PCREBUILD(3)              Library Functions Manual              PCREBUILD(3)

NAME         top

       PCRE - Perl-compatible regular expressions

BUILDING PCRE         top

       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 configure. 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
       operating 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.


       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 settings 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.


       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 libpcre16, in which strings are
       contained in vectors of 16-bit data units and interpreted either as
       single-unit characters or UTF-16 strings, by adding


       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


       to the configure command. If you do not want the 8-bit library, add


       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.


       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


       to the configure command, as required.

C++ SUPPORT         top

       By default, if the 8-bit library is being built, the configure 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


       to the configure command.

UTF-8, UTF-16 AND UTF-32 SUPPORT         top

       To build PCRE with support for UTF Unicode character strings, add


       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 compiling 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

       If you set --enable-utf when compiling in an EBCDIC environment, 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.


       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


       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 documentation.


       Just-in-time compiler support is included in the build by specifying


       This support is available only for certain hardware architectures. If
       this option is set for an unsupported architecture, a compile time
       error occurs.  See the pcrejit documentation for a discussion of JIT
       usage. When JIT support is enabled, pcregrep automatically makes use
       of it, unless you add


       to the "configure" command.


       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


       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


       to the configure command. There is a fourth option, specified by


       which causes PCRE to recognize any of the three sequences CR, LF, or
       CRLF as indicating a line ending. Finally, a fifth option, specified


       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         top

       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


       the default is changed so that \R matches only CR, LF, or CRLF.
       Whatever is selected when PCRE is built can be overridden when the
       library functions are called.


       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 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
       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


       to the configure command.


       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 pattern 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


       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.


       When matching with the pcre_exec() function, PCRE implements
       backtracking by making recursive calls to an internal function 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 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


       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

       Separate functions 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


       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


       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 constraints. However, you can set
       a lower limit by adding, for example,


       to the configure command. This value can also be overridden at run


       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


       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".)


       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


       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 mainframe 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


       as well as, or instead of, --enable-ebcdic. The EBCDIC character 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.


       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


       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 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 longest line that is guaranteed to be processable
       is the parameter size. You can change the default parameter value by
       adding, for example,


       to the configure command. The caller of pcregrep can, however,
       override this value by specifying a run-time option.


       If you add


       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 version 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
         with readline the to choose an appropriate library."

       If your environment has not been set up so that an appropriate
       library is automatically included, you may need to add something like


       immediately before the configure command.


       By adding the


       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.


       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


       to the configure command and build PCRE in the usual way.

       Note that using ccache (a caching C compiler) is incompatible with
       code coverage reporting. If you have configured ccache to run
       automatically on your system, you must set the environment variable


       before running make to build PCRE, so that ccache is not used.

       When --enable-coverage is used, the following addition 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.

         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 coverage
       report. For more information about code coverage, see the gcov and
       lcov documentation.

SEE ALSO         top

       pcreapi(3), pcre16, pcre32, pcre_config(3).

AUTHOR         top

       Philip Hazel
       University Computing Service
       Cambridge CB2 3QH, England.

REVISION         top

       Last updated: 12 May 2013
       Copyright (c) 1997-2013 University of Cambridge.

COLOPHON         top

       This page is part of the PCRE (Perl Compatible Regular Expressions)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, see ⟨⟩.  This
       page was obtained from the tarball pcre-8.42.tar.gz fetched from
       ⟨⟩ on
       2018-04-30.  If you discover any rendering problems in this HTML ver‐
       sion of the page, or you believe there is a better or more up-to-date
       source for the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original man‐
       ual page), send a mail to

PCRE 8.33                        12 May 2013                    PCREBUILD(3)

Pages that refer to this page: pcreapi(3)