ViewVC logotype

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

Parent Directory Parent Directory | Revision Log Revision Log

Revision 197 - (show annotations)
Tue Jul 31 10:50:18 2007 UTC (14 years, 2 months ago) by ph10
File MIME type: text/html
File size: 11818 byte(s)
Error occurred while calculating annotation data.
Abolish the NULLWSLIMIT error at the expense of using more stack when an 
unlimited repeat could match an empty string. Also, doc tidies for a test 
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>
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-anycrlf
110 </pre>
111 which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
112 indicating a line ending. Finally, a fifth option, specified by
113 <pre>
114 --enable-newline-is-any
115 </pre>
116 causes PCRE to recognize any Unicode newline sequence.
117 </P>
118 <P>
119 Whatever line ending convention is selected when PCRE is built can be
120 overridden when the library functions are called. At build time it is
121 conventional to use the standard for your operating system.
122 </P>
123 <br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
124 <P>
125 The PCRE building process uses <b>libtool</b> to build both shared and static
126 Unix libraries by default. You can suppress one of these by adding one of
127 <pre>
128 --disable-shared
129 --disable-static
130 </pre>
131 to the <b>configure</b> command, as required.
132 </P>
133 <br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
134 <P>
135 When PCRE is called through the POSIX interface (see the
136 <a href="pcreposix.html"><b>pcreposix</b></a>
137 documentation), additional working storage is required for holding the pointers
138 to capturing substrings, because PCRE requires three integers per substring,
139 whereas the POSIX interface provides only two. If the number of expected
140 substrings is small, the wrapper function uses space on the stack, because this
141 is faster than using <b>malloc()</b> for each call. The default threshold above
142 which the stack is no longer used is 10; it can be changed by adding a setting
143 such as
144 <pre>
145 --with-posix-malloc-threshold=20
146 </pre>
147 to the <b>configure</b> command.
148 </P>
149 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
150 <P>
151 Within a compiled pattern, offset values are used to point from one part to
152 another (for example, from an opening parenthesis to an alternation
153 metacharacter). By default, two-byte values are used for these offsets, leading
154 to a maximum size for a compiled pattern of around 64K. This is sufficient to
155 handle all but the most gigantic patterns. Nevertheless, some people do want to
156 process enormous patterns, so it is possible to compile PCRE to use three-byte
157 or four-byte offsets by adding a setting such as
158 <pre>
159 --with-link-size=3
160 </pre>
161 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
162 longer offsets slows down the operation of PCRE because it has to load
163 additional bytes when handling them.
164 </P>
165 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
166 <P>
167 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
168 by making recursive calls to an internal function called <b>match()</b>. In
169 environments where the size of the stack is limited, this can severely limit
170 PCRE's operation. (The Unix environment does not usually suffer from this
171 problem, but it may sometimes be necessary to increase the maximum stack size.
172 There is a discussion in the
173 <a href="pcrestack.html"><b>pcrestack</b></a>
174 documentation.) An alternative approach to recursion that uses memory from the
175 heap to remember data, instead of using recursive function calls, has been
176 implemented to work round the problem of limited stack size. If you want to
177 build a version of PCRE that works this way, add
178 <pre>
179 --disable-stack-for-recursion
180 </pre>
181 to the <b>configure</b> command. With this configuration, PCRE will use the
182 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
183 management functions. By default these point to <b>malloc()</b> and
184 <b>free()</b>, but you can replace the pointers so that your own functions are
185 used.
186 </P>
187 <P>
188 Separate functions are provided rather than using <b>pcre_malloc</b> and
189 <b>pcre_free</b> because the usage is very predictable: the block sizes
190 requested are always the same, and the blocks are always freed in reverse
191 order. A calling program might be able to implement optimized functions that
192 perform better than <b>malloc()</b> and <b>free()</b>. PCRE runs noticeably more
193 slowly when built in this way. This option affects only the <b>pcre_exec()</b>
194 function; it is not relevant for the the <b>pcre_dfa_exec()</b> function.
195 </P>
196 <br><a name="SEC10" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
197 <P>
198 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
199 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
200 function. By controlling the maximum number of times this function may be
201 called during a single matching operation, a limit can be placed on the
202 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
203 at run time, as described in the
204 <a href="pcreapi.html"><b>pcreapi</b></a>
205 documentation. The default is 10 million, but this can be changed by adding a
206 setting such as
207 <pre>
208 --with-match-limit=500000
209 </pre>
210 to the <b>configure</b> command. This setting has no effect on the
211 <b>pcre_dfa_exec()</b> matching function.
212 </P>
213 <P>
214 In some environments it is desirable to limit the depth of recursive calls of
215 <b>match()</b> more strictly than the total number of calls, in order to
216 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
217 is specified) that is used. A second limit controls this; it defaults to the
218 value that is set for --with-match-limit, which imposes no additional
219 constraints. However, you can set a lower limit by adding, for example,
220 <pre>
221 --with-match-limit-recursion=10000
222 </pre>
223 to the <b>configure</b> command. This value can also be overridden at run time.
224 </P>
225 <br><a name="SEC11" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
226 <P>
227 PCRE uses fixed tables for processing characters whose code values are less
228 than 256. By default, PCRE is built with a set of tables that are distributed
229 in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes
230 only. If you add
231 <pre>
232 --enable-rebuild-chartables
233 </pre>
234 to the <b>configure</b> command, the distributed tables are no longer used.
235 Instead, a program called <b>dftables</b> is compiled and run. This outputs the
236 source for new set of tables, created in the default locale of your C runtime
237 system. (This method of replacing the tables does not work if you are cross
238 compiling, because <b>dftables</b> is run on the local host. If you need to
239 create alternative tables when cross compiling, you will have to do so "by
240 hand".)
241 </P>
242 <br><a name="SEC12" href="#TOC1">USING EBCDIC CODE</a><br>
243 <P>
244 PCRE assumes by default that it will run in an environment where the character
245 code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
246 most computer operating systems. PCRE can, however, be compiled to run in an
247 EBCDIC environment by adding
248 <pre>
249 --enable-ebcdic
250 </pre>
251 to the <b>configure</b> command. This setting implies
252 --enable-rebuild-chartables. You should only use it if you know that you are in
253 an EBCDIC environment (for example, an IBM mainframe operating system).
254 </P>
255 <br><a name="SEC13" href="#TOC1">SEE ALSO</a><br>
256 <P>
257 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
258 </P>
259 <br><a name="SEC14" href="#TOC1">AUTHOR</a><br>
260 <P>
261 Philip Hazel
262 <br>
263 University Computing Service
264 <br>
265 Cambridge CB2 3QH, England.
266 <br>
267 </P>
268 <br><a name="SEC15" href="#TOC1">REVISION</a><br>
269 <P>
270 Last updated: 30 July 2007
271 <br>
272 Copyright &copy; 1997-2007 University of Cambridge.
273 <br>
274 <p>
275 Return to the <a href="index.html">PCRE index page</a>.
276 </p>


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

  ViewVC Help
Powered by ViewVC 1.1.5