214 lines
8.1 KiB
Groff
214 lines
8.1 KiB
Groff
.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. They are all selected, or deselected, by providing
|
|
options to the \fBconfigure\fP script that is run before the \fBmake\fP
|
|
command. 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 describe certain 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 90K of tables to the PCRE
|
|
library, approximately doubling its size. 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. 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 "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.
|
|
.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.
|
|
.
|
|
.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. Separate functions are provided 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 the standard \fBmalloc()\fP and
|
|
\fBfree()\fP functions. 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 "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). PCRE can, however, be
|
|
compiled to run in an EBCDIC environment by adding
|
|
.sp
|
|
--enable-ebcdic
|
|
.sp
|
|
to the \fBconfigure\fP command.
|
|
.P
|
|
.in 0
|
|
Last updated: 06 June 2006
|
|
.br
|
|
Copyright (c) 1997-2006 University of Cambridge.
|