PCRE2  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 PCRE2 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 PCRE2 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 if you are using CMake instead of  configure
       to build PCRE2.

       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 "on/off" options whose
       names begin with --enable or --disable. Because of the way that config-
       ure  works, --enable and --disable always come in pairs, so the comple-
       mentary option always exists as well, but as it specifies the  default,
       it is not described.  Options that specify values have names that start
       with --with. At the end of a configure run, a summary of the configura-
       tion is output.


       By  default, a library called libpcre2-8 is built, containing functions
       that take string arguments contained in arrays  of  bytes,  interpreted
       either  as single-byte characters, or UTF-8 strings. You can also build
       two other libraries, called libpcre2-16 and libpcre2-32, which  process
       strings  that  are contained in arrays of 16-bit and 32-bit code units,
       respectively. These can be interpreted either as single-unit characters
       or  UTF-16/UTF-32 strings. To build these additional libraries, add one
       or both of the following to the configure command:


       The  Autotools PCRE2 building process uses libtool to build both shared
       and static libraries by default. You can suppress an  unwanted  library
       by adding one of


       to the configure command.


       By  default,  PCRE2 is built with support for Unicode and UTF character
       strings.  To build it without Unicode support, add


       to the configure command. This setting applies to all three  libraries.
       It  is  not  possible  to  build  one library with Unicode support, and
       another without, in the same configuration.

       Of itself, Unicode support does not make PCRE2 treat strings as  UTF-8,
       UTF-16 or UTF-32. To do that, applications that use the library can set
       the PCRE2_UTF option when they call pcre2_compile() to compile  a  pat-
       tern.   Alternatively,  patterns  may be started with (*UTF) unless the
       application has locked this out by setting PCRE2_NEVER_UTF.

       UTF support allows the libraries to process character code points up to
       0x10ffff  in  the  strings that they handle. Unicode support also gives
       access to the Unicode properties of characters, using  pattern  escapes
       such as \P, \p, and \X. Only the general category properties such as Lu
       and Nd are supported. Details are given in the pcre2pattern  documenta-

       Pattern escapes such as \d and \w do not by default make use of Unicode
       properties. The application can request that they  do  by  setting  the
       PCRE2_UCP  option.  Unless  the  application has set PCRE2_NEVER_UCP, a
       pattern may also request this by starting with (*UCP).


       The \C escape sequence, which matches a single code unit, even in a UTF
       mode,  can  cause unpredictable behaviour because it may leave the cur-
       rent matching point in the middle of a multi-code-unit  character.  The
       application  can  lock  it  out  by setting the PCRE2_NEVER_BACKSLASH_C
       option when calling pcre2_compile(). There is also a build-time option


       (note the upper case C) which locks out the use of \C entirely.


       Just-in-time (JIT) compiler support is included in the build by  speci-
       may also want to add


       which enables the use of an execmem allocator in JIT that is compatible
       with  SELinux.  This  has  no  effect  if  JIT  is not enabled. See the
       pcre2jit documentation for a discussion of JIT usage. When JIT  support
       is enabled, pcre2grep automatically makes use of it, unless you add


       to the "configure" command.


       By  default, PCRE2 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 PCRE2 to use carriage return (CR) instead, by


       to the configure  command.  There  is  also  an  --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 (CR immediately followed by LF). If you
       want this, add


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


       which  causes  PCRE2 to recognize any of the three sequences CR, LF, or
       CRLF as indicating a line ending. A fifth option, specified by


       causes PCRE2 to recognize any Unicode  newline  sequence.  The  Unicode
       newline sequences are the three just mentioned, plus the single charac-
       ters VT (vertical tab, U+000B), FF (form feed, U+000C), NEL (next line,
       U+0085),  LS  (line  separator,  U+2028),  and PS (paragraph separator,
       U+2029). The final option is


       which causes NUL (binary zero) to be set  as  the  default  line-ending

       Whatever default line ending convention is selected when PCRE2 is built
       can be overridden by applications that use the library. At  build  time
       it is recommended to use the standard for your operating system.


       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 64 thousand code units. This is suffi-
       cient to handle all but the most gigantic patterns. Nevertheless,  some
       people do want to process truly enormous patterns, so it is possible to
       compile PCRE2 to use three-byte or four-byte offsets by adding  a  set-
       ting 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 PCRE2 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.


       The pcre2_match() function increments a counter each time it goes round
       its  main  loop. Putting a limit on this counter controls the amount of
       computing resource used by a single call to  pcre2_match().  The  limit
       can be changed at run time, as described in the pcre2api documentation.
       The default is 10 million, but this can be changed by adding a  setting
       such as


       to   the   configure   command.   This  setting  also  applies  to  the
       pcre2_dfa_match() matching function, and to JIT  matching  (though  the
       counting is done differently).

