1PCRE2BUILD(3) Library Functions Manual PCRE2BUILD(3)
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6 PCRE2 - Perl-compatible regular expressions (revised API)
7
9 PCRE2 is distributed with a configure script that can be used to build
11 the library in Unix-like environments using the applications known as
12 Autotools. Also in the distribution are files to support building using
13 CMake instead of configure. The text file README contains general
14 information about building with Autotools (some of which is repeated
15 below), and also has some comments about building on various operating
16 systems. There is a lot more information about building PCRE2 without
17 using Autotools (including information about using CMake and building
18 "by hand") in the text file called NON-AUTOTOOLS-BUILD. You should
19 consult this file as well as the README file if you are building in a
20 non-Unix-like environment.
21
23 The rest of this document describes the optional features of PCRE2 that
25 can be selected when the library is compiled. It assumes use of the
26 configure script, where the optional features are selected or dese‐
27 lected by providing options to configure before running the make com‐
28 mand. However, the same options can be selected in both Unix-like and
29 non-Unix-like environments if you are using CMake instead of configure
30 to build PCRE2.
31 If you are not using Autotools or CMake, option selection can be done
33 by editing the config.h file, or by passing parameter settings to the
34 compiler, as described in NON-AUTOTOOLS-BUILD.
35 The complete list of options for configure (which includes the standard
37 ones such as the selection of the installation directory) can be
38 obtained by running
39 ./configure --help
41 The following sections include descriptions of "on/off" options whose
43 names begin with --enable or --disable. Because of the way that config‐
44 ure works, --enable and --disable always come in pairs, so the comple‐
45 mentary option always exists as well, but as it specifies the default,
46 it is not described. Options that specify values have names that start
47 with --with. At the end of a configure run, a summary of the configura‐
48 tion is output.
49
51 By default, a library called libpcre2-8 is built, containing functions
53 that take string arguments contained in arrays of bytes, interpreted
54 either as single-byte characters, or UTF-8 strings. You can also build
55 two other libraries, called libpcre2-16 and libpcre2-32, which process
56 strings that are contained in arrays of 16-bit and 32-bit code units,
57 respectively. These can be interpreted either as single-unit characters
58 or UTF-16/UTF-32 strings. To build these additional libraries, add one
59 or both of the following to the configure command:
60 --enable-pcre2-16
62 --enable-pcre2-32
63 If you do not want the 8-bit library, add
65 --disable-pcre2-8
67 as well. At least one of the three libraries must be built. Note that
69 the POSIX wrapper is for the 8-bit library only, and that pcre2grep is
70 an 8-bit program. Neither of these are built if you select only the
71 16-bit or 32-bit libraries.
72
74 The Autotools PCRE2 building process uses libtool to build both shared
76 and static libraries by default. You can suppress an unwanted library
77 by adding one of
78 --disable-shared
80 --disable-static
81 to the configure command.
83
85 By default, PCRE2 is built with support for Unicode and UTF character
87 strings. To build it without Unicode support, add
88 --disable-unicode
90 to the configure command. This setting applies to all three libraries.
92 It is not possible to build one library with Unicode support, and
93 another without, in the same configuration.
94 Of itself, Unicode support does not make PCRE2 treat strings as UTF-8,
96 UTF-16 or UTF-32. To do that, applications that use the library can set
97 the PCRE2_UTF option when they call pcre2_compile() to compile a pat‐
98 tern. Alternatively, patterns may be started with (*UTF) unless the
99 application has locked this out by setting PCRE2_NEVER_UTF.
100 UTF support allows the libraries to process character code points up to
102 0x10ffff in the strings that they handle. Unicode support also gives
103 access to the Unicode properties of characters, using pattern escapes
104 such as \P, \p, and \X. Only the general category properties such as Lu
105 and Nd are supported. Details are given in the pcre2pattern documenta‐
106 tion.
107 Pattern escapes such as \d and \w do not by default make use of Unicode
109 properties. The application can request that they do by setting the
110 PCRE2_UCP option. Unless the application has set PCRE2_NEVER_UCP, a
111 pattern may also request this by starting with (*UCP).
112
114 The \C escape sequence, which matches a single code unit, even in a UTF
116 mode, can cause unpredictable behaviour because it may leave the cur‐
117 rent matching point in the middle of a multi-code-unit character. The
118 application can lock it out by setting the PCRE2_NEVER_BACKSLASH_C
119 option when calling pcre2_compile(). There is also a build-time option
120 --enable-never-backslash-C
122 (note the upper case C) which locks out the use of \C entirely.
