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diff --git a/8.31/doc/pcrebuild.3 b/8.31/doc/pcrebuild.3 new file mode 100644 index 0000000..52f97fb --- /dev/null +++ b/8.31/doc/pcrebuild.3 @@ -0,0 +1,425 @@ +.TH PCREBUILD 3 "07 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions +. +. +.SH "PCRE BUILD-TIME OPTIONS" +.rs +.sp +This document describes the optional features of PCRE that can be selected when +the library is compiled. It assumes use of the \fBconfigure\fP script, where +the optional features are selected or deselected by providing options to +\fBconfigure\fP before running the \fBmake\fP command. However, the same +options can be selected in both Unix-like and non-Unix-like environments using +the GUI facility of \fBcmake-gui\fP if you are using \fBCMake\fP instead of +\fBconfigure\fP to build PCRE. +.P +There is a lot more information about building PCRE in non-Unix-like +environments in the file called \fINON_UNIX_USE\fP, which is part of the PCRE +distribution. You should consult this file as well as the \fIREADME\fP file if +you are building in a non-Unix-like environment. +.P +The complete list of options for \fBconfigure\fP (which includes the standard +ones such as the selection of the installation directory) can be obtained by +running +.sp + ./configure --help +.sp +The following sections include descriptions of options whose names begin with +--enable or --disable. These settings specify changes to the defaults for the +\fBconfigure\fP command. Because of the way that \fBconfigure\fP 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. +. +. +.SH "BUILDING 8-BIT and 16-BIT LIBRARIES" +.rs +.sp +By default, a library called \fBlibpcre\fP is built, containing functions that +take string arguments contained in vectors of bytes, either as single-byte +characters, or interpreted as UTF-8 strings. You can also build a separate +library, called \fBlibpcre16\fP, in which strings are contained in vectors of +16-bit data units and interpreted either as single-unit characters or UTF-16 +strings, by adding +.sp + --enable-pcre16 +.sp +to the \fBconfigure\fP command. If you do not want the 8-bit library, add +.sp + --disable-pcre8 +.sp +as well. At least one of the two libraries must be built. Note that the C++ and +POSIX wrappers are for the 8-bit library only, and that \fBpcregrep\fP is an +8-bit program. None of these are built if you select only the 16-bit library. +. +. +.SH "BUILDING SHARED AND STATIC LIBRARIES" +.rs +.sp +The PCRE building process uses \fBlibtool\fP to build both shared and static +Unix libraries by default. You can suppress one of these by adding one of +.sp + --disable-shared + --disable-static +.sp +to the \fBconfigure\fP command, as required. +. +. +.SH "C++ SUPPORT" +.rs +.sp +By default, if the 8-bit library is being built, the \fBconfigure\fP script +will search for a C++ compiler and C++ header files. If it finds them, it +automatically builds the C++ wrapper library (which supports only 8-bit +strings). You can disable this by adding +.sp + --disable-cpp +.sp +to the \fBconfigure\fP command. +. +. +.SH "UTF-8 and UTF-16 SUPPORT" +.rs +.sp +To build PCRE with support for UTF Unicode character strings, add +.sp + --enable-utf +.sp +to the \fBconfigure\fP command. This setting applies to both libraries, adding +support for UTF-8 to the 8-bit library and support for UTF-16 to the 16-bit +library. There are no separate options for enabling UTF-8 and UTF-16 +independently because that would allow ridiculous settings such as requesting +UTF-16 support while building only the 8-bit library. It is not possible to +build one library with UTF support and the other without in the same +configuration. (For backwards compatibility, --enable-utf8 is a synonym of +--enable-utf.) +.P +Of itself, this setting does not make PCRE treat strings as UTF-8 or UTF-16. As +well as compiling PCRE with this option, you also have have to set the +PCRE_UTF8 or PCRE_UTF16 option when you call one of the pattern compiling +functions. +.P +If you set --enable-utf when compiling in an EBCDIC environment, PCRE expects +its input to be either ASCII or UTF-8 (depending on the run-time option). It is +not possible to support both EBCDIC and UTF-8 codes in the same version of the +library. Consequently, --enable-utf and --enable-ebcdic are mutually +exclusive. +. +. +.SH "UNICODE CHARACTER PROPERTY SUPPORT" +.rs +.sp +UTF support allows the libraries to process character codepoints up to 0x10ffff +in the strings that they handle. On its own, however, it does not provide any +facilities for accessing the properties of such characters. If you want to be +able to use the pattern escapes \eP, \ep, and \eX, which refer to Unicode +character properties, you must add +.sp + --enable-unicode-properties +.sp +to the \fBconfigure\fP command. This implies UTF support, even if you have +not explicitly requested it. +.P +Including Unicode property support adds around 30K of tables to the PCRE +library. Only the general category properties such as \fILu\fP and \fINd\fP are +supported. Details are given in the +.