trunk/doc/pcrebuild.3

.TH PCREBUILD 3
.SH NAME
PCRE - Perl-compatible regular expressions
.SH "PCRE BUILD-TIME OPTIONS"
.rs
.sp
This document describes the optional features of PCRE that can be selected when
the library is compiled. It assumes use of the \fBconfigure\fP script, where
the optional features are selected or deselected by providing options to
\fBconfigure\fP before running the \fBmake\fP command. However, the same
options can be selected in both Unix-like and non-Unix-like environments using
the GUI facility of \fBCMakeSetup\fP if you are using \fBCMake\fP instead of
\fBconfigure\fP to build PCRE.
.P
The complete list of options for \fBconfigure\fP (which includes the standard
ones such as the selection of the installation directory) can be obtained by
running
.sp
  ./configure --help
.sp
The following sections include descriptions of options whose names begin with
--enable or --disable. These settings specify changes to the defaults for the
\fBconfigure\fP command. Because of the way that \fBconfigure\fP works,
--enable and --disable always come in pairs, so the complementary option always
exists as well, but as it specifies the default, it is not described.
.
.SH "C++ SUPPORT"
.rs
.sp
By default, the \fBconfigure\fP script will search for a C++ compiler and C++
header files. If it finds them, it automatically builds the C++ wrapper library
for PCRE. You can disable this by adding
.sp
  --disable-cpp
.sp
to the \fBconfigure\fP command.
.
.SH "UTF-8 SUPPORT"
.rs
.sp
To build PCRE with support for UTF-8 character strings, add
.sp
  --enable-utf8
.sp
to the \fBconfigure\fP command. Of itself, this does not make PCRE treat
strings as UTF-8. As well as compiling PCRE with this option, you also have
have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fP
function.
.
.SH "UNICODE CHARACTER PROPERTY SUPPORT"
.rs
.sp
UTF-8 support allows PCRE to process character values greater than 255 in the
strings that it handles. On its own, however, it does not provide any
facilities for accessing the properties of such characters. If you want to be
able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode
character properties, you must add
.sp
  --enable-unicode-properties
.sp
to the \fBconfigure\fP command. This implies UTF-8 support, even if you have
not explicitly requested it.
.P
Including Unicode property support adds around 30K of tables to the PCRE
library. Only the general category properties such as \fILu\fP and \fINd\fP are
supported. Details are given in the
.\" HREF
\fBpcrepattern\fP
.\"
documentation.
.
.SH "CODE VALUE OF NEWLINE"
.rs
.sp
By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
of a line. This is the normal newline character on Unix-like systems. You can
compile PCRE to use character 13 (carriage return, CR) instead, by adding
.sp
  --enable-newline-is-cr
.sp
to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option,
which explicitly specifies linefeed as the newline character.
.sp
Alternatively, you can specify that line endings are to be indicated by the two
character sequence CRLF. If you want this, add
.sp
  --enable-newline-is-crlf
.sp
to the \fBconfigure\fP command. There is a fourth option, specified by
.sp
  --enable-newline-is-anycrlf
.sp
which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
indicating a line ending. Finally, a fifth option, specified by
.sp
  --enable-newline-is-any
.sp
causes PCRE to recognize any Unicode newline sequence.
.P
Whatever line ending convention is selected when PCRE is built can be
overridden when the library functions are called. At build time it is
conventional to use the standard for your operating system.
.
.SH "WHAT \eR MATCHES"
.rs
.sp
By default, the sequence \eR in a pattern matches any Unicode newline sequence,
whatever has been selected as the line ending sequence. If you specify
.sp
  --enable-bsr-anycrlf
.sp
the default is changed so that \eR matches only CR, LF, or CRLF. Whatever is
selected when PCRE is built can be overridden when the library functions are
called.
.
.SH "BUILDING SHARED AND STATIC LIBRARIES"
.rs
.sp
The PCRE building process uses \fBlibtool\fP to build both shared and static
Unix libraries by default. You can suppress one of these by adding one of
.sp
  --disable-shared
  --disable-static
.sp
to the \fBconfigure\fP command, as required.
.
.SH "POSIX MALLOC USAGE"
.rs
.sp
When PCRE is called through the POSIX interface (see the
.\" HREF
\fBpcreposix\fP
.\"
documentation), additional working storage is required for holding the pointers
to capturing substrings, because PCRE requires three integers per substring,
whereas the POSIX interface provides only two. If the number of expected
substrings is small, the wrapper function uses space on the stack, because this
is faster than using \fBmalloc()\fP for each call. The default threshold above
which the stack is no longer used is 10; it can be changed by adding a setting
such as
.sp
  --with-posix-malloc-threshold=20
.sp
to the \fBconfigure\fP command.
