pcre2build (3) - Linux Manuals
pcre2build: Perl-compatible regular expressions (revised API)
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. 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
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 command:
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
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 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).
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 specifying
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
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 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 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.
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 starts out using a 20KiB vector on the system
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.
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.
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
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
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:
If your environment has not been set up so that an appropriate library is
automatically included, you may need to add something like
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 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 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:
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".
This zeroes the coverage counters, but does nothing else.
This captures baseline coverage information.
This creates the coverage report.
This removes the generated coverage report without cleaning the coverage data
itself.
This removes the captured coverage data without removing the coverage files
created at compile time (*.gcno).
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 Microsoft Visual Studio when __STDC_VERSION__ 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 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.
pcre2api(3), pcre2-config(3).
BUILDING 8-BIT, 16-BIT AND 32-BIT LIBRARIES
BUILDING SHARED AND STATIC LIBRARIES
UNICODE AND UTF SUPPORT
DISABLING THE USE OF \C
JUST-IN-TIME COMPILER SUPPORT
NEWLINE RECOGNITION
WHAT \R MATCHES
HANDLING VERY LARGE PATTERNS
LIMITING PCRE2 RESOURCE USAGE
CREATING CHARACTER TABLES AT BUILD TIME
USING EBCDIC CODE
PCRE2GREP SUPPORT FOR EXTERNAL SCRIPTS
PCRE2GREP OPTIONS FOR COMPRESSED FILE SUPPORT
PCRE2GREP BUFFER SIZE
PCRE2TEST OPTION FOR LIBREADLINE SUPPORT
INCLUDING DEBUGGING CODE
DEBUGGING WITH VALGRIND SUPPORT
CODE COVERAGE REPORTING
DISABLING THE Z AND T FORMATTING MODIFIERS
SUPPORT FOR FUZZERS
OBSOLETE OPTION
AUTHOR
Philip Hazel
University Computing Service
Cambridge, England.
REVISION
Last updated: 03 March 2019
Copyright (c) 1997-2019 University of Cambridge.
SEE ALSO