pcrebuild(3)
PCREBUILD(3) C LIBRARY FUNCTIONS PCREBUILD(3)
NAME
PCRE - Perl-compatible regular expressions
BUILDING PCRE
PCRE is distributed with a configure script that can be used
to build the library in Unix-like environments using the
applications known as Autotools. Also in the distribution
are files to support building using CMake instead of config-
ure. The text file README contains general information about
building with Autotools (some of which is repeated below),
and also has some comments about building on various operat-
ing systems. There is a lot more information about building
PCRE without using Autotools (including information about
using CMake and building "by hand") in the text file called
NON-AUTOTOOLS-BUILD. You should consult this file as well
as the README file if you are building in a non-Unix-like
environment.
PCRE BUILD-TIME OPTIONS
The rest of this document describes the optional features of
PCRE that can be selected when the library is compiled. It
assumes use of the configure script, where the optional
features are selected or deselected by providing options to
configure before running the make command. However, the same
options can be selected in both Unix-like and non-Unix-like
environments using the GUI facility of cmake-gui if you are
using CMake instead of configure to build PCRE. If you are
not using Autotools or CMake, option selection can be done
by editing the config.h file, or by passing parameter set-
tings to the compiler, as described in NON-AUTOTOOLS-BUILD.
The complete list of options for configure (which includes
the standard ones such as the selection of the installation
directory) can be obtained by running
./configure --help
The following sections include descriptions of options whose
names begin with --enable or --disable. These settings
specify changes to the defaults for the configure command.
Because of the way that configure 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.
BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES
By default, a library called libpcre is built, containing
functions that take string arguments contained in vectors of
bytes, either as single-byte characters, or interpreted as
UTF-8 strings. You can also build a separate library, called
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libpcre16, in which strings are contained in vectors of 16-
bit data units and interpreted either as single-unit charac-
ters or UTF-16 strings, by adding
--enable-pcre16
to the configure command. You can also build yet another
separate library, called libpcre32, in which strings are
contained in vectors of 32-bit data units and interpreted
either as single-unit characters or UTF-32 strings, by
adding
--enable-pcre32
to the configure command. If you do not want the 8-bit
library, add
--disable-pcre8
as well. At least one of the three libraries must be built.
Note that the C++ and POSIX wrappers are for the 8-bit
library only, and that pcregrep is an 8-bit program. None of
these are built if you select only the 16-bit or 32-bit
libraries.
BUILDING SHARED AND STATIC LIBRARIES
The Autotools PCRE building process uses libtool to build
both shared and static libraries by default. You can
suppress one of these by adding one of
--disable-shared
--disable-static
to the configure command, as required.
C++ SUPPORT
By default, if the 8-bit library is being built, the config-
ure script will search for a C++ compiler and C++ header
files. If it finds them, it automatically builds the C++
wrapper library (which supports only 8-bit strings). You can
disable this by adding
--disable-cpp
to the configure command.
UTF-8, UTF-16 AND UTF-32 SUPPORT
To build PCRE with support for UTF Unicode character
strings, add
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--enable-utf
to the configure command. This setting applies to all three
libraries, adding support for UTF-8 to the 8-bit library,
support for UTF-16 to the 16-bit library, and support for
UTF-32 to the to the 32-bit library. There are no separate
options for enabling UTF-8, UTF-16 and UTF-32 independently
because that would allow ridiculous settings such as
requesting UTF-16 support while building only the 8-bit
library. It is not possible to build one library with UTF
support and another without in the same configuration. (For
backwards compatibility, --enable-utf8 is a synonym of --
enable-utf.) Of itself, this setting does not make PCRE
treat strings as UTF-8, UTF-16 or UTF-32. As well as compil-
ing PCRE with this option, you also have have to set the
PCRE_UTF8, PCRE_UTF16 or PCRE_UTF32 option (as appropriate)
when you call one of the pattern compiling functions. If
you set --enable-utf when compiling in an EBCDIC environ-
ment, PCRE expects its input to be either ASCII or UTF-8
(depending on the run-time option). It is not possible to
support both EBCDIC and UTF-8 codes in the same version of
the library. Consequently, --enable-utf and --enable-ebcdic
are mutually exclusive.
UNICODE CHARACTER PROPERTY SUPPORT
UTF support allows the libraries to process character
codepoints up to 0x10ffff in the strings that they handle.
