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PCREBUILD(3)                         Library Functions Manual                        PCREBUILD(3)



NAME
       PCRE - Perl-compatible regular expressions

PCRE BUILD-TIME OPTIONS

       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 com-
       mand. However, the same options can be selected in both Unix-like and non-Unix-like  envi-
       ronments  using  the GUI facility of cmake-gui if you are using CMake instead of configure
       to build PCRE.

       There is a lot more information about building PCRE  without  using  configure  (including
       information  about  using  CMake  or building "by hand") in the file called NON-AUTOTOOLS-
       BUILD, which is part of the PCRE distribution. You should consult this file as well as the
       README file if you are building in a non-Unix-like environment.

       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 argu-
       ments  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 char-
       acters or UTF-16 strings, by adding

         --enable-pcre16

       to the configure command. You can also build a  separate  library,  called  libpcre32,  in
       which strings are contained in vectors of 32-bit data units and interpreted either as sin-
       gle-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 PCRE building process uses libtool to build both shared and static Unix  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 configure script will search for a
       C++ compiler and C++ header files. If it finds them, it automatically builds the C++ wrap-
       per 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

         --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 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 compil-
       ing 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.

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 documentation.

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 architectures. If this option is set
       for an unsupported architecture, a compile time error occurs.  See the pcrejit  documenta-
       tion  for  a  discussion of JIT usage. When JIT support 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, specified 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

       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.

POSIX MALLOC USAGE

       When the 8-bit library is called through the POSIX interface (see the pcreposix documenta-
       tion), additional working storage is required for holding the pointers to  capturing  sub-
       strings,  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

         --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 maxi-
       mum 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 pat-
       terns, 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 recur-
       sive 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  maxi-
       mum  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  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 rele-
       vant 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  mil-
       lion, 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 func-
       tion.

       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 con-
       trols  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,

         --with-match-limit-recursion=10000

       to the configure command. This value can also be overridden 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_charta-
       bles.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, cre-
       ated 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 oper-
       ating 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 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  cor-
       respond 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

       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 longest
       line  that  is  guaranteed  to  be  processable  is the parameter 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,  however,  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 distrib-
       ute 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. How-
       ever, 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

         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 cover-
       age 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 incompatible with code coverage report-
       ing. 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 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  informa-
       tion 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: 30 October 2012
       Copyright (c) 1997-2012 University of Cambridge.



PCRE 8.32                                30 October 2012                             PCREBUILD(3)

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