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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     <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 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 nigel 83 <li><a name="TOC11" href="#SEC11">USING EBCDIC CODE</a>
27 nigel 63 </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 nigel 75 options to the <b>configure</b> script that is run before the <b>make</b>
33 nigel 63 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 nigel 75 </pre>
39 nigel 63 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 nigel 83 <br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
46 nigel 63 <P>
47 nigel 83 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 nigel 63 To build PCRE with support for UTF-8 character strings, add
58     <pre>
59     --enable-utf8
60 nigel 75 </pre>
61 nigel 63 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 nigel 83 <br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
67 nigel 63 <P>
68 nigel 75 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 nigel 83 <br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
87 nigel 75 <P>
88 nigel 91 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 nigel 63 <pre>
92     --enable-newline-is-cr
93 nigel 75 </pre>
94 nigel 91 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 nigel 63 </P>
107 nigel 83 <br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
108 nigel 63 <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 nigel 75 </pre>
115 nigel 63 to the <b>configure</b> command, as required.
116     </P>
117 nigel 83 <br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
118 nigel 63 <P>
119 nigel 75 When PCRE is called through the POSIX interface (see the
120     <a href="pcreposix.html"><b>pcreposix</b></a>
121 nigel 63 documentation), additional working storage is required for holding the pointers
122 nigel 75 to capturing substrings, because PCRE requires three integers per substring,
123 nigel 63 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 nigel 75 </pre>
131 nigel 63 to the <b>configure</b> command.
132     </P>
133 nigel 91 <br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
134 nigel 63 <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 nigel 75 metacharacter). By default, two-byte values are used for these offsets, leading
138 nigel 63 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 nigel 75 </pre>
145 nigel 63 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 nigel 91 <br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
155 nigel 63 <P>
156 nigel 77 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 nigel 91 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 nigel 73 <pre>
168     --disable-stack-for-recursion
169 nigel 75 </pre>
170 nigel 73 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 nigel 77 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 nigel 73 </P>
180 nigel 91 <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 nigel 83 <br><a name="SEC11" href="#TOC1">USING EBCDIC CODE</a><br>
210 nigel 73 <P>
211     PCRE assumes by default that it will run in an environment where the character
212 nigel 75 code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
213 nigel 73 compiled to run in an EBCDIC environment by adding
214     <pre>
215     --enable-ebcdic
216 nigel 75 </pre>
217 nigel 73 to the <b>configure</b> command.
218     </P>
219     <P>
220 nigel 91 Last updated: 06 June 2006
221 nigel 63 <br>
222 nigel 91 Copyright &copy; 1997-2006 University of Cambridge.
223 nigel 75 <p>
224     Return to the <a href="index.html">PCRE index page</a>.
225     </p>

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