/[pcre]/code/trunk/doc/html/pcrebuild.html
ViewVC logotype

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

Parent Directory Parent Directory | Revision Log Revision Log


Revision 93 - (show annotations) (download) (as text)
Sat Feb 24 21:41:42 2007 UTC (7 years, 9 months ago) by nigel
File MIME type: text/html
File size: 10278 byte(s)
Load pcre-7.0 into code/trunk.

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">USING EBCDIC CODE</a>
27 <li><a name="TOC12" href="#SEC12">SEE ALSO</a>
28 </ul>
29 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
30 <P>
31 This document describes the optional features of PCRE that can be selected when
32 the library is compiled. They are all selected, or deselected, by providing
33 options to the <b>configure</b> script that is run before the <b>make</b>
34 command. The complete list of options for <b>configure</b> (which includes the
35 standard ones such as the selection of the installation directory) can be
36 obtained by running
37 <pre>
38 ./configure --help
39 </pre>
40 The following sections describe certain options whose names begin with --enable
41 or --disable. These settings specify changes to the defaults for the
42 <b>configure</b> command. Because of the way that <b>configure</b> works,
43 --enable and --disable always come in pairs, so the complementary option always
44 exists as well, but as it specifies the default, it is not described.
45 </P>
46 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
47 <P>
48 By default, the <b>configure</b> script will search for a C++ compiler and C++
49 header files. If it finds them, it automatically builds the C++ wrapper library
50 for PCRE. You can disable this by adding
51 <pre>
52 --disable-cpp
53 </pre>
54 to the <b>configure</b> command.
55 </P>
56 <br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
57 <P>
58 To build PCRE with support for UTF-8 character strings, add
59 <pre>
60 --enable-utf8
61 </pre>
62 to the <b>configure</b> command. Of itself, this does not make PCRE treat
63 strings as UTF-8. As well as compiling PCRE with this option, you also have
64 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
65 function.
66 </P>
67 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
68 <P>
69 UTF-8 support allows PCRE to process character values greater than 255 in the
70 strings that it handles. On its own, however, it does not provide any
71 facilities for accessing the properties of such characters. If you want to be
72 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
73 character properties, you must add
74 <pre>
75 --enable-unicode-properties
76 </pre>
77 to the <b>configure</b> command. This implies UTF-8 support, even if you have
78 not explicitly requested it.
79 </P>
80 <P>
81 Including Unicode property support adds around 90K of tables to the PCRE
82 library, approximately doubling its size. Only the general category properties
83 such as <i>Lu</i> and <i>Nd</i> are supported. Details are given in the
84 <a href="pcrepattern.html"><b>pcrepattern</b></a>
85 documentation.
86 </P>
87 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
88 <P>
89 By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
90 of a line. This is the normal newline character on Unix-like systems. You can
91 compile PCRE to use character 13 (carriage return, CR) instead, by adding
92 <pre>
93 --enable-newline-is-cr
94 </pre>
95 to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
96 which explicitly specifies linefeed as the newline character.
97 <br>
98 <br>
99 Alternatively, you can specify that line endings are to be indicated by the two
100 character sequence CRLF. If you want this, add
101 <pre>
102 --enable-newline-is-crlf
103 </pre>
104 to the <b>configure</b> command. There is a fourth option, specified by
105 <pre>
106 --enable-newline-is-any
107 </pre>
108 which causes PCRE to recognize any Unicode newline sequence.
109 </P>
110 <P>
111 Whatever line ending convention is selected when PCRE is built can be
112 overridden when the library functions are called. At build time it is
113 conventional to use the standard for your operating system.
114 </P>
115 <br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
116 <P>
117 The PCRE building process uses <b>libtool</b> to build both shared and static
118 Unix libraries by default. You can suppress one of these by adding one of
119 <pre>
120 --disable-shared
121 --disable-static
122 </pre>
123 to the <b>configure</b> command, as required.
124 </P>
125 <br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
126 <P>
127 When PCRE is called through the POSIX interface (see the
128 <a href="pcreposix.html"><b>pcreposix</b></a>
129 documentation), additional working storage is required for holding the pointers
130 to capturing substrings, because PCRE requires three integers per substring,
131 whereas the POSIX interface provides only two. If the number of expected
132 substrings is small, the wrapper function uses space on the stack, because this