.
.SH "HANDLING VERY LARGE PATTERNS"
.rs
.sp
Within a compiled pattern, offset values are used to point from one part to
another (for example, from an opening parenthesis to an alternation
metacharacter). By default, two-byte values are used for these offsets, leading
to a maximum size for a compiled pattern of around 64K. This is sufficient to
handle all but the most gigantic patterns. Nevertheless, some people do want to
process enormous patterns, so it is possible to compile PCRE to use three-byte
or four-byte offsets by adding a setting such as
.sp
  --with-link-size=3
.sp
to the \fBconfigure\fP command. The value given must be 2, 3, or 4. Using
longer offsets slows down the operation of PCRE because it has to load
additional bytes when handling them.
.
.SH "AVOIDING EXCESSIVE STACK USAGE"
.rs
.sp
When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking
by making recursive calls to an internal function called \fBmatch()\fP. In
environments where the size of the stack is limited, this can severely limit
PCRE's operation. (The Unix environment does not usually suffer from this
problem, but it may sometimes be necessary to increase the maximum stack size.
There is a discussion in the
.\" HREF
\fBpcrestack\fP
.\"
documentation.) An alternative approach to recursion that uses memory from the
heap to remember data, instead of using recursive function calls, has been
implemented to work round the problem of limited stack size. If you want to
build a version of PCRE that works this way, add
.sp
  --disable-stack-for-recursion
.sp
to the \fBconfigure\fP command. With this configuration, PCRE will use the
\fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory
management functions. By default these point to \fBmalloc()\fP and
\fBfree()\fP, but you can replace the pointers so that your own functions are
used.
.P
Separate functions are provided rather than using \fBpcre_malloc\fP and
\fBpcre_free\fP because the usage is very predictable: the block sizes
requested are always the same, and the blocks are always freed in reverse
order. A calling program might be able to implement optimized functions that
perform better than \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more
slowly when built in this way. This option affects only the \fBpcre_exec()\fP
function; it is not relevant for the the \fBpcre_dfa_exec()\fP function.
.
.SH "LIMITING PCRE RESOURCE USAGE"
.rs
.sp
Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly
(sometimes recursively) when matching a pattern with the \fBpcre_exec()\fP
function. By controlling the maximum number of times this function may be
called during a single matching operation, a limit can be placed on the
resources used by a single call to \fBpcre_exec()\fP. The limit can be changed
at run time, as described in the
.\" HREF
\fBpcreapi\fP
.\"
documentation. The default is 10 million, but this can be changed by adding a
setting such as
.sp
  --with-match-limit=500000
.sp
to the \fBconfigure\fP command. This setting has no effect on the
\fBpcre_dfa_exec()\fP matching function.
.P
In some environments it is desirable to limit the depth of recursive calls of
\fBmatch()\fP more strictly than the total number of calls, in order to
restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
is specified) that is used. A second limit controls this; it defaults to the
value that is set for --with-match-limit, which imposes no additional
constraints. However, you can set a lower limit by adding, for example,
.sp
  --with-match-limit-recursion=10000
.sp
to the \fBconfigure\fP command. This value can also be overridden at run time.
.
.SH "CREATING CHARACTER TABLES AT BUILD TIME"
.rs
.sp
PCRE uses fixed tables for processing characters whose code values are less
than 256. By default, PCRE is built with a set of tables that are distributed
in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes
only. If you add
.sp
  --enable-rebuild-chartables
.sp
to the \fBconfigure\fP command, the distributed tables are no longer used.
Instead, a program called \fBdftables\fP is compiled and run. This outputs the
source for new set of tables, created in the default locale of your C runtime
system. (This method of replacing the tables does not work if you are cross
compiling, because \fBdftables\fP is run on the local host. If you need to
create alternative tables when cross compiling, you will have to do so "by
hand".)
.
.SH "USING EBCDIC CODE"
.rs
.sp
PCRE assumes by default that it will run in an environment where the character
code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
most computer operating systems. PCRE can, however, be compiled to run in an
EBCDIC environment by adding
.sp
  --enable-ebcdic
.sp
to the \fBconfigure\fP command. This setting implies
--enable-rebuild-chartables. You should only use it if you know that you are in
an EBCDIC environment (for example, an IBM mainframe operating system).
