pcre2build(3) — Linux manual page


PCRE2BUILD(3)           Library Functions Manual           PCRE2BUILD(3)

NAME         top

       PCRE2 - Perl-compatible regular expressions (revised API)

BUILDING PCRE2         top

       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 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 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 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.  Options that
       specify values have names that start with --with. At the end of a
       configure run, a summary of the configuration 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


       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 POSIX wrapper is for the 8-bit library only, and that
       pcre2grep is an 8-bit program. Neither of these are built if you
       select only the 16-bit or 32-bit libraries.


       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. Setting --disable-shared ensures that
       PCRE2 libraries are built as static libraries. The binaries that
       are then created as part of the build process (for example,
       pcre2test and pcre2grep) are linked statically with one or more
       PCRE2 libraries, but may also be dynamically linked with other
       libraries such as libc. If you want these binaries to be fully
       statically linked, you can set LDFLAGS like this:

       LDFLAGS=--static ./configure --disable-shared

       Note the two hyphens in --static. Of course, this works only if
       static versions of all the relevant libraries are available for


       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 pattern.  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, script names, and some bi-
       directional properties are supported. Details are given in the
       pcre2pattern documentation.

       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


       The \C escape sequence, which matches a single code unit, even in
       a UTF mode, can cause unpredictable behaviour because it may
       leave the current 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


       This support is available only for certain hardware
       architectures. If this option is set for an unsupported
       architecture, a building error occurs.  If in doubt, use


       which enables JIT only if the current hardware is supported. You
       can check if JIT is enabled in the configuration summary that is
       output at the end of a configure run. If you are enabling JIT
       under SELinux you 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 adding


       to the configure command. There is also an --enable-newline-is-lf
       option, which explicitly specifies linefeed as the newline

       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 characters 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 character.

       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.

WHAT \R MATCHES         top

       By default, the sequence \R in a pattern matches any Unicode
       newline sequence, independently of what 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 PCRE2 is built can be overridden by
       applications that use the library.


       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 64
       thousand code units. 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
       PCRE2 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 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 uses heap memory to record
       backtracking points. The more nested backtracking points there
       are (that is, the deeper the search tree), the more memory is
       needed. There is an upper limit, specified in kibibytes (units of
       1024 bytes). This 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


       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

       You can also explicitly limit the depth of nested backtracking in
       the pcre2_match() interpreter. This limit defaults to the value
       that is set for --with-match-limit. You can set a lower default
       limit by adding, for example,


       to the configure command. This value can be overridden at run
       time. This depth limit indirectly limits the amount of heap
       memory that is used, but because the size of each backtracking
       "frame" depends on the number of capturing parentheses in a
       pattern, the amount of heap that is used before the limit is
       reached varies from pattern to pattern. 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 patterns.  The limit does not
       apply to JIT matching.


       Lookbehind assertions in which one or more branches can match a
       variable number of characters are supported only if there is a
       maximum matching length for each top-level branch. There is a
       limit to this maximum that defaults to 255 characters. You can
       alter this default by a setting such as


       The limit can be changed at runtime by calling
       pcre2_set_max_varlookbehind(). Lookbehind assertions in which
       every branch matches a fixed number of characters (not
       necessarily all the same) are not constrained by this limit.


       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 pcre2_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 pcre2_dftables needs to be run on the local host and
       therefore not compiled with the cross compiler.

       If you need to create alternative tables when cross compiling,
       you will have to do so "by hand". There may also be other reasons
       for creating tables manually.  To cause pcre2_dftables to be
       built on the local host, run a normal compiling command, and then
       run the program with the output file as its argument, for

         cc src/pcre2_dftables.c -o pcre2_dftables
         ./pcre2_dftables src/pcre2_chartables.c

       This builds the tables in the default locale of the local host.
       If you want to specify a locale, you must use the -L option:

         LC_ALL=fr_FR ./pcre2_dftables -L src/pcre2_chartables.c

       You can also specify -b (with or without -L). This causes the
       tables to be written in binary instead of as source code. A set
       of binary tables can be loaded into memory by an application and
       passed to pcre2_compile() in the same way as tables created by
       calling pcre2_maketables(). The tables are just a string of
       bytes, independent of hardware characteristics such as
       endianness. This means they can be bundled with an application
       that runs in different environments, to ensure consistent


       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-
       chartables. You should only use it if you know that you are in an
       EBCDIC environment (for example, an IBM mainframe operating

       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 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 pcre2grep supports the use of callouts with string
       arguments within the patterns it is matching. There are two
       kinds: one that generates output using local code, and another
       that calls an external program or script.  If --disable-
       pcre2grep-callout-fork is added to the configure command, only
       the first kind of callout is supported; if --disable-pcre2grep-
       callout is used, all callouts are completely ignored. For more
       details of pcre2grep callouts, see the pcre2grep documentation.


       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 relevant 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 encountered, 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 example,


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


       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 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


       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


       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 itself.


       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


       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

       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.


       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 old versions of Microsoft
       Visual Studio when __STDC_VERSION__ is defined and has a value
       greater than or equal to 199901L (indicating support for 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 of
       %td or %zu, a suitable format is used depending in the size of
       long for the platform.


       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
       LLVMFuzzerTestOneInput() 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 string.

       Setting --enable-fuzz-support also causes a binary called
       pcre2fuzzcheck 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


       was set, memory on the heap was used. From release 10.30 onwards
       this has changed (the stack is no longer used) and this option
       now does nothing except give a warning.

SEE ALSO         top

       pcre2api(3), pcre2-config(3).

AUTHOR         top

       Philip Hazel
       Retired from University Computing Service
       Cambridge, England.

REVISION         top

       Last updated: 24 November 2023
       Copyright (c) 1997-2023 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 ⟨http://www.pcre.org/⟩.  If you have a bug report for this
       manual page, see
       ⟨http://bugs.exim.org/enter_bug.cgi?product=PCRE⟩.  This page was
       obtained from the tarball fetched from
       ⟨https://github.com/PhilipHazel/pcre2.git⟩ on 2023-12-22.  If you
       discover any rendering problems in this HTML version 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
       manual page), send a mail to man-pages@man7.org

PCRE2 10.43                    24 November                 PCRE2BUILD(3)

Pages that refer to this page: pcre2api(3)