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 .P

   286 Setting this option causes the \fB-lreadline\fP option to be added to the

   287 \fBpcretest\fP build. In many operating environments with a sytem-installed

   288 \fBlibreadline\fP this is sufficient. However, in some environments (e.g.

   289 if an unmodified distribution version of readline is in use), some extra

   290 configuration may be necessary. The INSTALL file for \fBlibreadline\fP says

   291 this:

   292 .sp

   293   "Readline uses the termcap functions, but does not link with the

   294   termcap or curses library itself, allowing applications which link

   295   with readline the to choose an appropriate library."

   296 .sp

   297 If your environment has not been set up so that an appropriate library is

   298 automatically included, you may need to add something like

   299 .sp

   300   LIBS="-ncurses"

   301 .sp

   302 immediately before the \fBconfigure\fP command.

   303 .

   304 .

   305 .SH "SEE ALSO"

   306 .rs

   307 .sp

   308 \fBpcreapi\fP(3), \fBpcre_config\fP(3).

   309 .

   310 .

   311 .SH AUTHOR

   312 .rs

   313 .sp

   314 .nf

   315 Philip Hazel

   316 University Computing Service

   317 Cambridge CB2 3QH, England.

   318 .fi

   319 .

   320 .

   321 .SH REVISION

   322 .rs

   323 .sp

   324 .nf

   325 Last updated: 13 April 2008

   326 Copyright (c) 1997-2008 University of Cambridge.

   327 .fi