       The  pcre2_match() function starts out using a 20KiB vector on the sys-
       tem stack to record backtracking points. The more  nested  backtracking
       points there are (that is, the deeper the search tree), the more memory
       is needed. If the initial vector is not large enough,  heap  memory  is
       used,  up to a certain limit, which is specified in kibibytes (units of
       1024 bytes). The limit can be changed at run time, as described in  the
       pcre2api  documentation.  The default limit (in effect unlimited) is 20
       million. You can change this by a setting such as


       which limits the amount of heap to 500 KiB. This limit applies only  to
       interpretive matching in pcre2_match() and pcre2_dfa_match(), which may
       also use the heap for internal workspace  when  processing  complicated
       patterns.  This limit does not apply when JIT (which has its own memory
       arrangements) is used.

       This limit was more useful in versions  before  10.30,  where  function
       recursion was used for backtracking.

       As well as applying to pcre2_match(), the depth limit also controls the
       depth of recursive function calls in pcre2_dfa_match(). These are  used
       for  lookaround  assertions,  atomic  groups, and recursion within pat-
       terns.  The limit does not apply to JIT matching.


       PCRE2 uses fixed tables for processing characters whose code points are
       less than 256. By default, PCRE2 is built with a set of tables that are
       distributed in the file src/pcre2_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".


       PCRE2  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. PCRE2 can, however, be
       compiled to run in an 8-bit EBCDIC environment by adding

         --enable-ebcdic --disable-unicode

       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).

       It is not possible to support both EBCDIC and UTF-8 codes in  the  same
       version  of  the  library. Consequently, --enable-unicode and --enable-
       ebcdic are mutually exclusive.

       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 char-
       acter (which, in Unicode, is 0x85).

       The options that select newline behaviour, such as --enable-newline-is-


       By default, pcre2grep 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 rel-
       evant  libraries  are installed on your system. Configuration will fail
       if they are not.


       pcre2grep 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 default starting size of the buffer is 20KiB. 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 notional buffer size. If a longer line is encoun-
       tered, pcre2grep automatically expands the buffer, up  to  a  specified
       maximum  size, whose default is 1MiB or the starting size, whichever is
       the larger. You can change the default parameter values by adding,  for


       to  the  configure  command. The caller of pcre2grep can override these
       values by using --buffer-size  and  --max-buffer-size  on  the  command


       If you add one of


       to  the  configure  command,  pcre2test  is linked with the libreadline
       orlibedit library, respectively, 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 pcre2test linked in this way, there may be
       licensing issues. These can be avoided by linking instead with libedit,
       which has a BSD licence.

       Setting  --enable-pcre2test-libreadline causes the -lreadline option to
       be added to the pcre2test build. In many operating environments with  a
       sytem-installed  readline  library this is sufficient. However, in some
       environments (e.g. if an unmodified distribution version of readline is
       immediately before the configure command.


       If you add


       to  the configure command, additional debugging code is included in the
       build. This feature is intended for use by the PCRE2 maintainers.


       If you add


       to the configure command, PCRE2 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  PCRE2


       If  your  C  compiler is gcc, you can build a version of PCRE2 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 PCRE2 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 PCRE2, 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 PCRE2 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
         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-


       The C99 standard defines formatting modifiers z and t  for  size_t  and
       ptrdiff_t  values, respectively. By default, PCRE2 uses these modifiers
       in environments other than Microsoft  Visual  Studio  when  __STDC_VER-
       SION__  is  defined  and  has  a value greater than or equal to 199901L
       (indicating C99).  However, there is  at  least  one  environment  that
       claims to be C99 but does not support these modifiers. If


       is specified, no use is made of the z or t modifiers. Instead or %td or
       %zu, %lu is used, with a cast for size_t values.


       There is a special option for use by people who  want  to  run  fuzzing
       tests on PCRE2:


       At present this applies only to the 8-bit library. If set, it causes an
       extra library  called  libpcre2-fuzzsupport.a  to  be  built,  but  not
       installed.  This contains a single function called LLVMFuzzerTestOneIn-
       put() whose arguments are a pointer to a string and the length  of  the
       string.  When  called,  this  function tries to compile the string as a
       pattern, and if that succeeds, to match it.  This is done both with  no
       options  and  with some random options bits that are generated from the

       Setting --enable-fuzz-support also causes  a  binary  called  pcre2fuz-
       zcheck  to be created. This is normally run under valgrind or used when
       PCRE2 is compiled with address sanitizing enabled. It calls the fuzzing
       function  and  outputs  information  about  what it is doing. The input
       strings are specified by arguments: if an argument starts with "="  the
       rest  of it is a literal input string. Otherwise, it is assumed to be a
       file name, and the contents of the file are the test string.


       In versions of PCRE2 prior to 10.30, there were two  ways  of  handling
       backtracking  in the pcre2_match() function. The default was to use the
       system stack, but if

       Philip Hazel
       University Computing Service
       Cambridge, England.


       Last updated: 03 March 2019
       Copyright (c) 1997-2019 University of Cambridge.

PCRE2 10.33                      03 March 2019                   PCRE2BUILD(3)
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