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pcre2build(3)              Library Functions Manual              pcre2build(3)


NAME

       PCRE2 - Perl-compatible regular expressions (revised API)


BUILDING PCRE2

       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. The files in the vms directory support building under OpenVMS.
       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.


PCRE2 BUILD-TIME OPTIONS

       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.


BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES

       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:

         --enable-pcre2-16
         --enable-pcre2-32

       If you do not want the 8-bit library, add

         --disable-pcre2-8

       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.


BUILDING SHARED AND STATIC 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

         --disable-shared
         --disable-static

       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 linking.


UNICODE AND UTF SUPPORT

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

         --disable-unicode

       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 (*UCP).


DISABLING THE USE OF \C

       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

         --enable-never-backslash-C

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


JUST-IN-TIME COMPILER SUPPORT

       Just-in-time (JIT) 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 building error
       occurs.  If in doubt, use

         --enable-jit=auto

       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

         --enable-jit-sealloc

       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

         --disable-pcre2grep-jit

       to the configure command.


NEWLINE RECOGNITION

       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

         --enable-newline-is-cr

       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

         --enable-newline-is-crlf

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

         --enable-newline-is-anycrlf

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

         --enable-newline-is-any

       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

         --enable-newline-is-nul

       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

       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

         --enable-bsr-anycrlf

       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.


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
       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

         --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 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.


LIMITING PCRE2 RESOURCE USAGE

       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

         --with-match-limit=500000

       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 as

         --with-heap-limit=500

       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.

       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,

         --with-match-limit-depth=10000

       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.


LIMITING VARIABLE-LENGTH LOOKBEHIND ASSERTIONS

       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

         --with-max-varlookbehind=100

       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.


CREATING CHARACTER TABLES AT BUILD TIME

       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

         --enable-rebuild-chartables

       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 example:

         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 behaviour.


USING EBCDIC CODE

       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 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

         --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
       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.


PCRE2GREP SUPPORT FOR EXTERNAL SCRIPTS

       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.


PCRE2GREP OPTIONS FOR COMPRESSED FILE SUPPORT

       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

         --enable-pcre2grep-libz
         --enable-pcre2grep-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.


PCRE2GREP BUFFER SIZE

       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,

         --with-pcre2grep-bufsize=51200
         --with-pcre2grep-max-bufsize=2097152

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


PCRE2TEST OPTION FOR LIBREADLINE SUPPORT

       If you add one of

         --enable-pcre2test-libreadline
         --enable-pcre2test-libedit

       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
       system-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 like

         LIBS="-ncurses"

       immediately before the configure command.


INCLUDING DEBUGGING CODE

       If you add

         --enable-debug

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


DEBUGGING WITH VALGRIND SUPPORT

       If you add

         --enable-valgrind

       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.


CODE COVERAGE REPORTING

       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

         --enable-coverage

       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

         CCACHE_DISABLE=1

       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.


DISABLING THE Z AND T FORMATTING MODIFIERS

       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

         --disable-percent-zt

       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.


SUPPORT FOR FUZZERS

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

         --enable-fuzz-support

       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.


OBSOLETE OPTION

       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

         --disable-stack-for-recursion

       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

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


AUTHOR

       Philip Hazel
       Retired from University Computing Service
       Cambridge, England.


REVISION

       Last updated: 15 April 2024
       Copyright (c) 1997-2024 University of Cambridge.

PCRE2 10.44                      15 April 2024                   pcre2build(3)

pcre2 10.44 - Generated Mon Jun 17 07:27:10 CDT 2024
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