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1 <html>
2 <head>
3 <title>pcrebuild specification</title>
4 </head>
5 <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6 This HTML document has been generated automatically from the original man page.
7 If there is any nonsense in it, please consult the man page, in case the
8 conversion went wrong.<br>
9 <ul>
10 <li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a>
11 <li><a name="TOC2" href="#SEC2">UTF-8 SUPPORT</a>
12 <li><a name="TOC3" href="#SEC3">CODE VALUE OF NEWLINE</a>
13 <li><a name="TOC4" href="#SEC4">BUILDING SHARED AND STATIC LIBRARIES</a>
14 <li><a name="TOC5" href="#SEC5">POSIX MALLOC USAGE</a>
15 <li><a name="TOC6" href="#SEC6">LIMITING PCRE RESOURCE USAGE</a>
16 <li><a name="TOC7" href="#SEC7">HANDLING VERY LARGE PATTERNS</a>
17 <li><a name="TOC8" href="#SEC8">AVOIDING EXCESSIVE STACK USAGE</a>
18 <li><a name="TOC9" href="#SEC9">USING EBCDIC CODE</a>
19 </ul>
20 <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
21 <P>
22 This document describes the optional features of PCRE that can be selected when
23 the library is compiled. They are all selected, or deselected, by providing
24 options to the <b>configure</b> script which is run before the <b>make</b>
25 command. The complete list of options for <b>configure</b> (which includes the
26 standard ones such as the selection of the installation directory) can be
27 obtained by running
28 </P>
29 <P>
30 <pre>
31 ./configure --help
32 </PRE>
33 </P>
34 <P>
35 The following sections describe certain options whose names begin with --enable
36 or --disable. These settings specify changes to the defaults for the
37 <b>configure</b> command. Because of the way that <b>configure</b> works,
38 --enable and --disable always come in pairs, so the complementary option always
39 exists as well, but as it specifies the default, it is not described.
40 </P>
41 <br><a name="SEC2" href="#TOC1">UTF-8 SUPPORT</a><br>
42 <P>
43 To build PCRE with support for UTF-8 character strings, add
44 </P>
45 <P>
46 <pre>
47 --enable-utf8
48 </PRE>
49 </P>
50 <P>
51 to the <b>configure</b> command. Of itself, this does not make PCRE treat
52 strings as UTF-8. As well as compiling PCRE with this option, you also have
53 have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
54 function.
55 </P>
56 <br><a name="SEC3" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
57 <P>
58 By default, PCRE treats character 10 (linefeed) as the newline character. This
59 is the normal newline character on Unix-like systems. You can compile PCRE to
60 use character 13 (carriage return) instead by adding
61 </P>
62 <P>
63 <pre>
64 --enable-newline-is-cr
65 </PRE>
66 </P>
67 <P>
68 to the <b>configure</b> command. For completeness there is also a
69 --enable-newline-is-lf option, which explicitly specifies linefeed as the
70 newline character.
71 </P>
72 <br><a name="SEC4" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
73 <P>
74 The PCRE building process uses <b>libtool</b> to build both shared and static
75 Unix libraries by default. You can suppress one of these by adding one of
76 </P>
77 <P>
78 <pre>
79 --disable-shared
80 --disable-static
81 </PRE>
82 </P>
83 <P>
84 to the <b>configure</b> command, as required.
85 </P>
86 <br><a name="SEC5" href="#TOC1">POSIX MALLOC USAGE</a><br>
87 <P>
88 When PCRE is called through the POSIX interface (see the <b>pcreposix</b>
89 documentation), additional working storage is required for holding the pointers
90 to capturing substrings because PCRE requires three integers per substring,
91 whereas the POSIX interface provides only two. If the number of expected
92 substrings is small, the wrapper function uses space on the stack, because this
93 is faster than using <b>malloc()</b> for each call. The default threshold above
94 which the stack is no longer used is 10; it can be changed by adding a setting
95 such as
96 </P>
97 <P>
98 <pre>
99 --with-posix-malloc-threshold=20
100 </PRE>
101 </P>
102 <P>
103 to the <b>configure</b> command.
104 </P>
105 <br><a name="SEC6" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
106 <P>
107 Internally, PCRE has a function called <b>match()</b> which it calls repeatedly
108 (possibly recursively) when performing a matching operation. By limiting the
109 number of times this function may be called, a limit can be placed on the
110 resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
111 at run time, as described in the <b>pcreapi</b> documentation. The default is 10
112 million, but this can be changed by adding a setting such as
113 </P>
114 <P>
115 <pre>
116 --with-match-limit=500000
117 </PRE>
118 </P>
119 <P>
120 to the <b>configure</b> command.
121 </P>
122 <br><a name="SEC7" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
123 <P>
124 Within a compiled pattern, offset values are used to point from one part to
125 another (for example, from an opening parenthesis to an alternation
126 metacharacter). By default two-byte values are used for these offsets, leading
127 to a maximum size for a compiled pattern of around 64K. This is sufficient to
128 handle all but the most gigantic patterns. Nevertheless, some people do want to
129 process enormous patterns, so it is possible to compile PCRE to use three-byte
130 or four-byte offsets by adding a setting such as
131 </P>
132 <P>
133 <pre>
134 --with-link-size=3
135 </PRE>
136 </P>
137 <P>
138 to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
139 longer offsets slows down the operation of PCRE because it has to load
140 additional bytes when handling them.
141 </P>
142 <P>
143 If you build PCRE with an increased link size, test 2 (and test 5 if you are
144 using UTF-8) will fail. Part of the output of these tests is a representation
145 of the compiled pattern, and this changes with the link size.
146 </P>
147 <br><a name="SEC8" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
148 <P>
149 PCRE implements backtracking while matching by making recursive calls to an
150 internal function called <b>match()</b>. In environments where the size of the
151 stack is limited, this can severely limit PCRE's operation. (The Unix
152 environment does not usually suffer from this problem.) An alternative approach
153 that uses memory from the heap to remember data, instead of using recursive
154 function calls, has been implemented to work round this problem. If you want to
155 build a version of PCRE that works this way, add
156 </P>
157 <P>
158 <pre>
159 --disable-stack-for-recursion
160 </PRE>
161 </P>
162 <P>
163 to the <b>configure</b> command. With this configuration, PCRE will use the
164 <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
165 management functions. Separate functions are provided because the usage is very
166 predictable: the block sizes requested are always the same, and the blocks are
167 always freed in reverse order. A calling program might be able to implement
168 optimized functions that perform better than the standard <b>malloc()</b> and
169 <b>free()</b> functions. PCRE runs noticeably more slowly when built in this
170 way.
171 </P>
172 <br><a name="SEC9" href="#TOC1">USING EBCDIC CODE</a><br>
173 <P>
174 PCRE assumes by default that it will run in an environment where the character
175 code is ASCII (or UTF-8, which is a superset of ASCII). PCRE can, however, be
176 compiled to run in an EBCDIC environment by adding
177 </P>
178 <P>
179 <pre>
180 --enable-ebcdic
181 </PRE>
182 </P>
183 <P>
184 to the <b>configure</b> command.
185 </P>
186 <P>
187 Last updated: 09 December 2003
188 <br>
189 Copyright &copy; 1997-2003 University of Cambridge.

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