.
.SH "PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT"
.rs
.sp
By default, \fBpcregrep\fP reads all files as plain text. You can build it so
that it recognizes files whose names end in \fB.gz\fP or \fB.bz2\fP, and reads
them with \fBlibz\fP or \fBlibbz2\fP, respectively, by adding one or both of
.sp
  --enable-pcregrep-libz
  --enable-pcregrep-libbz2
.sp
to the \fBconfigure\fP command. These options naturally require that the
relevant libraries are installed on your system. Configuration will fail if
they are not.
.
.SH "PCRETEST OPTION FOR LIBREADLINE SUPPORT"
.rs
.sp
If you add
.sp
  --enable-pcretest-libreadline
.sp
to the \fBconfigure\fP command, \fBpcretest\fP is linked with the 
\fBlibreadline\fP library, and when its input is from a terminal, it reads it 
using the \fBreadline()\fP function. This provides line-editing and history 
facilities. Note that \fBlibreadline\fP is GPL-licenced, so if you distribute a 
binary of \fBpcretest\fP linked in this way, there may be licensing issues.
.
.
.SH "SEE ALSO"
.rs
.sp
\fBpcreapi\fP(3), \fBpcre_config\fP(3).
.
.
.SH AUTHOR
.rs
.sp
.nf
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
.fi
.
.
.SH REVISION
.rs
.sp
.nf
Last updated: 18 December 2007
Copyright (c) 1997-2007 University of Cambridge.
.fi
1	.TH PCREBUILD 3
2	.SH NAME
3	PCRE - Perl-compatible regular expressions
4	.SH "PCRE BUILD-TIME OPTIONS"
5	.rs
6	.sp
7	This document describes the optional features of PCRE that can be selected when
8	the library is compiled. It assumes use of the \fBconfigure\fP script, where
9	the optional features are selected or deselected by providing options to
10	\fBconfigure\fP before running the \fBmake\fP command. However, the same
11	options can be selected in both Unix-like and non-Unix-like environments using
12	the GUI facility of \fBCMakeSetup\fP if you are using \fBCMake\fP instead of
13	\fBconfigure\fP to build PCRE.
14	.P
15	The complete list of options for \fBconfigure\fP (which includes the standard
16	ones such as the selection of the installation directory) can be obtained by
17	running
18	.sp
19	./configure --help
20	.sp
21	The following sections include descriptions of options whose names begin with
22	--enable or --disable. These settings specify changes to the defaults for the
23	\fBconfigure\fP command. Because of the way that \fBconfigure\fP works,
24	--enable and --disable always come in pairs, so the complementary option always
25	exists as well, but as it specifies the default, it is not described.
26	.
27	.SH "C++ SUPPORT"
28	.rs
29	.sp
30	By default, the \fBconfigure\fP script will search for a C++ compiler and C++
31	header files. If it finds them, it automatically builds the C++ wrapper library
32	for PCRE. You can disable this by adding
33	.sp
34	--disable-cpp
35	.sp
36	to the \fBconfigure\fP command.
37	.
38	.SH "UTF-8 SUPPORT"
39	.rs
40	.sp
41	To build PCRE with support for UTF-8 character strings, add
42	.sp
43	--enable-utf8
44	.sp
45	to the \fBconfigure\fP command. Of itself, this does not make PCRE treat
46	strings as UTF-8. As well as compiling PCRE with this option, you also have
47	have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fP
48	function.
49	.
50	.SH "UNICODE CHARACTER PROPERTY SUPPORT"
51	.rs
52	.sp
53	UTF-8 support allows PCRE to process character values greater than 255 in the
54	strings that it handles. On its own, however, it does not provide any
55	facilities for accessing the properties of such characters. If you want to be
56	able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode
57	character properties, you must add
58	.sp
59	--enable-unicode-properties
60	.sp
61	to the \fBconfigure\fP command. This implies UTF-8 support, even if you have
62	not explicitly requested it.
63	.P
64	Including Unicode property support adds around 30K of tables to the PCRE
65	library. Only the general category properties such as \fILu\fP and \fINd\fP are
66	supported. Details are given in the
67	.\" HREF
68	\fBpcrepattern\fP
69	.\"
70	documentation.
71	.
