.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 Unicode 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.

 .P

 If you set --enable-utf8 when compiling in an EBCDIC environment, PCRE expects

 its input to be either ASCII or UTF-8 (depending on the runtime option). It is

 not possible to support both EBCDIC and UTF-8 codes in the same version of the

 library. Consequently, --enable-utf8 and --enable-ebcdic are mutually

 exclusive.

 .

 .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 the linefeed (LF) character as indicating the end

 of a line. This is the normal newline character on Unix-like systems. You can

 compile PCRE to use 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). The

 --enable-ebcdic option is incompatible with --enable-utf8.

 .

 .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.

 .P

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

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

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

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

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

 this:

 .sp

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

   termcap or curses library itself, allowing applications which link

   with readline the to choose an appropriate library."

 .sp

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

 automatically included, you may need to add something like

 .sp

   LIBS="-ncurses"

 .sp

 immediately before the \fBconfigure\fP command.

 .

 .

 .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: 17 March 2009

 Copyright (c) 1997-2009 University of Cambridge.

 .fi