/[pcre]/code/trunk/doc/pcrebuild.3
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revision 83 by nigel, Sat Feb 24 21:41:06 2007 UTC revision 195 by ph10, Mon Jul 30 13:23:28 2007 UTC
# Line 13  obtained by running Line 13  obtained by running
13  .sp  .sp
14    ./configure --help    ./configure --help
15  .sp  .sp
16  The following sections describe certain options whose names begin with --enable  The following sections include descriptions of options whose names begin with
17  or --disable. These settings specify changes to the defaults for the  --enable or --disable. These settings specify changes to the defaults for the
18  \fBconfigure\fP command. Because of the way that \fBconfigure\fP works,  \fBconfigure\fP command. Because of the way that \fBconfigure\fP works,
19  --enable and --disable always come in pairs, so the complementary option always  --enable and --disable always come in pairs, so the complementary option always
20  exists as well, but as it specifies the default, it is not described.  exists as well, but as it specifies the default, it is not described.
# Line 56  character properties, you must add Line 56  character properties, you must add
56  to the \fBconfigure\fP command. This implies UTF-8 support, even if you have  to the \fBconfigure\fP command. This implies UTF-8 support, even if you have
57  not explicitly requested it.  not explicitly requested it.
58  .P  .P
59  Including Unicode property support adds around 90K of tables to the PCRE  Including Unicode property support adds around 30K of tables to the PCRE
60  library, approximately doubling its size. Only the general category properties  library. Only the general category properties such as \fILu\fP and \fINd\fP are
61  such as \fILu\fP and \fINd\fP are supported. Details are given in the  supported. Details are given in the
62  .\" HREF  .\" HREF
63  \fBpcrepattern\fP  \fBpcrepattern\fP
64  .\"  .\"
# Line 67  documentation. Line 67  documentation.
67  .SH "CODE VALUE OF NEWLINE"  .SH "CODE VALUE OF NEWLINE"
68  .rs  .rs
69  .sp  .sp
70  By default, PCRE treats character 10 (linefeed) as the newline character. This  By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
71  is the normal newline character on Unix-like systems. You can compile PCRE to  of a line. This is the normal newline character on Unix-like systems. You can
72  use character 13 (carriage return) instead by adding  compile PCRE to use character 13 (carriage return, CR) instead, by adding
73  .sp  .sp
74    --enable-newline-is-cr    --enable-newline-is-cr
75  .sp  .sp
76  to the \fBconfigure\fP command. For completeness there is also a  to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option,
77  --enable-newline-is-lf option, which explicitly specifies linefeed as the  which explicitly specifies linefeed as the newline character.
78  newline character.  .sp
79    Alternatively, you can specify that line endings are to be indicated by the two
80    character sequence CRLF. If you want this, add
81    .sp
82      --enable-newline-is-crlf
83    .sp
84    to the \fBconfigure\fP command. There is a fourth option, specified by
85    .sp
86      --enable-newline-is-anycrlf
87    .sp
88    which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
89    indicating a line ending. Finally, a fifth option, specified by
90    .sp
91      --enable-newline-is-any
92    .sp
93    causes PCRE to recognize any Unicode newline sequence.
94    .P
95    Whatever line ending convention is selected when PCRE is built can be
96    overridden when the library functions are called. At build time it is
97    conventional to use the standard for your operating system.
98  .  .
99  .SH "BUILDING SHARED AND STATIC LIBRARIES"  .SH "BUILDING SHARED AND STATIC LIBRARIES"
100  .rs  .rs
# Line 107  such as Line 126  such as
126  .sp  .sp
127  to the \fBconfigure\fP command.  to the \fBconfigure\fP command.
128  .  .
 .SH "LIMITING PCRE RESOURCE USAGE"  
 .rs  
 .sp  
 Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly  
 (possibly 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.  
 .  
129  .SH "HANDLING VERY LARGE PATTERNS"  .SH "HANDLING VERY LARGE PATTERNS"
130  .rs  .rs
131  .sp  .sp
# Line 143  or four-byte offsets by adding a setting Line 142  or four-byte offsets by adding a setting
142  to the \fBconfigure\fP command. The value given must be 2, 3, or 4. Using  to the \fBconfigure\fP command. The value given must be 2, 3, or 4. Using
143  longer offsets slows down the operation of PCRE because it has to load  longer offsets slows down the operation of PCRE because it has to load
144  additional bytes when handling them.  additional bytes when handling them.
 .P  
 If you build PCRE with an increased link size, test 2 (and test 5 if you are  
 using UTF-8) will fail. Part of the output of these tests is a representation  
 of the compiled pattern, and this changes with the link size.  
145  .  .
146  .SH "AVOIDING EXCESSIVE STACK USAGE"  .SH "AVOIDING EXCESSIVE STACK USAGE"
147  .rs  .rs
# Line 155  When matching with the \fBpcre_exec()\fP Line 150  When matching with the \fBpcre_exec()\fP
150  by making recursive calls to an internal function called \fBmatch()\fP. In  by making recursive calls to an internal function called \fBmatch()\fP. In
151  environments where the size of the stack is limited, this can severely limit  environments where the size of the stack is limited, this can severely limit
152  PCRE's operation. (The Unix environment does not usually suffer from this  PCRE's operation. (The Unix environment does not usually suffer from this
153  problem.) An alternative approach that uses memory from the heap to remember  problem, but it may sometimes be necessary to increase the maximum stack size.
