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<html> |
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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-any |
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</pre> |
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which 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. Separate functions are provided because the usage is very |
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predictable: the block sizes requested are always the same, and the blocks are |
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always freed in reverse order. A calling program might be able to implement |
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optimized functions that perform better than the standard <b>malloc()</b> and |
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<b>free()</b> functions. PCRE runs noticeably more slowly when built in this |
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way. This option affects only the <b>pcre_exec()</b> function; it is not |
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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: 20 March 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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