/[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 91 - (show annotations) (download) (as text)
Sat Feb 24 21:41:34 2007 UTC (7 years, 5 months ago) by nigel
File MIME type: text/html
File size: 9978 byte(s)
Load pcre-6.7 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 </ul>
28 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
29 <P>
30 This document describes the optional features of PCRE that can be selected when
31 the library is compiled. They are all selected, or deselected, by providing
32 options to the <b>configure</b> script that is run before the <b>make</b>
33 command. The complete list of options for <b>configure</b> (which includes the
34 standard ones such as the selection of the installation directory) can be
35 obtained by running
36 <pre>
37 ./configure --help
38 </pre>
39 The following sections describe certain options whose names begin with --enable
40 or --disable. These settings specify changes to the defaults for the
41 <b>configure</b> command. Because of the way that <b>configure</b> works,
42 --enable and --disable always come in pairs, so the complementary option always
43 exists as well, but as it specifies the default, it is not described.
44 </P>
45 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
46 <P>
47 By default, the <b>configure</b> script will search for a C++ compiler and C++
48 header files. If it finds them, it automatically builds the C++ wrapper library
49 for PCRE. You can disable this by adding
50 <pre>
51 --disable-cpp
52 </pre>
53 to the <b>configure</b> command.
54 </P>
55 <br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
56 <P>
57 To build PCRE with support for UTF-8 character strings, add
58 <pre>
59 --enable-utf8
60 </pre>
61 to the <b>configure</b> command. Of itself, this does not make PCRE treat
62 strings as UTF-8. As well as compiling PCRE with this option, you also have
63 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
64 function.
65 </P>
66 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
67 <P>
68 UTF-8 support allows PCRE to process character values greater than 255 in the
69 strings that it handles. On its own, however, it does not provide any
70 facilities for accessing the properties of such characters. If you want to be
71 able to use the pattern escapes \P, \p, and \X, which refer to Unicode
72 character properties, you must add
73 <pre>
74 --enable-unicode-properties
75 </pre>
76 to the <b>configure</b> command. This implies UTF-8 support, even if you have
77 not explicitly requested it.
78 </P>
79 <P>
80 Including Unicode property support adds around 90K of tables to the PCRE
81 library, approximately doubling its size. Only the general category properties
82 such as <i>Lu</i> and <i>Nd</i> are supported. Details are given in the
83 <a href="pcrepattern.html"><b>pcrepattern</b></a>
84 documentation.
85 </P>
86 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
87 <P>
88 By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
89 of a line. This is the normal newline character on Unix-like systems. You can
90 compile PCRE to use character 13 (carriage return, CR) instead, by adding
91 <pre>
92 --enable-newline-is-cr
93 </pre>
94 to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
95 which explicitly specifies linefeed as the newline character.
96 <br>
97 <br>
98 Alternatively, you can specify that line endings are to be indicated by the two
99 character sequence CRLF. If you want this, add
100 <pre>
101 --enable-newline-is-crlf
102 </pre>
103 to the <b>configure</b> command. Whatever line ending convention is selected
104 when PCRE is built can be overridden when the library functions are called. At
105 build time it is conventional to use the standard for your operating system.
106 </P>
107 <br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
108 <P>
109 The PCRE building process uses <b>libtool</b> to build both shared and static
110 Unix libraries by default. You can suppress one of these by adding one of
111 <pre>
112 --disable-shared
113 --disable-static
114 </pre>
115 to the <b>configure</b> command, as required.
116 </P>
117 <br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
118 <P>
119 When PCRE is called through the POSIX interface (see the
120 <a href="pcreposix.html"><b>pcreposix</b></a>
121 documentation), additional working storage is required for holding the pointers
122 to capturing substrings, because PCRE requires three integers per substring,
123 whereas the POSIX interface provides only two. If the number of expected
124 substrings is small, the wrapper function uses space on the stack, because this
125 is faster than using <b>malloc()</b> for each call. The default threshold above
126 which the stack is no longer used is 10; it can be changed by adding a setting
127 such as
128 <pre>
129 --with-posix-malloc-threshold=20
130 </pre>
131 to the <b>configure</b> command.