154  data, instead of using recursive function calls, has been implemented to work  There is a discussion in the
155  round this problem. If you want to build a version of PCRE that works this way,  .\" HREF
156  add  \fBpcrestack\fP
157    .\"
158    documentation.) An alternative approach to recursion that uses memory from the
159    heap to remember data, instead of using recursive function calls, has been
160    implemented to work round the problem of limited stack size. If you want to
161    build a version of PCRE that works this way, add
162  .sp  .sp
163    --disable-stack-for-recursion    --disable-stack-for-recursion
164  .sp  .sp
165  to the \fBconfigure\fP command. With this configuration, PCRE will use the  to the \fBconfigure\fP command. With this configuration, PCRE will use the
166  \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory  \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory
167  management functions. Separate functions are provided because the usage is very  management functions. By default these point to \fBmalloc()\fP and
168  predictable: the block sizes requested are always the same, and the blocks are  \fBfree()\fP, but you can replace the pointers so that your own functions are
169  always freed in reverse order. A calling program might be able to implement  used.
170  optimized functions that perform better than the standard \fBmalloc()\fP and  .P
171  \fBfree()\fP functions. PCRE runs noticeably more slowly when built in this  Separate functions are provided rather than using \fBpcre_malloc\fP and
172  way. This option affects only the \fBpcre_exec()\fP function; it is not  \fBpcre_free\fP because the usage is very predictable: the block sizes
173  relevant for the the \fBpcre_dfa_exec()\fP function.  requested are always the same, and the blocks are always freed in reverse
174    order. A calling program might be able to implement optimized functions that
175    perform better than \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more
176    slowly when built in this way. This option affects only the \fBpcre_exec()\fP
177    function; it is not relevant for the the \fBpcre_dfa_exec()\fP function.
178    .
179    .SH "LIMITING PCRE RESOURCE USAGE"
180    .rs
181    .sp
182    Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly
183    (sometimes recursively) when matching a pattern with the \fBpcre_exec()\fP
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 \fBpcre_exec()\fP. The limit can be changed
187    at run time, as described in the
188    .\" HREF
189    \fBpcreapi\fP
190    .\"
191    documentation. The default is 10 million, but this can be changed by adding a
192    setting such as
193    .sp
194      --with-match-limit=500000
195    .sp
196    to the \fBconfigure\fP command. This setting has no effect on the
197    \fBpcre_dfa_exec()\fP matching function.
198    .P
199    In some environments it is desirable to limit the depth of recursive calls of
200    \fBmatch()\fP more strictly than the total number of calls, in order to
201    restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
202    is specified) that is used. A second limit controls this; it defaults to the
203    value that is set for --with-match-limit, which imposes no additional
204    constraints. However, you can set a lower limit by adding, for example,
205    .sp
206      --with-match-limit-recursion=10000
207    .sp
208    to the \fBconfigure\fP command. This value can also be overridden at run time.
209    .
210    .SH "CREATING CHARACTER TABLES AT BUILD TIME"
211    .rs
212    .sp
213    PCRE uses fixed tables for processing characters whose code values are less
214    than 256. By default, PCRE is built with a set of tables that are distributed
215    in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes
216    only. If you add
217    .sp
218      --enable-rebuild-chartables
219    .sp
220    to the \fBconfigure\fP command, the distributed tables are no longer used.
221    Instead, a program called \fBdftables\fP is compiled and run. This outputs the
222    source for new set of tables, created in the default locale of your C runtime
223    system. (This method of replacing the tables does not work if you are cross
224    compiling, because \fBdftables\fP is run on the local host. If you need to
225    create alternative tables when cross compiling, you will have to do so "by
226    hand".)
227  .  .
228  .SH "USING EBCDIC CODE"  .SH "USING EBCDIC CODE"
229  .rs  .rs
230  .sp  .sp
231  PCRE assumes by default that it will run in an environment where the character  PCRE assumes by default that it will run in an environment where the character
232  code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be  code is ASCII (or Unicode, which is a superset of ASCII). This is the case for
233  compiled to run in an EBCDIC environment by adding  most computer operating systems. PCRE can, however, be compiled to run in an
234    EBCDIC environment by adding
235  .sp  .sp
236    --enable-ebcdic    --enable-ebcdic
237  .sp  .sp
238  to the \fBconfigure\fP command.  to the \fBconfigure\fP command. This setting implies
239  .P  --enable-rebuild-chartables. You should only use it if you know that you are in
240  .in 0  an EBCDIC environment (for example, an IBM mainframe operating system).
241  Last updated: 15 August 2005  .
242  .br  .
243  Copyright (c) 1997-2005 University of Cambridge.  .SH "SEE ALSO"
244    .rs
245    .sp
246    \fBpcreapi\fP(3), \fBpcre_config\fP(3).
247    .
248    .
249    .SH AUTHOR
250    .rs
251    .sp
252    .nf
253    Philip Hazel
254    University Computing Service
255    Cambridge CB2 3QH, England.
256    .fi
257    .
258    .
259    .SH REVISION
260    .rs
261    .sp
262    .nf
263    Last updated: 30 July 2007
264    Copyright (c) 1997-2007 University of Cambridge.
265    .fi

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