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diff --git a/doc/pcrebuild.3 b/doc/pcrebuild.3 new file mode 100644 index 0000000..52ebefb --- /dev/null +++ b/doc/pcrebuild.3 @@ -0,0 +1,112 @@ +.TH PCRE 3 +.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. They are all selected, or deselected, by providing +options to the \fBconfigure\fR script which is run before the \fBmake\fR +command. The complete list of options for \fBconfigure\fR (which includes the +standard ones such as the selection of the installation directory) can be +obtained by running + + ./configure --help + +The following sections describe certain options whose names begin with --enable +or --disable. These settings specify changes to the defaults for the +\fBconfigure\fR command. Because of the way that \fBconfigure\fR 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 UTF-8 SUPPORT +.rs +.sp +To build PCRE with support for UTF-8 character strings, add + + --enable-utf8 + +to the \fBconfigure\fR command. Of itself, this does not make PCRE treat +strings as UTF-8. As well as compiling PCRE with this option, you also have +have to set the PCRE_UTF8 option when you call the \fBpcre_compile()\fR +function. + +.SH CODE VALUE OF NEWLINE +.rs +.sp +By default, PCRE treats character 10 (linefeed) as the newline character. This +is the normal newline character on Unix-like systems. You can compile PCRE to +use character 13 (carriage return) instead by adding + + --enable-newline-is-cr + +to the \fBconfigure\fR command. For completeness there is also a +--enable-newline-is-lf option, which explicitly specifies linefeed as the +newline character. + +.SH BUILDING SHARED AND STATIC LIBRARIES +.rs +.sp +The PCRE building process uses \fBlibtool\fR to build both shared and static +Unix libraries by default. You can suppress one of these by adding one of + + --disable-shared + --disable-static + +to the \fBconfigure\fR command, as required. + +.SH POSIX MALLOC USAGE +.rs +.sp +When PCRE is called through the POSIX interface (see the \fBpcreposix\fR +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()\fR 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 + + --with-posix-malloc-threshold=20 + +to the \fBconfigure\fR command. + +.SH LIMITING PCRE RESOURCE USAGE +.rs +.sp +Internally, PCRE has a function called \fBmatch()\fR which it calls repeatedly +(possibly recursively) when performing a matching operation. By limiting the +number of times this function may be called, a limit can be placed on the +resources used by a single call to \fBpcre_exec()\fR. The limit can be changed +at run time, as described in the \fBpcreapi\fR documentation. The default is 10 +million, but this can be changed by adding a setting such as + + --with-match-limit=500000 + +to the \fBconfigure\fR 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 enormous patterns, so it is possible to compile PCRE to use three-byte +or four-byte offsets by adding a setting such as + + --with-link-size=3 + +to the \fBconfigure\fR command. The value given must be 2, 3, or 4. Using +longer offsets slows down the operation of PCRE because it has to load +additional bytes when handling them. + +If you build PCRE with an increased link size, test 2 (and test 5 if you are +using UTF-8) will fail. Part of the output of these tests is a representation +of the compiled pattern, and this changes with the link size. + +.in 0 +Last updated: 21 January 2003 +.br +Copyright (c) 1997-2003 University of Cambridge. |