124
126 Just-in-time (JIT) compiler support is included in the build by speci‐
128 fying
129 --enable-jit
131 This support is available only for certain hardware architectures. If
133 this option is set for an unsupported architecture, a building error
134 occurs. If in doubt, use
135 --enable-jit=auto
137 which enables JIT only if the current hardware is supported. You can
139 check if JIT is enabled in the configuration summary that is output at
140 the end of a configure run. If you are enabling JIT under SELinux you
141 may also want to add
142 --enable-jit-sealloc
144 which enables the use of an execmem allocator in JIT that is compatible
146 with SELinux. This has no effect if JIT is not enabled. See the
147 pcre2jit documentation for a discussion of JIT usage. When JIT support
148 is enabled, pcre2grep automatically makes use of it, unless you add
149 --disable-pcre2grep-jit
151 to the "configure" command.
153
155 By default, PCRE2 interprets the linefeed (LF) character as indicating
157 the end of a line. This is the normal newline character on Unix-like
158 systems. You can compile PCRE2 to use carriage return (CR) instead, by
159 adding
160 --enable-newline-is-cr
162 to the configure command. There is also an --enable-newline-is-lf
164 option, which explicitly specifies linefeed as the newline character.
165 Alternatively, you can specify that line endings are to be indicated by
167 the two-character sequence CRLF (CR immediately followed by LF). If you
168 want this, add
169 --enable-newline-is-crlf
171 to the configure command. There is a fourth option, specified by
173 --enable-newline-is-anycrlf
175 which causes PCRE2 to recognize any of the three sequences CR, LF, or
177 CRLF as indicating a line ending. A fifth option, specified by
178 --enable-newline-is-any
180 causes PCRE2 to recognize any Unicode newline sequence. The Unicode
182 newline sequences are the three just mentioned, plus the single charac‐
183 ters VT (vertical tab, U+000B), FF (form feed, U+000C), NEL (next line,
184 U+0085), LS (line separator, U+2028), and PS (paragraph separator,
185 U+2029). The final option is
186 --enable-newline-is-nul
188 which causes NUL (binary zero) to be set as the default line-ending
190 character.
191 Whatever default line ending convention is selected when PCRE2 is built
193 can be overridden by applications that use the library. At build time
194 it is recommended to use the standard for your operating system.
195
197 By default, the sequence \R in a pattern matches any Unicode newline
199 sequence, independently of what has been selected as the line ending
200 sequence. If you specify
201 --enable-bsr-anycrlf
203 the default is changed so that \R matches only CR, LF, or CRLF. What‐
205 ever is selected when PCRE2 is built can be overridden by applications
206 that use the library.
207
209 Within a compiled pattern, offset values are used to point from one
211 part to another (for example, from an opening parenthesis to an alter‐
212 nation metacharacter). By default, in the 8-bit and 16-bit libraries,
213 two-byte values are used for these offsets, leading to a maximum size
214 for a compiled pattern of around 64 thousand code units. This is suffi‐
215 cient to handle all but the most gigantic patterns. Nevertheless, some
216 people do want to process truly enormous patterns, so it is possible to
217 compile PCRE2 to use three-byte or four-byte offsets by adding a set‐
218 ting such as
219 --with-link-size=3
221 to the configure command. The value given must be 2, 3, or 4. For the
223 16-bit library, a value of 3 is rounded up to 4. In these libraries,
224 using longer offsets slows down the operation of PCRE2 because it has
225 to load additional data when handling them. For the 32-bit library the
226 value is always 4 and cannot be overridden; the value of --with-link-
227 size is ignored.
228
230 The pcre2_match() function increments a counter each time it goes round
232 its main loop. Putting a limit on this counter controls the amount of
233 computing resource used by a single call to pcre2_match(). The limit
234 can be changed at run time, as described in the pcre2api documentation.
235 The default is 10 million, but this can be changed by adding a setting
236 such as
237 --with-match-limit=500000
239 to the configure command. This setting also applies to the
241 pcre2_dfa_match() matching function, and to JIT matching (though the
242 counting is done differently).
243 The pcre2_match() function starts out using a 20KiB vector on the sys‐
245 tem stack to record backtracking points. The more nested backtracking
246 points there are (that is, the deeper the search tree), the more memory
247 is needed. If the initial vector is not large enough, heap memory is
248 used, up to a certain limit, which is specified in kibibytes (units of
249 1024 bytes). The limit can be changed at run time, as described in the
250 pcre2api documentation. The default limit (in effect unlimited) is 20
251 million. You can change this by a setting such as
252 --with-heap-limit=500
254 which limits the amount of heap to 500 KiB. This limit applies only to
256 interpretive matching in pcre2_match() and pcre2_dfa_match(), which may
257 also use the heap for internal workspace when processing complicated
258 patterns. This limit does not apply when JIT (which has its own memory
259 arrangements) is used.
