>configure</b> command. There is a fourth option, specified by
109 <pre>
110 --enable-newline-is-anycrlf
111 </pre>
112 which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
113 indicating a line ending. Finally, a fifth option, specified by
114 <pre>
115 --enable-newline-is-any
116 </pre>
117 causes PCRE to recognize any Unicode newline sequence.
118 </P>
119 <P>
120 Whatever line ending convention is selected when PCRE is built can be
121 overridden when the library functions are called. At build time it is
122 conventional to use the standard for your operating system.
123 </P>
124 <br><a name="SEC6" href="#TOC1">WHAT \R MATCHES</a><br>
125 <P>
126 By default, the sequence \R in a pattern matches any Unicode newline sequence,
127 whatever has been selected as the line ending sequence. If you specify
128 <pre>
129 --enable-bsr-anycrlf
130 </pre>
131 the default is changed so that \R matches only CR, LF, or CRLF. Whatever is
132 selected when PCRE is built can be overridden when the library functions are
133 called.
134 </P>
135 <br><a name="SEC7" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
136 <P>
137 The PCRE building process uses <b>libtool</b> to build both shared and static
138 Unix libraries by default. You can suppress one of these by adding one of
139 <pre>
140 --disable-shared
141 --disable-static
142 </pre>
143 to the <b>configure</b> command, as required.
144 </P>
145 <br><a name="SEC8" href="#TOC1">POSIX MALLOC USAGE</a><br>
146 <P>
147 When PCRE is called through the POSIX interface (see the
148 <a href="pcreposix.html"><b>pcreposix</b></a>
149 documentation), additional working storage is required for holding the pointers
150 to capturing substrings, because PCRE requires three integers per substring,
151 whereas the POSIX interface provides only two. If the number of expected
152 substrings is small, the wrapper function uses space on the stack, because this
153 is faster than using <b>malloc()</b> for each call. The default threshold above
154 which the stack is no longer used is 10; it can be changed by adding a setting
155 such as
156 <pre>
157 --with-posix-malloc-threshold=20
158 </pre>
159 to the <b>configure</b> command.
160 </P>
161 <br><a name="SEC9" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
162 <P>
163 Within a compiled pattern, offset values are used to point from one part to
164 another (for example, from an opening parenthesis to an alternation
165 metacharacter). By default, two-byte values are used for these offsets, leading
166 to a maximum size for a compiled pattern of around 64K. This is sufficient to
167 handle all but the most gigantic patterns. Nevertheless, some people do want to
168 process enormous patterns, so it is possible to compile PCRE to use three-byte
169 or four-byte offsets by adding a setting such as
170 <pre>
171 --with-link-size=3
172 </pre>
173 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
174 longer offsets slows down the operation of PCRE because it has to load
175 additional bytes when handling them.
176 </P>
177 <br><a name="SEC10" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
178 <P>
179 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
180 by making recursive calls to an internal function called <b>match()</b>. In
181 environments where the size of the stack is limited, this can severely limit
182 PCRE's operation. (The Unix environment does not usually suffer from this
183 problem, but it may sometimes be necessary to increase the maximum stack size.
184 There is a discussion in the
185 <a href="pcrestack.html"><b>pcrestack</b></a>
186 documentation.) An alternative approach to recursion that uses memory from the
187 heap to remember data, instead of using recursive function calls, has been
188 implemented to work round the problem of limited stack size. If you want to
189 build a version of PCRE that works this way, add
190 <pre>
191 --disable-stack-for-recursion
192 </pre>
193 to the <b>configure</b> command. With this configuration, PCRE will use the
194 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
195 management functions. By default these point to <b>malloc()</b> and
196 <b>free()</b>, but you can replace the pointers so that your own functions are
197 used.
198 </P>
199 <P>
200 Separate functions are provided rather than using <b>pcre_malloc</b> and
201 <b>pcre_free</b> because the usage is very predictable: the block sizes
202 requested are always the same, and the blocks are always freed in reverse
203 order. A calling program might be able to implement optimized functions that
204 perform better than <b>malloc()</b> and <b>free()</b>. PCRE runs noticeably more
205 slowly when built in this way. This option affects only the <b>pcre_exec()</b>
206 function; it is not relevant for the the <b>pcre_dfa_exec()</b> function.
207 </P>
208 <br><a name="SEC11" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
209 <P>
210 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
211 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
212 function. By controlling the maximum number of times this function may be
213 called during a single matching operation, a limit can be placed on the
214 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
215 at run time, as described in the
216 <a href="pcreapi.html"><b>pcreapi</b></a>
217 documentation. The default is 10 million, but this can be changed by adding a
218 setting such as
219 <pre>
220 --with-match-limit=500000
221 </pre>
222 to the <b>configure</b> command. This setting has no effect on the
223 <b>pcre_dfa_exec()</b> matching function.
224 </P>
225 <P>
226 In some environments it is desirable to limit the depth of recursive calls of
227 <b>match()</b> more strictly than the total number of calls, in order to
228 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
229 is specified) that is used. A second limit controls this; it defaults to the
230 value that is set for --with-match-limit, which imposes no additional
231 constraints. However, you can set a lower limit by adding, for example,
232 <pre>
233 --with-match-limit-recursion=10000
234 </pre>
235 to the <b>configure</b> command. This value can also be overridden at run time.
236 </P>
237 <br><a name="SEC12" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
238 <P>
239 PCRE uses fixed tables for processing characters whose code values are less
240 than 256. By default, PCRE is built with a set of tables that are distributed
241 in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes
242 only. If you add
243 <pre>
244 --enable-rebuild-chartables
245 </pre>
246 to the <b>configure</b> command, the distributed tables are no longer used.
247 Instead, a program called <b>dftables</b> is compiled and run. This outputs the
248 source for new set of tables, created in the default locale of your C runtime
249 system. (This method of replacing the tables does not work if you are cross
250 compiling, because <b>dftables</b> is run on the local host. If you need to
251 create alternative tables when cross compiling, you will have to do so "by
252 hand".)
253 </P>
254 <br><a name="SEC13" href="#TOC1">USING EBCDIC CODE</a><br>
255 <P>
256 PCRE assumes by default that it will run in an environment where the character
257 code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
258 most computer operating systems. PCRE can, however, be compiled to run in an
259 EBCDIC environment by adding
260 <pre>
261 --enable-ebcdic
262 </pre>
263 to the <b>configure</b> command. This setting implies
264 --enable-rebuild-chartables. You should only use it if you know that you are in
265 an EBCDIC environment (for example, an IBM mainframe operating system).
266 </P>
267 <br><a name="SEC14" href="#TOC1">SEE ALSO</a><br>
268 <P>
269 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
270 </P>
271 <br><a name="SEC15" href="#TOC1">AUTHOR</a><br>
272 <P>
273 Philip Hazel
274 <br>
275 University Computing Service
276 <br>
277 Cambridge CB2 3QH, England.
278 <br>
279 </P>
280 <br><a name="SEC16" href="#TOC1">REVISION</a><br>
281 <P>
282 Last updated: 11 September 2007
283 <br>
284 Copyright &copy; 1997-2007 University of Cambridge.
285 <br>
286 <p>
287 Return to the <a href="index.html">PCRE index page</a>.
288 </p>


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

  ViewVC Help
Powered by ViewVC 1.1.5