/[pcre]/code/trunk/doc/pcrebuild.3
ViewVC logotype

Diff of /code/trunk/doc/pcrebuild.3

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 73 by nigel, Sat Feb 24 21:40:30 2007 UTC revision 83 by nigel, Sat Feb 24 21:41:06 2007 UTC
# Line 1  Line 1 
1  .TH PCRE 3  .TH PCREBUILD 3
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH PCRE BUILD-TIME OPTIONS  .SH "PCRE BUILD-TIME OPTIONS"
5  .rs  .rs
6  .sp  .sp
7  This document describes the optional features of PCRE that can be selected when  This document describes the optional features of PCRE that can be selected when
8  the library is compiled. They are all selected, or deselected, by providing  the library is compiled. They are all selected, or deselected, by providing
9  options to the \fBconfigure\fR script which is run before the \fBmake\fR  options to the \fBconfigure\fP script that is run before the \fBmake\fP
10  command. The complete list of options for \fBconfigure\fR (which includes the  command. The complete list of options for \fBconfigure\fP (which includes the
11  standard ones such as the selection of the installation directory) can be  standard ones such as the selection of the installation directory) can be
12  obtained by running  obtained by running
13    .sp
14    ./configure --help    ./configure --help
15    .sp
16  The following sections describe certain options whose names begin with --enable  The following sections describe certain options whose names begin with --enable
17  or --disable. These settings specify changes to the defaults for the  or --disable. These settings specify changes to the defaults for the
18  \fBconfigure\fR command. Because of the way that \fBconfigure\fR 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.
21    .
22  .SH UTF-8 SUPPORT  .SH "C++ SUPPORT"
23    .rs
24    .sp
25    By default, the \fBconfigure\fP script will search for a C++ compiler and C++
26    header files. If it finds them, it automatically builds the C++ wrapper library
27    for PCRE. You can disable this by adding
28    .sp
29      --disable-cpp
30    .sp
31    to the \fBconfigure\fP command.
32    .
33    .SH "UTF-8 SUPPORT"
34  .rs  .rs
35  .sp  .sp
36  To build PCRE with support for UTF-8 character strings, add  To build PCRE with support for UTF-8 character strings, add
37    .sp
38    --enable-utf8    --enable-utf8
39    .sp
40  to the \fBconfigure\fR command. Of itself, this does not make PCRE treat  to the \fBconfigure\fP command. Of itself, this does not make PCRE treat
41  strings as UTF-8. As well as compiling PCRE with this option, you also have  strings as UTF-8. As well as compiling PCRE with this option, you also have
42  have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fR  have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fP
43  function.  function.
44    .
45  .SH CODE VALUE OF NEWLINE  .SH "UNICODE CHARACTER PROPERTY SUPPORT"
46    .rs
47    .sp
48    UTF-8 support allows PCRE to process character values greater than 255 in the
49    strings that it handles. On its own, however, it does not provide any
50    facilities for accessing the properties of such characters. If you want to be
51    able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode
52    character properties, you must add
53    .sp
