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<title>pcrebuild specification</title>
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<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
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<h1>pcrebuild man page</h1>
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<p>
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Return to the <a href="index.html">PCRE index page</a>.
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</p>
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<p>
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This page is part of the PCRE HTML documentation. It was generated automatically
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from the original man page. If there is any nonsense in it, please consult the
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man page, in case the conversion went wrong.
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<br>
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<ul>
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<li><a name="TOC1" href="#SEC1">PCRE BUILD-TIME OPTIONS</a>
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<li><a name="TOC2" href="#SEC2">C++ SUPPORT</a>
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<li><a name="TOC3" href="#SEC3">UTF-8 SUPPORT</a>
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<li><a name="TOC4" href="#SEC4">UNICODE CHARACTER PROPERTY SUPPORT</a>
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<li><a name="TOC5" href="#SEC5">CODE VALUE OF NEWLINE</a>
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<li><a name="TOC6" href="#SEC6">BUILDING SHARED AND STATIC LIBRARIES</a>
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<li><a name="TOC7" href="#SEC7">POSIX MALLOC USAGE</a>
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<li><a name="TOC8" href="#SEC8">HANDLING VERY LARGE PATTERNS</a>
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<li><a name="TOC9" href="#SEC9">AVOIDING EXCESSIVE STACK USAGE</a>
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<li><a name="TOC10" href="#SEC10">LIMITING PCRE RESOURCE USAGE</a>
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<li><a name="TOC11" href="#SEC11">CREATING CHARACTER TABLES AT BUILD TIME</a>
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<li><a name="TOC12" href="#SEC12">USING EBCDIC CODE</a>
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<li><a name="TOC13" href="#SEC13">SEE ALSO</a>
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<li><a name="TOC14" href="#SEC14">AUTHOR</a>
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<li><a name="TOC15" href="#SEC15">REVISION</a>
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</ul>
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<br><a name="SEC1" href="#TOC1">PCRE BUILD-TIME OPTIONS</a><br>
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<P>
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This document describes the optional features of PCRE that can be selected when
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the library is compiled. They are all selected, or deselected, by providing
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options to the <b>configure</b> script that is run before the <b>make</b>
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command. The complete list of options for <b>configure</b> (which includes the
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standard ones such as the selection of the installation directory) can be
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obtained by running
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<pre>
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./configure --help
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</pre>
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The following sections include descriptions of options whose names begin with
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--enable or --disable. These settings specify changes to the defaults for the
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<b>configure</b> command. Because of the way that <b>configure</b> works,
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--enable and --disable always come in pairs, so the complementary option always
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exists as well, but as it specifies the default, it is not described.
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</P>
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<br><a name="SEC2" href="#TOC1">C++ SUPPORT</a><br>
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<P>
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By default, the <b>configure</b> script will search for a C++ compiler and C++
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header files. If it finds them, it automatically builds the C++ wrapper library
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for PCRE. You can disable this by adding
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<pre>
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--disable-cpp
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</pre>
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to the <b>configure</b> command.
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</P>
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<br><a name="SEC3" href="#TOC1">UTF-8 SUPPORT</a><br>
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<P>
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To build PCRE with support for UTF-8 character strings, add
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<pre>
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--enable-utf8
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</pre>
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to the <b>configure</b> command. Of itself, this does not make PCRE treat
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strings as UTF-8. As well as compiling PCRE with this option, you also have
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have to set the PCRE_UTF8 option when you call the <b>pcre_compile()</b>
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function.
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</P>
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<br><a name="SEC4" href="#TOC1">UNICODE CHARACTER PROPERTY SUPPORT</a><br>
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<P>
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UTF-8 support allows PCRE to process character values greater than 255 in the
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strings that it handles. On its own, however, it does not provide any
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facilities for accessing the properties of such characters. If you want to be
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able to use the pattern escapes \P, \p, and \X, which refer to Unicode
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character properties, you must add
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<pre>
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--enable-unicode-properties
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</pre>
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to the <b>configure</b> command. This implies UTF-8 support, even if you have
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not explicitly requested it.