72	.SH "CODE VALUE OF NEWLINE"
73	.rs
74	.sp
75	By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
76	of a line. This is the normal newline character on Unix-like systems. You can
77	compile PCRE to use character 13 (carriage return, CR) instead, by adding
78	.sp
79	--enable-newline-is-cr
80	.sp
81	to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option,
82	which explicitly specifies linefeed as the newline character.
83	.sp
84	Alternatively, you can specify that line endings are to be indicated by the two
85	character sequence CRLF. If you want this, add
86	.sp
87	--enable-newline-is-crlf
88	.sp
89	to the \fBconfigure\fP command. There is a fourth option, specified by
90	.sp
91	--enable-newline-is-anycrlf
92	.sp
93	which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
94	indicating a line ending. Finally, a fifth option, specified by
95	.sp
96	--enable-newline-is-any
97	.sp
98	causes PCRE to recognize any Unicode newline sequence.
99	.P
100	Whatever line ending convention is selected when PCRE is built can be
101	overridden when the library functions are called. At build time it is
102	conventional to use the standard for your operating system.
103	.
104	.SH "WHAT \eR MATCHES"
105	.rs
106	.sp
107	By default, the sequence \eR in a pattern matches any Unicode newline sequence,
108	whatever has been selected as the line ending sequence. If you specify
109	.sp
110	--enable-bsr-anycrlf
111	.sp
112	the default is changed so that \eR matches only CR, LF, or CRLF. Whatever is
113	selected when PCRE is built can be overridden when the library functions are
114	called.
115	.
116	.SH "BUILDING SHARED AND STATIC LIBRARIES"
117	.rs
118	.sp
119	The PCRE building process uses \fBlibtool\fP to build both shared and static
120	Unix libraries by default. You can suppress one of these by adding one of
121	.sp
122	--disable-shared
123	--disable-static
124	.sp
125	to the \fBconfigure\fP command, as required.
126	.
127	.SH "POSIX MALLOC USAGE"
128	.rs
129	.sp
130	When PCRE is called through the POSIX interface (see the
131	.\" HREF
132	\fBpcreposix\fP
133	.\"
134	documentation), additional working storage is required for holding the pointers
135	to capturing substrings, because PCRE requires three integers per substring,
136	whereas the POSIX interface provides only two. If the number of expected
137	substrings is small, the wrapper function uses space on the stack, because this
138	is faster than using \fBmalloc()\fP for each call. The default threshold above
139	which the stack is no longer used is 10; it can be changed by adding a setting
140	such as
141	.sp
142	--with-posix-malloc-threshold=20
143	.sp
144	to the \fBconfigure\fP command.
145	.
146	.SH "HANDLING VERY LARGE PATTERNS"
147	.rs
148	.sp
149	Within a compiled pattern, offset values are used to point from one part to
150	another (for example, from an opening parenthesis to an alternation
151	metacharacter). By default, two-byte values are used for these offsets, leading
152	to a maximum size for a compiled pattern of around 64K. This is sufficient to
153	handle all but the most gigantic patterns. Nevertheless, some people do want to
154	process enormous patterns, so it is possible to compile PCRE to use three-byte
155	or four-byte offsets by adding a setting such as
156	.sp
157	--with-link-size=3
158	.sp
159	to the \fBconfigure\fP command. The value given must be 2, 3, or 4. Using
160	longer offsets slows down the operation of PCRE because it has to load
161	additional bytes when handling them.
162	.
163	.SH "AVOIDING EXCESSIVE STACK USAGE"
164	.rs
165	.sp
166	When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking
167	by making recursive calls to an internal function called \fBmatch()\fP. In
168	environments where the size of the stack is limited, this can severely limit
169	PCRE's operation. (The Unix environment does not usually suffer from this
170	problem, but it may sometimes be necessary to increase the maximum stack size.
171	There is a discussion in the
172	.\" HREF
173	\fBpcrestack\fP
174	.\"
175	documentation.) An alternative approach to recursion that uses memory from the
176	heap to remember data, instead of using recursive function calls, has been
177	implemented to work round the problem of limited stack size. If you want to
178	build a version of PCRE that works this way, add
179	.sp
180	--disable-stack-for-recursion
181	.sp
182	to the \fBconfigure\fP command. With this configuration, PCRE will use the
183	\fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory
184	management functions. By default these point to \fBmalloc()\fP and
185	\fBfree()\fP, but you can replace the pointers so that your own functions are
186	used.
187	.P
188	Separate functions are provided rather than using \fBpcre_malloc\fP and
189	\fBpcre_free\fP 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 \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more
193	slowly when built in this way. This option affects only the \fBpcre_exec()\fP
194	function; it is not relevant for the the \fBpcre_dfa_exec()\fP function.
