<html> <head> <title>pcrebuild specification</title> </head> <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> This HTML document has been generated automatically from the original man page. If there is any nonsense in it, please consult the man page, in case the conversion went wrong.<br> <ul> <li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a> <li><a name="TOC2" href="#SEC2">UTF-8 SUPPORT</a> <li><a name="TOC3" href="#SEC3">CODE VALUE OF NEWLINE</a> <li><a name="TOC4" href="#SEC4">BUILDING SHARED AND STATIC LIBRARIES</a> <li><a name="TOC5" href="#SEC5">POSIX MALLOC USAGE</a> <li><a name="TOC6" href="#SEC6">LIMITING PCRE RESOURCE USAGE</a> <li><a name="TOC7" href="#SEC7">HANDLING VERY LARGE PATTERNS</a> <li><a name="TOC8" href="#SEC8">AVOIDING EXCESSIVE STACK USAGE</a> <li><a name="TOC9" href="#SEC9">USING EBCDIC CODE</a> </ul> <br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br> <P> 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 <b>configure</b> script which is run before the <b>make</b> command. The complete list of options for <b>configure</b> (which includes the standard ones such as the selection of the installation directory) can be obtained by running </P> <P> <pre> ./configure --help </PRE> </P> <P> The following sections describe certain options whose names begin with --enable or --disable. These settings specify changes to the defaults for the <b>configure</b> command. Because of the way that <b>configure</b> 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. </P> <br><a name="SEC2" href="#TOC1">UTF-8 SUPPORT</a><br> <P> To build PCRE with support for UTF-8 character strings, add </P> <P> <pre> --enable-utf8 </PRE> </P> <P> to the <b>configure</b> 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 <b>pcre_compile()</b> function. </P> <br><a name="SEC3" href="#TOC1">CODE VALUE OF NEWLINE</a><br> <P> 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 </P> <P> <pre> --enable-newline-is-cr </PRE> </P> <P> to the <b>configure</b> command. For completeness there is also a --enable-newline-is-lf option, which explicitly specifies linefeed as the newline character. </P> <br><a name="SEC4" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br> <P> The PCRE building process uses <b>libtool</b> to build both shared and static Unix libraries by default. You can suppress one of these by adding one of </P> <P> <pre> --disable-shared --disable-static </PRE> </P> <P> to the <b>configure</b> command, as required. </P> <br><a name="SEC5" href="#TOC1">POSIX MALLOC USAGE</a><br> <P> When PCRE is called through the POSIX interface (see the <b>pcreposix</b> 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 <b>malloc()</b> 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 </P> <P> <pre> --with-posix-malloc-threshold=20 </PRE> </P> <P> to the <b>configure</b> command. </P> <br><a name="SEC6" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br> <P> Internally, PCRE has a function called <b>match()</b> 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 <b>pcre_exec()</b>. The limit can be changed at run time, as described in the <b>pcreapi</b> documentation. The default is 10 million, but this can be changed by adding a setting such as </P> <P> <pre> --with-match-limit=500000 </PRE> </P> <P> to the <b>configure</b> command. </P> <br><a name="SEC7" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br> <P> 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 </P> <P> <pre> --with-link-size=3 </PRE> </P> <P> to the <b>configure</b> 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. </P> <P> 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. </P> <br><a name="SEC8" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br> <P> PCRE implements backtracking while matching by making recursive calls to an internal function called <b>match()</b>. 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.) An alternative approach that uses memory from the heap to remember data, instead of using recursive function calls, has been implemented to work round this problem. If you want to build a version of PCRE that works this way, add </P> <P> <pre> --disable-stack-for-recursion </PRE> </P> <P> to the <b>configure</b> command. With this configuration, PCRE will use the <b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory management functions. Separate functions are provided 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 the standard <b>malloc()</b> and <b>free()</b> functions. PCRE runs noticeably more slowly when built in this way. </P> <br><a name="SEC9" href="#TOC1">USING EBCDIC CODE</a><br> <P> PCRE assumes by default that it will run in an environment where the character code is ASCII (or UTF-8, which is a superset of ASCII). PCRE can, however, be compiled to run in an EBCDIC environment by adding </P> <P> <pre> --enable-ebcdic </PRE> </P> <P> to the <b>configure</b> command. </P> <P> Last updated: 09 December 2003 <br> Copyright © 1997-2003 University of Cambridge.