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</P>
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<P>
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Including Unicode property support adds around 30K of tables to the PCRE
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library. Only the general category properties such as <i>Lu</i> and <i>Nd</i> are
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supported. Details are given in the
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<a href="pcrepattern.html"><b>pcrepattern</b></a>
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documentation.
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</P>
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<br><a name="SEC5" href="#TOC1">CODE VALUE OF NEWLINE</a><br>
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<P>
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By default, PCRE interprets character 10 (linefeed, LF) as indicating the end
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of a line. This is the normal newline character on Unix-like systems. You can
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compile PCRE to use character 13 (carriage return, CR) instead, by adding
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<pre>
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--enable-newline-is-cr
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</pre>
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to the <b>configure</b> command. There is also a --enable-newline-is-lf option,
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which explicitly specifies linefeed as the newline character.
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<br>
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<br>
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Alternatively, you can specify that line endings are to be indicated by the two
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character sequence CRLF. If you want this, add
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<pre>
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--enable-newline-is-crlf
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</pre>
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to the <b>configure</b> command. There is a fourth option, specified by
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<pre>
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--enable-newline-is-anycrlf
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</pre>
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which causes PCRE to recognize any of the three sequences CR, LF, or CRLF as
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indicating a line ending. Finally, a fifth option, specified by
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<pre>
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--enable-newline-is-any
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</pre>
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causes PCRE to recognize any Unicode newline sequence.
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</P>
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<P>
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Whatever line ending convention is selected when PCRE is built can be
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overridden when the library functions are called. At build time it is
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conventional to use the standard for your operating system.
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</P>
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<br><a name="SEC6" href="#TOC1">BUILDING SHARED AND STATIC LIBRARIES</a><br>
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<P>
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The PCRE building process uses <b>libtool</b> to build both shared and static
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Unix libraries by default. You can suppress one of these by adding one of
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<pre>
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--disable-shared
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--disable-static
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</pre>
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to the <b>configure</b> command, as required.
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</P>
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<br><a name="SEC7" href="#TOC1">POSIX MALLOC USAGE</a><br>
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<P>
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When PCRE is called through the POSIX interface (see the
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<a href="pcreposix.html"><b>pcreposix</b></a>
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documentation), additional working storage is required for holding the pointers
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to capturing substrings, because PCRE requires three integers per substring,
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whereas the POSIX interface provides only two. If the number of expected
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substrings is small, the wrapper function uses space on the stack, because this
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is faster than using <b>malloc()</b> for each call. The default threshold above
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which the stack is no longer used is 10; it can be changed by adding a setting
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such as
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<pre>
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--with-posix-malloc-threshold=20
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</pre>
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to the <b>configure</b> command.
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</P>
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<br><a name="SEC8" href="#TOC1">HANDLING VERY LARGE PATTERNS</a><br>
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<P>
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Within a compiled pattern, offset values are used to point from one part to
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another (for example, from an opening parenthesis to an alternation
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metacharacter). By default, two-byte values are used for these offsets, leading
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to a maximum size for a compiled pattern of around 64K. This is sufficient to
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handle all but the most gigantic patterns. Nevertheless, some people do want to
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process enormous patterns, so it is possible to compile PCRE to use three-byte
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or four-byte offsets by adding a setting such as
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<pre>
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--with-link-size=3
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</pre>
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to the <b>configure</b> command. The value given must be 2, 3, or 4. Using
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longer offsets slows down the operation of PCRE because it has to load
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additional bytes when handling them.
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</P>
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<br><a name="SEC9" href="#TOC1">AVOIDING EXCESSIVE STACK USAGE</a><br>
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<P>
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When matching with the <b>pcre_exec()</b> function, PCRE implements backtracking
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by making recursive calls to an internal function called <b>match()</b>. In
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environments where the size of the stack is limited, this can severely limit
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PCRE's operation. (The Unix environment does not usually suffer from this
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problem, but it may sometimes be necessary to increase the maximum stack size.
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There is a discussion in the
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<a href="pcrestack.html"><b>pcrestack</b></a>
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documentation.) An alternative approach to recursion that uses memory from the
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heap to remember data, instead of using recursive function calls, has been
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implemented to work round the problem of limited stack size. If you want to
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build a version of PCRE that works this way, add
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<pre>
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--disable-stack-for-recursion
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</pre>
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to the <b>configure</b> command. With this configuration, PCRE will use the
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<b>pcre_stack_malloc</b> and <b>pcre_stack_free</b> variables to call memory
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management functions. By default these point to <b>malloc()</b> and
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<b>free()</b>, but you can replace the pointers so that your own functions are
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used.