133 is faster than using <b>malloc()</b> for each call. The default threshold above
134 which the stack is no longer used is 10; it can be changed by adding a setting
135 such as
136 <pre>
137 --with-posix-malloc-threshold=20
138 </pre>
139 to the <b>configure</b> command.
140 </P>
141 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
142 <P>
143 Within a compiled pattern, offset values are used to point from one part to
144 another (for example, from an opening parenthesis to an alternation
145 metacharacter). By default, two-byte values are used for these offsets, leading
146 to a maximum size for a compiled pattern of around 64K. This is sufficient to
147 handle all but the most gigantic patterns. Nevertheless, some people do want to
148 process enormous patterns, so it is possible to compile PCRE to use three-byte
149 or four-byte offsets by adding a setting such as
150 <pre>
151 --with-link-size=3
152 </pre>
153 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
154 longer offsets slows down the operation of PCRE because it has to load
155 additional bytes when handling them.
156 </P>
157 <P>
158 If you build PCRE with an increased link size, test 2 (and test 5 if you are
159 using UTF-8) will fail. Part of the output of these tests is a representation
160 of the compiled pattern, and this changes with the link size.
161 </P>
162 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
163 <P>
164 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
165 by making recursive calls to an internal function called <b>match()</b>. In
166 environments where the size of the stack is limited, this can severely limit
167 PCRE's operation. (The Unix environment does not usually suffer from this
168 problem, but it may sometimes be necessary to increase the maximum stack size.
169 There is a discussion in the
170 <a href="pcrestack.html"><b>pcrestack</b></a>
171 documentation.) An alternative approach to recursion that uses memory from the
172 heap to remember data, instead of using recursive function calls, has been
173 implemented to work round the problem of limited stack size. If you want to
174 build a version of PCRE that works this way, add
175 <pre>
176 --disable-stack-for-recursion
177 </pre>
178 to the <b>configure</b> command. With this configuration, PCRE will use the
179 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
180 management functions. Separate functions are provided because the usage is very
181 predictable: the block sizes requested are always the same, and the blocks are
182 always freed in reverse order. A calling program might be able to implement
183 optimized functions that perform better than the standard <b>malloc()</b> and
184 <b>free()</b> functions. PCRE runs noticeably more slowly when built in this
185 way. This option affects only the <b>pcre_exec()</b> function; it is not
186 relevant for the the <b>pcre_dfa_exec()</b> function.
187 </P>
188 <br><a name="SEC10" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
189 <P>
190 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
191 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
192 function. By controlling the maximum number of times this function may be
193 called during a single matching operation, a limit can be placed on the
194 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
195 at run time, as described in the
196 <a href="pcreapi.html"><b>pcreapi</b></a>
197 documentation. The default is 10 million, but this can be changed by adding a
198 setting such as
199 <pre>
200 --with-match-limit=500000
201 </pre>
202 to the <b>configure</b> command. This setting has no effect on the
203 <b>pcre_dfa_exec()</b> matching function.
204 </P>
205 <P>
206 In some environments it is desirable to limit the depth of recursive calls of
207 <b>match()</b> more strictly than the total number of calls, in order to
208 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
209 is specified) that is used. A second limit controls this; it defaults to the
210 value that is set for --with-match-limit, which imposes no additional
211 constraints. However, you can set a lower limit by adding, for example,
212 <pre>
213 --with-match-limit-recursion=10000
214 </pre>
215 to the <b>configure</b> command. This value can also be overridden at run time.
216 </P>
217 <br><a name="SEC11" href="#TOC1">USING EBCDIC CODE</a><br>
218 <P>
219 PCRE assumes by default that it will run in an environment where the character
220 code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
221 compiled to run in an EBCDIC environment by adding
222 <pre>
223 --enable-ebcdic
224 </pre>
225 to the <b>configure</b> command.
226 </P>
227 <br><a name="SEC12" href="#TOC1">SEE ALSO</a><br>
228 <P>
229 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
230 </P>
231 <P>
232 Last updated: 30 November 2006
233 <br>
234 Copyright &copy; 1997-2006 University of Cambridge.
235 <p>
236 Return to the <a href="index.html">PCRE index page</a>.
237 </p>

webmaster@exim.org
ViewVC Help
Powered by ViewVC 1.1.12