260 You can also explicitly limit the depth of nested backtracking in the
262 pcre2_match() interpreter. This limit defaults to the value that is set
263 for --with-match-limit. You can set a lower default limit by adding,
264 for example,
265 --with-match-limit_depth=10000
267 to the configure command. This value can be overridden at run time.
269 This depth limit indirectly limits the amount of heap memory that is
270 used, but because the size of each backtracking "frame" depends on the
271 number of capturing parentheses in a pattern, the amount of heap that
272 is used before the limit is reached varies from pattern to pattern.
273 This limit was more useful in versions before 10.30, where function
274 recursion was used for backtracking.
275 As well as applying to pcre2_match(), the depth limit also controls the
277 depth of recursive function calls in pcre2_dfa_match(). These are used
278 for lookaround assertions, atomic groups, and recursion within pat‐
279 terns. The limit does not apply to JIT matching.
280
282 PCRE2 uses fixed tables for processing characters whose code points are
284 less than 256. By default, PCRE2 is built with a set of tables that are
285 distributed in the file src/pcre2_chartables.c.dist. These tables are
286 for ASCII codes only. If you add
287 --enable-rebuild-chartables
289 to the configure command, the distributed tables are no longer used.
291 Instead, a program called dftables is compiled and run. This outputs
292 the source for new set of tables, created in the default locale of your
293 C run-time system. This method of replacing the tables does not work if
294 you are cross compiling, because dftables is run on the local host. If
295 you need to create alternative tables when cross compiling, you will
296 have to do so "by hand".
297
299 PCRE2 assumes by default that it will run in an environment where the
301 character code is ASCII or Unicode, which is a superset of ASCII. This
302 is the case for most computer operating systems. PCRE2 can, however, be
303 compiled to run in an 8-bit EBCDIC environment by adding
304 --enable-ebcdic --disable-unicode
306 to the configure command. This setting implies --enable-rebuild-charta‐
308 bles. You should only use it if you know that you are in an EBCDIC
309 environment (for example, an IBM mainframe operating system).
310 It is not possible to support both EBCDIC and UTF-8 codes in the same
312 version of the library. Consequently, --enable-unicode and --enable-
313 ebcdic are mutually exclusive.
314 The EBCDIC character that corresponds to an ASCII LF is assumed to have
316 the value 0x15 by default. However, in some EBCDIC environments, 0x25
317 is used. In such an environment you should use
318 --enable-ebcdic-nl25
320 as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR
322 has the same value as in ASCII, namely, 0x0d. Whichever of 0x15 and
323 0x25 is not chosen as LF is made to correspond to the Unicode NEL char‐
324 acter (which, in Unicode, is 0x85).
325 The options that select newline behaviour, such as --enable-newline-is-
327 cr, and equivalent run-time options, refer to these character values in
328 an EBCDIC environment.
329
331 By default, on non-Windows systems, pcre2grep supports the use of call‐
333 outs with string arguments within the patterns it is matching, in order
334 to run external scripts. For details, see the pcre2grep documentation.
335 This support can be disabled by adding --disable-pcre2grep-callout to
336 the configure command.
337
339 By default, pcre2grep reads all files as plain text. You can build it
341 so that it recognizes files whose names end in .gz or .bz2, and reads
342 them with libz or libbz2, respectively, by adding one or both of
343 --enable-pcre2grep-libz
345 --enable-pcre2grep-libbz2
346 to the configure command. These options naturally require that the rel‐
348 evant libraries are installed on your system. Configuration will fail
349 if they are not.
350
352 pcre2grep uses an internal buffer to hold a "window" on the file it is
354 scanning, in order to be able to output "before" and "after" lines when
355 it finds a match. The default starting size of the buffer is 20KiB. The
356 buffer itself is three times this size, but because of the way it is
357 used for holding "before" lines, the longest line that is guaranteed to
358 be processable is the notional buffer size. If a longer line is encoun‐
359 tered, pcre2grep automatically expands the buffer, up to a specified
360 maximum size, whose default is 1MiB or the starting size, whichever is
361 the larger. You can change the default parameter values by adding, for
362 example,
363 --with-pcre2grep-bufsize=51200
365 --with-pcre2grep-max-bufsize=2097152
366 to the configure command. The caller of pcre2grep can override these
368 values by using --buffer-size and --max-buffer-size on the command
369 line.