54      --enable-unicode-properties
55    .sp
56    to the \fBconfigure\fP command. This implies UTF-8 support, even if you have
57    not explicitly requested it.
58    .P
59    Including Unicode property support adds around 90K of tables to the PCRE
60    library, approximately doubling its size. Only the general category properties
61    such as \fILu\fP and \fINd\fP are supported. Details are given in the
62    .\" HREF
63    \fBpcrepattern\fP
64    .\"
65    documentation.
66    .
67    .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 treats character 10 (linefeed) as the newline character. This
71  is the normal newline character on Unix-like systems. You can compile PCRE to  is the normal newline character on Unix-like systems. You can compile PCRE to
72  use character 13 (carriage return) instead by adding  use character 13 (carriage return) instead by adding
73    .sp
74    --enable-newline-is-cr    --enable-newline-is-cr
75    .sp
76  to the \fBconfigure\fR command. For completeness there is also a  to the \fBconfigure\fP command. For completeness there is also a
77  --enable-newline-is-lf option, which explicitly specifies linefeed as the  --enable-newline-is-lf option, which explicitly specifies linefeed as the
78  newline character.  newline character.
79    .
80  .SH BUILDING SHARED AND STATIC LIBRARIES  .SH "BUILDING SHARED AND STATIC LIBRARIES"
81  .rs  .rs
82  .sp  .sp
83  The PCRE building process uses \fBlibtool\fR to build both shared and static  The PCRE building process uses \fBlibtool\fP to build both shared and static
84  Unix libraries by default. You can suppress one of these by adding one of  Unix libraries by default. You can suppress one of these by adding one of
85    .sp
86    --disable-shared    --disable-shared
87    --disable-static    --disable-static
88    .sp
89  to the \fBconfigure\fR command, as required.  to the \fBconfigure\fP command, as required.
90    .
91  .SH POSIX MALLOC USAGE  .SH "POSIX MALLOC USAGE"
92  .rs  .rs
93  .sp  .sp
94  When PCRE is called through the POSIX interface (see the \fBpcreposix\fR  When PCRE is called through the POSIX interface (see the
95    .\" HREF
96    \fBpcreposix\fP
97    .\"
98  documentation), additional working storage is required for holding the pointers  documentation), additional working storage is required for holding the pointers
99  to capturing substrings because PCRE requires three integers per substring,  to capturing substrings, because PCRE requires three integers per substring,
100  whereas the POSIX interface provides only two. If the number of expected  whereas the POSIX interface provides only two. If the number of expected
101  substrings is small, the wrapper function uses space on the stack, because this  substrings is small, the wrapper function uses space on the stack, because this
102  is faster than using \fBmalloc()\fR for each call. The default threshold above  is faster than using \fBmalloc()\fP for each call. The default threshold above
103  which the stack is no longer used is 10; it can be changed by adding a setting  which the stack is no longer used is 10; it can be changed by adding a setting
104  such as  such as
105    .sp
106    --with-posix-malloc-threshold=20    --with-posix-malloc-threshold=20
   