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 \P, \p, and \X, which
refer to Unicode character properties, you must add
--enable-unicode-properties
to the configure command. This implies UTF support, even if
you have not explicitly requested it. Including Unicode
property support adds around 30K of tables to the PCRE
library. Only the general category properties such as Lu and
Nd are supported. Details are given in the pcrepattern docu-
mentation.
JUST-IN-TIME COMPILER SUPPORT
Just-in-time compiler support is included in the build by
specifying
--enable-jit
This support is available only for certain hardware archi-
tectures. If this option is set for an unsupported architec-
ture, a compile time error occurs. See the pcrejit
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documentation for a discussion of JIT usage. When JIT sup-
port is enabled, pcregrep automatically makes use of it,
unless you add
--disable-pcregrep-jit
to the "configure" command.
CODE VALUE OF NEWLINE
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
--enable-newline-is-cr
to the configure command. There is also a --enable-newline-
is-lf option, which explicitly specifies linefeed as the
newline character.
Alternatively, you can specify that line endings are to be
indicated by the two character sequence CRLF. If you want
this, add
--enable-newline-is-crlf
to the configure command. There is a fourth option, speci-
fied by
--enable-newline-is-anycrlf
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
--enable-newline-is-any
causes PCRE to recognize any Unicode newline sequence.
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.
WHAT \R MATCHES
By default, the sequence \R in a pattern matches any Unicode
newline sequence, whatever has been selected as the line
ending sequence. If you specify
--enable-bsr-anycrlf
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the default is changed so that \R matches only CR, LF, or
CRLF. Whatever is selected when PCRE is built can be over-
ridden when the library functions are called.
POSIX MALLOC USAGE
When the 8-bit library is called through the POSIX interface
(see the pcreposix documentation), additional working
storage is required for holding the pointers to capturing
substrings, because PCRE requires three integers per sub-
string, 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 malloc() 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
--with-posix-malloc-threshold=20
to the configure command.
HANDLING VERY LARGE PATTERNS
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, in
the 8-bit and 16-bit libraries, two-byte values are used for
these offsets, leading to a maximum size for a compiled pat-
tern of around 64K. This is sufficient to handle all but the
most gigantic patterns. Nevertheless, some people do want
to process truly enormous patterns, so it is possible to
compile PCRE to use three-byte or four-byte offsets by
adding a setting such as
--with-link-size=3
to the configure command. The value given must be 2, 3, or
4. For the 16-bit library, a value of 3 is rounded up to 4.
In these libraries, using longer offsets slows down the
operation of PCRE because it has to load additional data
when handling them. For the 32-bit library the value is
always 4 and cannot be overridden; the value of --with-
link-size is ignored.
AVOIDING EXCESSIVE STACK USAGE
When matching with the pcre_exec() function, PCRE implements
backtracking by making recursive calls to an internal func-
tion called match(). 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
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maximum stack size. There is a discussion in the pcrestack
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
--disable-stack-for-recursion
to the configure command. With this configuration, PCRE will
use the pcre_stack_malloc and pcre_stack_free variables to
call memory management functions. By default these point to
malloc() and free(), but you can replace the pointers so
that your own functions are used instead. Separate func-
tions are provided rather than using pcre_malloc and
pcre_free 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 malloc() and free(). PCRE runs noticeably more slowly
when built in this way. This option affects only the
pcre_exec() function; it is not relevant for
pcre_dfa_exec().
LIMITING PCRE RESOURCE USAGE
Internally, PCRE has a function called match(), which it
calls repeatedly (sometimes recursively) when matching a
pattern with the pcre_exec() 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 pcre_exec(). The limit
can be changed at run time, as described in the pcreapi
documentation. The default is 10 million, but this can be
changed by adding a setting such as
--with-match-limit=500000
to the configure command. This setting has no effect on the
pcre_dfa_exec() matching function. In some environments it
is desirable to limit the depth of recursive calls of
match() 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 con-
straints. However, you can set a lower limit by adding, for
example,
--with-match-limit-recursion=10000
to the configure command. This value can also be overridden
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at run time.
CREATING CHARACTER TABLES AT BUILD TIME
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
pcre_chartables.c.dist. These tables are for ASCII codes
only. If you add
--enable-rebuild-chartables
to the configure command, the distributed tables are no
longer used. Instead, a program called dftables is compiled
and run. This outputs the source for new set of tables,
created in the default locale of your C run-time system.
(This method of replacing the tables does not work if you
are cross compiling, because dftables is run on the local
host. If you need to create alternative tables when cross
compiling, you will have to do so "by hand".)