\" HREF +\fBpcrepattern\fP +.\" +documentation. +. +. +.SH "JUST-IN-TIME COMPILER SUPPORT" +.rs +.sp +Just-in-time compiler support is included in the build by specifying +.sp + --enable-jit +.sp +This support is available only for certain hardware architectures. If this +option is set for an unsupported architecture, a compile time error occurs. +See the +.\" HREF +\fBpcrejit\fP +.\" +documentation for a discussion of JIT usage. When JIT support is enabled, +pcregrep automatically makes use of it, unless you add +.sp + --disable-pcregrep-jit +.sp +to the "configure" command. +. +. +.SH "CODE VALUE OF NEWLINE" +.rs +.sp +By default, PCRE 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 PCRE to use carriage return (CR) instead, by adding +.sp + --enable-newline-is-cr +.sp +to the \fBconfigure\fP command. There is also a --enable-newline-is-lf option, +which explicitly specifies linefeed as the newline character. +.sp +Alternatively, you can specify that line endings are to be indicated by the two +character sequence CRLF. If you want this, add +.sp + --enable-newline-is-crlf +.sp +to the \fBconfigure\fP command. There is a fourth option, specified by +.sp + --enable-newline-is-anycrlf +.sp +which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as +indicating a line ending. Finally, a fifth option, specified by +.sp + --enable-newline-is-any +.sp +causes PCRE to recognize any Unicode newline sequence. +.P +Whatever line ending convention is selected when PCRE is built can be +overridden when the library functions are called. At build time it is +conventional to use the standard for your operating system. +. +. +.SH "WHAT \eR MATCHES" +.rs +.sp +By default, the sequence \eR in a pattern matches any Unicode newline sequence, +whatever has been selected as the line ending sequence. If you specify +.sp + --enable-bsr-anycrlf +.sp +the default is changed so that \eR matches only CR, LF, or CRLF. Whatever is +selected when PCRE is built can be overridden when the library functions are +called. +. +. +.SH "POSIX MALLOC USAGE" +.rs +.sp +When the 8-bit library is called through the POSIX interface (see the +.\" HREF +\fBpcreposix\fP +.\" +documentation), additional working storage is required for holding the pointers +to capturing substrings, because PCRE requires three integers per substring, +whereas the POSIX interface provides only two. If the number of expected +substrings is small, the wrapper function uses space on the stack, because this +is faster than using \fBmalloc()\fP for each call. The default threshold above +which the stack is no longer used is 10; it can be changed by adding a setting +such as +.sp + --with-posix-malloc-threshold=20 +.sp +to the \fBconfigure\fP command. +. +. +.SH "HANDLING VERY LARGE PATTERNS" +.rs +.sp +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, two-byte values are used for these offsets, leading +to a maximum size for a compiled pattern of around 64K. 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 PCRE to use +three-byte or four-byte offsets by adding a setting such as +.sp + --with-link-size=3 +.sp +to the \fBconfigure\fP command. The value given must be 2, 3, or 4. For the +16-bit library, a value of 3 is rounded up to 4. Using longer offsets slows +down the operation of PCRE because it has to load additional data when handling +them. +. +. +.SH "AVOIDING EXCESSIVE STACK USAGE" +.rs +.sp +When matching with the \fBpcre_exec()\fP function, PCRE implements backtracking +by making recursive calls to an internal function called \fBmatch()\fP. In +environments where the size of the stack is limited, this can severely limit +PCRE's operation. (The Unix environment does not usually suffer from this +problem, but it may sometimes be necessary to increase the maximum stack size. +There is a discussion in the +.\" HREF +\fBpcrestack\fP +.\" +documentation.) An alternative approach to recursion that uses memory from the +heap to remember data, instead of using recursive function calls, has been +implemented to work round the problem of limited stack size. If you want to +build a version of PCRE that works this way, add +.sp + --disable-stack-for-recursion +.sp +to the \fBconfigure\fP command. With this configuration, PCRE will use the +\fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP variables to call memory +management functions. By default these point to \fBmalloc()\fP and +\fBfree()\fP, but you can replace the pointers so that your own functions are +used instead. +.P +Separate functions are provided rather than using \fBpcre_malloc\fP and +\fBpcre_free\fP because the usage is very predictable: the block sizes +requested are always the same, and the blocks are always freed in reverse +order. A calling program might be able to implement optimized functions that +perform better than \fBmalloc()\fP and \fBfree()\fP. PCRE runs noticeably more +slowly when built in this way. This option affects only the \fBpcre_exec()\fP +function; it is not relevant for \fBpcre_dfa_exec()\fP. +. +. +.SH "LIMITING PCRE RESOURCE USAGE" +.rs +.sp +Internally, PCRE has a function called \fBmatch()\fP, which it calls repeatedly +(sometimes recursively) when matching a pattern with the \fBpcre_exec()\fP +function. By controlling the maximum number of times this function may be +called during a single matching operation, a limit can be placed on the +resources used by a single call to \fBpcre_exec()\fP. The limit can be changed +at run time, as described in the +.