 to the \fBconfigure\fR command.  
   
 .SH LIMITING PCRE RESOURCE USAGE  
 .rs  
107  .sp  .sp
108  Internally, PCRE has a function called \fBmatch()\fR which it calls repeatedly  to the \fBconfigure\fP command.
109  (possibly recursively) when performing a matching operation. By limiting the  .
110  number of times this function may be called, a limit can be placed on the  .SH "LIMITING PCRE RESOURCE USAGE"
111  resources used by a single call to \fBpcre_exec()\fR. The limit can be changed  .rs
112  at run time, as described in the \fBpcreapi\fR documentation. The default is 10  .sp
113  million, but this can be changed by adding a setting such as  Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly
114    (possibly recursively) when matching a pattern with the \fBpcre_exec()\fP
115    function. By controlling the maximum number of times this function may be
116    called during a single matching operation, a limit can be placed on the
117    resources used by a single call to \fBpcre_exec()\fP. The limit can be changed
118    at run time, as described in the
119    .\" HREF
120    \fBpcreapi\fP
121    .\"
122    documentation. The default is 10 million, but this can be changed by adding a
123    setting such as
124    .sp
125    --with-match-limit=500000    --with-match-limit=500000
126    .sp
127  to the \fBconfigure\fR command.  to the \fBconfigure\fP command. This setting has no effect on the
128    \fBpcre_dfa_exec()\fP matching function.
129  .SH HANDLING VERY LARGE PATTERNS  .
130    .SH "HANDLING VERY LARGE PATTERNS"
131  .rs  .rs
132  .sp  .sp
133  Within a compiled pattern, offset values are used to point from one part to  Within a compiled pattern, offset values are used to point from one part to
134  another (for example, from an opening parenthesis to an alternation  another (for example, from an opening parenthesis to an alternation
135  metacharacter). By default two-byte values are used for these offsets, leading  metacharacter). By default, two-byte values are used for these offsets, leading
136  to a maximum size for a compiled pattern of around 64K. This is sufficient to  to a maximum size for a compiled pattern of around 64K. This is sufficient to
137  handle all but the most gigantic patterns. Nevertheless, some people do want to  handle all but the most gigantic patterns. Nevertheless, some people do want to
138  process enormous patterns, so it is possible to compile PCRE to use three-byte  process enormous patterns, so it is possible to compile PCRE to use three-byte
139  or four-byte offsets by adding a setting such as  or four-byte offsets by adding a setting such as
140    .sp
141    --with-link-size=3    --with-link-size=3
142    .sp
143  to the \fBconfigure\fR 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
144  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
145  additional bytes when handling them.  additional bytes when handling them.
146    .P
147  If you build PCRE with an increased link size, test 2 (and test 5 if you are  If you build PCRE with an increased link size, test 2 (and test 5 if you are
148  using UTF-8) will fail. Part of the output of these tests is a representation  using UTF-8) will fail. Part of the output of these tests is a representation
149  of the compiled pattern, and this changes with the link size.  of the compiled pattern, and this changes with the link size.
150    .
151  .SH AVOIDING EXCESSIVE STACK USAGE  .SH "AVOIDING EXCESSIVE STACK USAGE"
152  .rs  .rs
153  .sp  .sp
154  PCRE implements backtracking while matching by making recursive calls to an  When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking
155  internal function called \fBmatch()\fR. In environments where the size of the  by making recursive calls to an internal function called \fBmatch()\fP. In
156  stack is limited, this can severely limit PCRE's operation. (The Unix  environments where the size of the stack is limited, this can severely limit
157  environment does not usually suffer from this problem.) An alternative approach  PCRE's operation. (The Unix environment does not usually suffer from this
158  that uses memory from the heap to remember data, instead of using recursive  problem.) An alternative approach that uses memory from the heap to remember
159  function calls, has been implemented to work round this problem. If you want to  data, instead of using recursive function calls, has been implemented to work
160  build a version of PCRE that works this way, add  round this problem. If you want to build a version of PCRE that works this way,
161    add
162    .sp
163    --disable-stack-for-recursion    --disable-stack-for-recursion
164    .sp
165  to the \fBconfigure\fR command. With this configuration, PCRE will use the  to the \fBconfigure\fP command. With this configuration, PCRE will use the
166  \fBpcre_stack_malloc\fR and \fBpcre_stack_free\fR 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. Separate functions are provided because the usage is very
168  predictable: the block sizes requested are always the same, and the blocks are  predictable: the block sizes requested are always the same, and the blocks are
169  always freed in reverse order. A calling program might be able to implement  always freed in reverse order. A calling program might be able to implement
170  optimized functions that perform better than the standard \fBmalloc()\fR and  optimized functions that perform better than the standard \fBmalloc()\fP and
171  \fBfree()\fR functions. PCRE runs noticeably more slowly when built in this  \fBfree()\fP functions. PCRE runs noticeably more slowly when built in this
172  way.  way. This option affects only the \fBpcre_exec()\fP function; it is not
173    relevant for the the \fBpcre_dfa_exec()\fP function.
174  .SH USING EBCDIC CODE  .
175    .SH "USING EBCDIC CODE"
176  .rs  .rs
177  .sp  .sp
178  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
179  code is ASCII (or UTF-8, which is a superset of ASCII). PCRE can, however, be  code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
180  compiled to run in an EBCDIC environment by adding  compiled to run in an EBCDIC environment by adding
181    .sp
182    --enable-ebcdic    --enable-ebcdic
183    .sp
184  to the \fBconfigure\fR command.  to the \fBconfigure\fP command.
185    .P
186  .in 0  .in 0
187  Last updated: 09 December 2003  Last updated: 15 August 2005
188  .br  .br
189  Copyright (c) 1997-2003 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.

Legend:
Removed from v.73  
changed lines
  Added in v.83

  ViewVC Help
Powered by ViewVC 1.1.5