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</P>
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<P>
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Separate functions are provided rather than using <b>pcre_malloc</b> and
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<b>pcre_free</b> because the usage is very predictable: the block sizes
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requested are always the same, and the blocks are always freed in reverse
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order. A calling program might be able to implement optimized functions that
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perform better than <b>malloc()</b> and <b>free()</b>. PCRE runs noticeably more
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slowly when built in this way. This option affects only the <b>pcre_exec()</b>
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function; it is not relevant for the the <b>pcre_dfa_exec()</b> function.
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</P>
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<br><a name="SEC10" href="#TOC1">LIMITING PCRE RESOURCE USAGE</a><br>
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<P>
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Internally, PCRE has a function called <b>match()</b>, which it calls repeatedly
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(sometimes recursively) when matching a pattern with the <b>pcre_exec()</b>
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function. By controlling the maximum number of times this function may be
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called during a single matching operation, a limit can be placed on the
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resources used by a single call to <b>pcre_exec()</b>. The limit can be changed
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at run time, as described in the
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<a href="pcreapi.html"><b>pcreapi</b></a>
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documentation. The default is 10 million, but this can be changed by adding a
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setting such as
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<pre>
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--with-match-limit=500000
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</pre>
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to the <b>configure</b> command. This setting has no effect on the
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<b>pcre_dfa_exec()</b> matching function.
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</P>
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<P>
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In some environments it is desirable to limit the depth of recursive calls of
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<b>match()</b> more strictly than the total number of calls, in order to
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restrict the maximum amount of stack (or heap, if --disable-stack-for-recursion
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is specified) that is used. A second limit controls this; it defaults to the
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value that is set for --with-match-limit, which imposes no additional
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constraints. However, you can set a lower limit by adding, for example,
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<pre>
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--with-match-limit-recursion=10000
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</pre>
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to the <b>configure</b> command. This value can also be overridden at run time.
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</P>
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<br><a name="SEC11" href="#TOC1">CREATING CHARACTER TABLES AT BUILD TIME</a><br>
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<P>
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PCRE uses fixed tables for processing characters whose code values are less
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than 256. By default, PCRE is built with a set of tables that are distributed
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in the file <i>pcre_chartables.c.dist</i>. These tables are for ASCII codes
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only. If you add
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<pre>
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--enable-rebuild-chartables
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</pre>
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to the <b>configure</b> command, the distributed tables are no longer used.
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Instead, a program called <b>dftables</b> is compiled and run. This outputs the
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source for new set of tables, created in the default locale of your C runtime
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system. (This method of replacing the tables does not work if you are cross
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compiling, because <b>dftables</b> is run on the local host. If you need to
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create alternative tables when cross compiling, you will have to do so "by
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hand".)
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</P>
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<br><a name="SEC12" href="#TOC1">USING EBCDIC CODE</a><br>
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<P>
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PCRE assumes by default that it will run in an environment where the character
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code is ASCII (or Unicode, which is a superset of ASCII). PCRE can, however, be
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compiled to run in an EBCDIC environment by adding
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<pre>
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--enable-ebcdic
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</pre>
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to the <b>configure</b> command. This setting implies
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--enable-rebuild-chartables.
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</P>
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<br><a name="SEC13" href="#TOC1">SEE ALSO</a><br>
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<P>
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<b>pcreapi</b>(3), <b>pcre_config</b>(3).
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</P>
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<br><a name="SEC14" href="#TOC1">AUTHOR</a><br>
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<P>
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Philip Hazel
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<br>
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University Computing Service
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<br>
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Cambridge CB2 3QH, England.
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<br>
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</P>
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<br><a name="SEC15" href="#TOC1">REVISION</a><br>
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<P>
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Last updated: 05 June 2007
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<br>
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Copyright © 1997-2007 University of Cambridge.
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<br>
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<p>
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Return to the <a href="index.html">PCRE index page</a>.
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</p>
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