\" HREF +\fBpcreapi\fP +.\" +documentation. The default is 10 million, but this can be changed by adding a +setting such as +.sp + --with-match-limit=500000 +.sp +to the \fBconfigure\fP command. This setting has no effect on the +\fBpcre_dfa_exec()\fP matching function. +.P +In some environments it is desirable to limit the depth of recursive calls of +\fBmatch()\fP more strictly than the total number of calls, in order to +restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion +is specified) that is used. A second limit controls this; it defaults to the +value that is set for --with-match-limit, which imposes no additional +constraints. However, you can set a lower limit by adding, for example, +.sp + --with-match-limit-recursion=10000 +.sp +to the \fBconfigure\fP command. This value can also be overridden at run time. +. +. +.SH "CREATING CHARACTER TABLES AT BUILD TIME" +.rs +.sp +PCRE uses fixed tables for processing characters whose code values are less +than 256. By default, PCRE is built with a set of tables that are distributed +in the file \fIpcre_chartables.c.dist\fP. These tables are for ASCII codes +only. If you add +.sp + --enable-rebuild-chartables +.sp +to the \fBconfigure\fP command, the distributed tables are no longer used. +Instead, a program called \fBdftables\fP 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 \fBdftables\fP is run on the local host. If you need to +create alternative tables when cross compiling, you will have to do so "by +hand".) +. +. +.SH "USING EBCDIC CODE" +.rs +.sp +PCRE 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. PCRE can, however, be compiled to run in an +EBCDIC environment by adding +.sp + --enable-ebcdic +.sp +to the \fBconfigure\fP 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). The +--enable-ebcdic option is incompatible with --enable-utf. +. +. +.SH "PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT" +.rs +.sp +By default, \fBpcregrep\fP reads all files as plain text. You can build it so +that it recognizes files whose names end in \fB.gz\fP or \fB.bz2\fP, and reads +them with \fBlibz\fP or \fBlibbz2\fP, respectively, by adding one or both of +.sp + --enable-pcregrep-libz + --enable-pcregrep-libbz2 +.sp +to the \fBconfigure\fP command. These options naturally require that the +relevant libraries are installed on your system. Configuration will fail if +they are not. +. +. +.SH "PCREGREP BUFFER SIZE" +.rs +.sp +\fBpcregrep\fP 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 size of the buffer is controlled by a parameter whose +default value is 20K. 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 parameter size. You can change the default +parameter value by adding, for example, +.sp + --with-pcregrep-bufsize=50K +.sp +to the \fBconfigure\fP command. The caller of \fPpcregrep\fP can, however, +override this value by specifying a run-time option. +. +. +.SH "PCRETEST OPTION FOR LIBREADLINE SUPPORT" +.rs +.sp +If you add +.sp + --enable-pcretest-libreadline +.sp +to the \fBconfigure\fP command, \fBpcretest\fP is linked with the +\fBlibreadline\fP library, and when its input is from a terminal, it reads it +using the \fBreadline()\fP function. This provides line-editing and history +facilities. Note that \fBlibreadline\fP is GPL-licensed, so if you distribute a +binary of \fBpcretest\fP linked in this way, there may be licensing issues. +.P +Setting this option causes the \fB-lreadline\fP option to be added to the +\fBpcretest\fP build. In many operating environments with a sytem-installed +\fBlibreadline\fP 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 \fBlibreadline\fP says +this: +.sp + "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." +.sp +If your environment has not been set up so that an appropriate library is +automatically included, you may need to add something like +.sp + LIBS="-ncurses" +.sp +immediately before the \fBconfigure\fP command. +. +. +.SH "SEE ALSO" +.rs +.sp +\fBpcreapi\fP(3), \fBpcre16\fP, \fBpcre_config\fP(3). +. +. +.SH AUTHOR +.rs +.sp +.nf +Philip Hazel +University Computing Service +Cambridge CB2 3QH, England. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 07 January 2012 +Copyright (c) 1997-2012 University of Cambridge. +.fi |