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pcrebuild(3)                                                      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 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.


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 dese-
       lected 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 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  complemen-
       tary  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 libpcre16, in which strings are con-
       tained in vectors of 16-bit data units and interpreted either  as  sin-
       gle-unit characters 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 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

         --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 with-
       out  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 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 charac-
       ters. 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 documentation 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. What-
       ever 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 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 func-
       tion uses space on the stack, because this is faster  than  using  mal-
       loc()  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 alter-
       nation 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

         --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 backtrack-
       ing  by  making recursive calls to an internal function called match().
       In environments where the size of the stack is limited,  this  can  se-
       verely  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 docu-
       mentation.) 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  manage-
       ment  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().


LIMITING PCRE RESOURCE USAGE


       Internally, PCRE has a function called match(), which it calls  repeat-
       edly   (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 documen-
       tation. 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 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_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,  how-
       ever, be compiled to run in an EBCDIC environment by adding

         --enable-ebcdic

       to the configure command. This setting implies --enable-rebuild-charta-
       bles. 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

         --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 correspond to the Unicode NEL char-
       acter (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 rel-
       evant 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  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 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

         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 incompatible 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 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  cover-
       age 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 docu-
       mentation.


SEE ALSO


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



PCRE 8.33                         12 May 2013                     pcrebuild(3)

pcre 8.33 - Generated Tue May 28 08:50:35 CDT 2013
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