ViewVC logotype

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

Parent Directory Parent Directory | Revision Log Revision Log

Revision 197 - (hide annotations) (download) (as text)
Tue Jul 31 10:50:18 2007 UTC (7 years, 8 months ago) by ph10
File MIME type: text/html
File size: 11818 byte(s)
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 nigel 63 <html>
2     <head>
3     <title>pcrebuild specification</title>
4     </head>
5     <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 nigel 75 <h1>pcrebuild man page</h1>
7     <p>
8     Return to the <a href="index.html">PCRE index page</a>.
9     </p>
10 ph10 111 <p>
11 nigel 75 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 ph10 111 <br>
15 nigel 63 <ul>
16     <li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a>
17 nigel 83 <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 nigel 91 <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 ph10 128 <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 nigel 63 </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 nigel 75 options to the <b>configure</b> script that is run before the <b>make</b>
37 nigel 63 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 nigel 75 </pre>
43 ph10 128 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 nigel 63 <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 nigel 83 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
50 nigel 63 <P>
51 nigel 83 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 nigel 63 To build PCRE with support for UTF-8 character strings, add
62     <pre>
63     --enable-utf8
64 nigel 75 </pre>
65 nigel 63 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 nigel 83 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
71 nigel 63 <P>
72 nigel 75 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 ph10 128 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 nigel 75 <a href="pcrepattern.html"><b>pcrepattern</b></a>
88     documentation.
89     </P>
90 nigel 83 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
91 nigel 75 <P>
92 nigel 91 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 nigel 63 <pre>
96     --enable-newline-is-cr
97 nigel 75 </pre>
98 nigel 91 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 nigel 93 to the <b>configure</b> command. There is a fourth option, specified by
108     <pre>
109 ph10 150 --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 nigel 93 --enable-newline-is-any
115     </pre>
116 ph10 150 causes PCRE to recognize any Unicode newline sequence.
117 nigel 63 </P>
118 nigel 93 <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 nigel 83 <br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
124 nigel 63 <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 nigel 75 </pre>
131 nigel 63 to the <b>configure</b> command, as required.
132     </P>
133 nigel 83 <br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
134 nigel 63 <P>
135 nigel 75 When PCRE is called through the POSIX interface (see the
136     <a href="pcreposix.html"><b>pcreposix</b></a>
137 nigel 63 documentation), additional working storage is required for holding the pointers
138 nigel 75 to capturing substrings, because PCRE requires three integers per substring,
139 nigel 63 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 nigel 75 </pre>
147 nigel 63 to the <b>configure</b> command.
148     </P>
149 nigel 91 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
150 nigel 63 <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 nigel 75 metacharacter). By default, two-byte values are used for these offsets, leading
154 nigel 63 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 nigel 75 </pre>
161 nigel 63 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 nigel 91 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
166 nigel 63 <P>
167 nigel 77 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 nigel 91 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 nigel 73 <pre>
179     --disable-stack-for-recursion
180 nigel 75 </pre>
181 nigel 73 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 ph10 182 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 nigel 73 </P>
187 ph10 182 <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 nigel 91 <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 ph10 128 <br><a name="SEC11" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
226 nigel 73 <P>
227 ph10 128 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 nigel 73 PCRE assumes by default that it will run in an environment where the character
245 ph10 197 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 nigel 73 <pre>
249     --enable-ebcdic
250 nigel 75 </pre>
251 ph10 128 to the <b>configure</b> command. This setting implies
252 ph10 197 --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 nigel 73 </P>
255 ph10 128 <br><a name="SEC13" href="#TOC1">SEE ALSO</a><br>
256 nigel 73 <P>
257 nigel 93 <b>pcreapi</b>(3), <b>pcre_config</b>(3).
258     </P>
259 ph10 128 <br><a name="SEC14" href="#TOC1">AUTHOR</a><br>
260 nigel 93 <P>
261 ph10 99 Philip Hazel
262 nigel 63 <br>
263 ph10 99 University Computing Service
264     <br>
265     Cambridge CB2 3QH, England.
266     <br>
267     </P>
268 ph10 128 <br><a name="SEC15" href="#TOC1">REVISION</a><br>
269 ph10 99 <P>
270 ph10 197 Last updated: 30 July 2007
271 ph10 99 <br>
272     Copyright &copy; 1997-2007 University of Cambridge.
273     <br>
274 nigel 75 <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 1.1.12