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+++ b/libraries/spcre/libpcre/pcre/doc/pcrebuild.3	Wed Jun 23 15:52:26 2010 +0100
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+.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.
+.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: 13 April 2008
+Copyright (c) 1997-2008 University of Cambridge.
+.fi