132 </P>
133 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
134 <P>
135 Within a compiled pattern, offset values are used to point from one part to
136 another (for example, from an opening parenthesis to an alternation
137 metacharacter). By default, two-byte values are used for these offsets, leading
138 to a maximum size for a compiled pattern of around 64K. This is sufficient to
139 handle all but the most gigantic patterns. Nevertheless, some people do want to
140 process enormous patterns, so it is possible to compile PCRE to use three-byte
141 or four-byte offsets by adding a setting such as
142 <pre>
143 --with-link-size=3
144 </pre>
145 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
146 longer offsets slows down the operation of PCRE because it has to load
147 additional bytes when handling them.
148 </P>
149 <P>
150 If you build PCRE with an increased link size, test 2 (and test 5 if you are
151 using UTF-8) will fail. Part of the output of these tests is a representation
152 of the compiled pattern, and this changes with the link size.
153 </P>
154 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
155 <P>
156 When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
157 by making recursive calls to an internal function called <b>match()</b>. In
158 environments where the size of the stack is limited, this can severely limit
159 PCRE's operation. (The Unix environment does not usually suffer from this
160 problem, but it may sometimes be necessary to increase the maximum stack size.
161 There is a discussion in the
162 <a href="pcrestack.html"><b>pcrestack</b></a>
163 documentation.) An alternative approach to recursion that uses memory from the
164 heap to remember data, instead of using recursive function calls, has been
165 implemented to work round the problem of limited stack size. If you want to
166 build a version of PCRE that works this way, add
167 <pre>
168 --disable-stack-for-recursion
169 </pre>
170 to the <b>configure</b> command. With this configuration, PCRE will use the
171 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
172 management functions. Separate functions are provided because the usage is very
173 predictable: the block sizes requested are always the same, and the blocks are
174 always freed in reverse order. A calling program might be able to implement
175 optimized functions that perform better than the standard <b>malloc()</b> and
176 <b>free()</b> functions. PCRE runs noticeably more slowly when built in this
177 way. This option affects only the <b>pcre_exec()</b> function; it is not
178 relevant for the the <b>pcre_dfa_exec()</b> function.
179 </P>
180 <br><a name="SEC10" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
181 <P>
182 Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
183 (sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
184 function. By controlling the maximum number of times this function may be
185 called during a single matching operation, a limit can be placed on the
186 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
187 at run time, as described in the
188 <a href="pcreapi.html"><b>pcreapi</b></a>
189 documentation. The default is 10 million, but this can be changed by adding a
190 setting such as
191 <pre>
192 --with-match-limit=500000
193 </pre>
194 to the <b>configure</b> command. This setting has no effect on the
195 <b>pcre_dfa_exec()</b> matching function.
196 </P>
197 <P>
198 In some environments it is desirable to limit the depth of recursive calls of
199 <b>match()</b> more strictly than the total number of calls, in order to
200 restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
201 is specified) that is used. A second limit controls this; it defaults to the
202 value that is set for --with-match-limit, which imposes no additional
203 constraints. However, you can set a lower limit by adding, for example,
204 <pre>
205 --with-match-limit-recursion=10000
206 </pre>
207 to the <b>configure</b> command. This value can also be overridden at run time.
208 </P>
209 <br><a name="SEC11" href="#TOC1">USING EBCDIC CODE</a><br>
210 <P>
211 PCRE assumes by default that it will run in an environment where the character
212 code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
213 compiled to run in an EBCDIC environment by adding
214 <pre>
215 --enable-ebcdic
216 </pre>
217 to the <b>configure</b> command.
218 </P>
219 <P>
220 Last updated: 06 June 2006
221 <br>
222 Copyright &copy; 1997-2006 University of Cambridge.
223 <p>
224 Return to the <a href="index.html">PCRE index page</a>.
225 </p>

webmaster@exim.org
ViewVC Help
Powered by ViewVC 1.1.12