195	.
196	.SH "LIMITING PCRE RESOURCE USAGE"
197	.rs
198	.sp
199	Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly
200	(sometimes recursively) when matching a pattern with the \fBpcre_exec()\fP
201	function. By controlling the maximum number of times this function may be
202	called during a single matching operation, a limit can be placed on the
203	resources used by a single call to \fBpcre_exec()\fP. The limit can be changed
204	at run time, as described in the
205	.\" HREF
206	\fBpcreapi\fP
207	.\"
208	documentation. The default is 10 million, but this can be changed by adding a
209	setting such as
210	.sp
211	--with-match-limit=500000
212	.sp
213	to the \fBconfigure\fP command. This setting has no effect on the
214	\fBpcre_dfa_exec()\fP matching function.
215	.P
216	In some environments it is desirable to limit the depth of recursive calls of
217	\fBmatch()\fP more strictly than the total number of calls, in order to
218	restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
219	is specified) that is used. A second limit controls this; it defaults to the
220	value that is set for --with-match-limit, which imposes no additional
221	constraints. However, you can set a lower limit by adding, for example,
222	.sp
223	--with-match-limit-recursion=10000
224	.sp
225	to the \fBconfigure\fP command. This value can also be overridden at run time.
226	.
227	.SH "CREATING CHARACTER TABLES AT BUILD TIME"
228	.rs
229	.sp
230	PCRE uses fixed tables for processing characters whose code values are less
231	than 256. By default, PCRE is built with a set of tables that are distributed
232	in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes
233	only. If you add
234	.sp
235	--enable-rebuild-chartables
236	.sp
237	to the \fBconfigure\fP command, the distributed tables are no longer used.
238	Instead, a program called \fBdftables\fP is compiled and run. This outputs the
239	source for new set of tables, created in the default locale of your C runtime
240	system. (This method of replacing the tables does not work if you are cross
241	compiling, because \fBdftables\fP is run on the local host. If you need to
242	create alternative tables when cross compiling, you will have to do so "by
243	hand".)
244	.
245	.SH "USING EBCDIC CODE"
246	.rs
247	.sp
248	PCRE assumes by default that it will run in an environment where the character
249	code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
250	most computer operating systems. PCRE can, however, be compiled to run in an
251	EBCDIC environment by adding
252	.sp
253	--enable-ebcdic
254	.sp
255	to the \fBconfigure\fP command. This setting implies
256	--enable-rebuild-chartables. You should only use it if you know that you are in
257	an EBCDIC environment (for example, an IBM mainframe operating system).
258	.
259	.SH "PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT"
260	.rs
261	.sp
262	By default, \fBpcregrep\fP reads all files as plain text. You can build it so
263	that it recognizes files whose names end in \fB.gz\fP or \fB.bz2\fP, and reads
264	them with \fBlibz\fP or \fBlibbz2\fP, respectively, by adding one or both of
265	.sp
266	--enable-pcregrep-libz
267	--enable-pcregrep-libbz2
268	.sp
269	to the \fBconfigure\fP command. These options naturally require that the
270	relevant libraries are installed on your system. Configuration will fail if
271	they are not.
272	.
273	.SH "PCRETEST OPTION FOR LIBREADLINE SUPPORT"
274	.rs
275	.sp
276	If you add
277	.sp
278	--enable-pcretest-libreadline
279	.sp
280	to the \fBconfigure\fP command, \fBpcretest\fP is linked with the
281	\fBlibreadline\fP library, and when its input is from a terminal, it reads it
282	using the \fBreadline()\fP function. This provides line-editing and history
283	facilities. Note that \fBlibreadline\fP is GPL-licenced, so if you distribute a
284	binary of \fBpcretest\fP linked in this way, there may be licensing issues.
285	.
286	.
287	.SH "SEE ALSO"
288	.rs
289	.sp
290	\fBpcreapi\fP(3), \fBpcre_config\fP(3).
291	.
292	.
293	.SH AUTHOR
294	.rs
295	.sp
296	.nf
297	Philip Hazel
298	University Computing Service
299	Cambridge CB2 3QH, England.
300	.fi
301	.
302	.
303	.SH REVISION
304	.rs
305	.sp
306	.nf
307	Last updated: 18 December 2007
308	Copyright (c) 1997-2007 University of Cambridge.
309	.fi
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