USING EBCDIC CODE
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
--enable-ebcdic
to the configure 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 main-
frame operating system). The --enable-ebcdic option is
incompatible with --enable-utf. The EBCDIC character that
corresponds to an ASCII LF is assumed to have the value 0x15
by default. However, in some EBCDIC environments, 0x25 is
used. In such an environment you should use
--enable-ebcdic-nl25
as well as, or instead of, --enable-ebcdic. The EBCDIC char-
acter for CR has the same value as in ASCII, namely, 0x0d.
Whichever of 0x15 and 0x25 is not chosen as LF is made to
correspond to the Unicode NEL character (which, in Unicode,
is 0x85). The options that select newline behaviour, such
as --enable-newline-is-cr, and equivalent run-time options,
refer to these character values in an EBCDIC environment.
PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
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By default, pcregrep reads all files as plain text. You can
build it so that it recognizes files whose names end in .gz
or .bz2, and reads them with libz or libbz2, respectively,
by adding one or both of
--enable-pcregrep-libz
--enable-pcregrep-libbz2
to the configure command. These options naturally require
that the relevant libraries are installed on your system.
Configuration will fail if they are not.
PCREGREP BUFFER SIZE
pcregrep uses an internal buffer to hold a "window" on the
file it is scanning, in order to be able to output "before"
and "after" lines when it finds a match. The size of the
buffer is controlled by a parameter whose default value is
20K. The buffer itself is three times this size, but because
of the way it is used for holding "before" lines, the long-
est line that is guaranteed to be processable is the parame-
ter size. You can change the default parameter value by
adding, for example,
--with-pcregrep-bufsize=50K
to the configure command. The caller of pcregrep can, how-
ever, override this value by specifying a run-time option.
PCRETEST OPTION FOR LIBREADLINE SUPPORT
If you add
--enable-pcretest-libreadline
to the configure command, pcretest is linked with the
libreadline library, and when its input is from a terminal,
it reads it using the readline() function. This provides
line-editing and history facilities. Note that libreadline
is GPL-licensed, so if you distribute a binary of pcretest
linked in this way, there may be licensing issues. Setting
this option causes the -lreadline option to be added to the
pcretest build. In many operating environments with a
sytem-installed libreadline this is sufficient. However, in
some environments (e.g. if an unmodified distribution ver-
sion of readline is in use), some extra configuration may be
necessary. The INSTALL file for libreadline says this:
"Readline uses the termcap functions, but does not link
with the
termcap or curses library itself, allowing applications
which link
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with readline the to choose an appropriate library."
If your environment has not been set up so that an appropri-
ate library is automatically included, you may need to add
something like
LIBS="-ncurses"
immediately before the configure command.
DEBUGGING WITH VALGRIND SUPPORT
By adding the
--enable-valgrind
option to to the configure command, PCRE will use valgrind
annotations to mark certain memory regions as unaddressable.
This allows it to detect invalid memory accesses, and is
mostly useful for debugging PCRE itself.
CODE COVERAGE REPORTING
If your C compiler is gcc, you can build a version of PCRE
that can generate a code coverage report for its test suite.
To enable this, you must install lcov version 1.6 or above.
Then specify
--enable-coverage
to the configure command and build PCRE in the usual way.
Note that using ccache (a caching C compiler) is incompati-
ble with code coverage reporting. If you have configured
ccache to run automatically on your system, you must set the
environment variable
CCACHE_DISABLE=1
before running make to build PCRE, so that ccache is not
used. When --enable-coverage is used, the following addi-
tion targets are added to the Makefile:
make coverage
This creates a fresh coverage report for the PCRE test
suite. It is equivalent to running "make coverage-reset",
"make coverage-baseline", "make check", and then "make
coverage-report".
make coverage-reset
This zeroes the coverage counters, but does nothing else.
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make coverage-baseline
This captures baseline coverage information.
make coverage-report
This creates the coverage report.
make coverage-clean-report
This removes the generated coverage report without cleaning
the coverage data itself.
make coverage-clean-data
This removes the captured coverage data without removing the
coverage files created at compile time (*.gcno).
make coverage-clean
This cleans all coverage data including the generated cover-
age report. For more information about code coverage, see
the gcov and lcov documentation.
SEE ALSO
pcreapi(3), pcre16, pcre32, pcre_config(3).
AUTHOR
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
REVISION
Last updated: 12 May 2013
Copyright (c) 1997-2013 University of Cambridge.
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