PCREBUILD(3)              (12 May 2013)              PCREBUILD(3)

          PCRE - Perl-compatible regular expressions


          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-

          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.


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          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


          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


          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

          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.

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          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 --

          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 functions.

          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.


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


          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 adding


          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 by


          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

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          for your operating system.


          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 as


          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-

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          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,


          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 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 pcre_dfa_exec().


          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.

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          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 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


          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

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          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


          If you add


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          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

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          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

          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

            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.


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


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


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

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