370
372 If you add one of
374 --enable-pcre2test-libreadline
376 --enable-pcre2test-libedit
377 to the configure command, pcre2test is linked with the libreadline
379 orlibedit library, respectively, and when its input is from a terminal,
380 it reads it using the readline() function. This provides line-editing
381 and history facilities. Note that libreadline is GPL-licensed, so if
382 you distribute a binary of pcre2test linked in this way, there may be
383 licensing issues. These can be avoided by linking instead with libedit,
384 which has a BSD licence.
385 Setting --enable-pcre2test-libreadline causes the -lreadline option to
387 be added to the pcre2test build. In many operating environments with a
388 sytem-installed readline library this is sufficient. However, in some
389 environments (e.g. if an unmodified distribution version of readline is
390 in use), some extra configuration may be necessary. The INSTALL file
391 for libreadline says this:
392 "Readline uses the termcap functions, but does not link with
394 the termcap or curses library itself, allowing applications
395 which link with readline the to choose an appropriate library."
396 If your environment has not been set up so that an appropriate library
398 is automatically included, you may need to add something like
399 LIBS="-ncurses"
401 immediately before the configure command.
403
405 If you add
407 --enable-debug
409 to the configure command, additional debugging code is included in the
411 build. This feature is intended for use by the PCRE2 maintainers.
412
414 If you add
416 --enable-valgrind
418 to the configure command, PCRE2 will use valgrind annotations to mark
420 certain memory regions as unaddressable. This allows it to detect
421 invalid memory accesses, and is mostly useful for debugging PCRE2
422 itself.
423
425 If your C compiler is gcc, you can build a version of PCRE2 that can
427 generate a code coverage report for its test suite. To enable this, you
428 must install lcov version 1.6 or above. Then specify
429 --enable-coverage
431 to the configure command and build PCRE2 in the usual way.
433 Note that using ccache (a caching C compiler) is incompatible with code
435 coverage reporting. If you have configured ccache to run automatically
436 on your system, you must set the environment variable
437 CCACHE_DISABLE=1
439 before running make to build PCRE2, so that ccache is not used.
441 When --enable-coverage is used, the following addition targets are
443 added to the Makefile:
444 make coverage
446 This creates a fresh coverage report for the PCRE2 test suite. It is
448 equivalent to running "make coverage-reset", "make coverage-baseline",
449 "make check", and then "make coverage-report".
450 make coverage-reset
452 This zeroes the coverage counters, but does nothing else.
454 make coverage-baseline
456 This captures baseline coverage information.
458 make coverage-report
460 This creates the coverage report.
462 make coverage-clean-report
464 This removes the generated coverage report without cleaning the cover‐
466 age data itself.
467 make coverage-clean-data
469 This removes the captured coverage data without removing the coverage
471 files created at compile time (*.gcno).
472 make coverage-clean
474 This cleans all coverage data including the generated coverage report.
476 For more information about code coverage, see the gcov and lcov docu‐
477 mentation.
478
480 There is a special option for use by people who want to run fuzzing
482 tests on PCRE2:
483 --enable-fuzz-support
485 At present this applies only to the 8-bit library. If set, it causes an
487 extra library called libpcre2-fuzzsupport.a to be built, but not
488 installed. This contains a single function called LLVMFuzzerTestOneIn‐
489 put() whose arguments are a pointer to a string and the length of the
490 string. When called, this function tries to compile the string as a
491 pattern, and if that succeeds, to match it. This is done both with no
492 options and with some random options bits that are generated from the
493 string.
494 Setting --enable-fuzz-support also causes a binary called pcre2fuz‐
496 zcheck to be created. This is normally run under valgrind or used when
497 PCRE2 is compiled with address sanitizing enabled. It calls the fuzzing
498 function and outputs information about what it is doing. The input
499 strings are specified by arguments: if an argument starts with "=" the
500 rest of it is a literal input string. Otherwise, it is assumed to be a
501 file name, and the contents of the file are the test string.
502
504 In versions of PCRE2 prior to 10.30, there were two ways of handling
506 backtracking in the pcre2_match() function. The default was to use the
507 system stack, but if
508 --disable-stack-for-recursion
510 was set, memory on the heap was used. From release 10.30 onwards this
512 has changed (the stack is no longer used) and this option now does
513 nothing except give a warning.
514
516 pcre2api(3), pcre2-config(3).
518
520 Philip Hazel
522 University Computing Service
523 Cambridge, England.
524
526 Last updated: 26 April 2018
528 Copyright (c) 1997-2018 University of Cambridge.
529PCRE2 10.32 26 April 2018 PCRE2BUILD(3)