CVSROOT: /webcvs/grep Module name: grep Changes by: Jim Meyering <meyering> 20/01/02 18:18:45
Index: html_node/Known-Bugs.html =================================================================== RCS file: html_node/Known-Bugs.html diff -N html_node/Known-Bugs.html --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ html_node/Known-Bugs.html 2 Jan 2020 23:18:44 -0000 1.1 @@ -0,0 +1,96 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd";> +<html> +<!-- This manual is for grep, a pattern matching engine. + +Copyright (C) 1999-2002, 2005, 2008-2020 Free Software Foundation, +Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the section entitled +"GNU Free Documentation License". --> +<!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ --> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<title>Known Bugs (GNU Grep 3.4)</title> + +<meta name="description" content="Known Bugs (GNU Grep 3.4)"> +<meta name="keywords" content="Known Bugs (GNU Grep 3.4)"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Index.html#Index" rel="index" title="Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Reporting-Bugs.html#Reporting-Bugs" rel="up" title="Reporting Bugs"> +<link href="Copying.html#Copying" rel="next" title="Copying"> +<link href="Reporting-Bugs.html#Reporting-Bugs" rel="prev" title="Reporting Bugs"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.indentedblock {margin-right: 0em} +blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smalllisp {margin-left: 3.2em} +kbd {font-style: oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nolinebreak {white-space: nowrap} +span.roman {font-family: initial; font-weight: normal} +span.sansserif {font-family: sans-serif; font-weight: normal} +ul.no-bullet {list-style: none} +--> +</style> +<link rel="stylesheet" type="text/css" href="/software/gnulib/manual.css"> + + +</head> + +<body lang="en"> +<a name="Known-Bugs"></a> +<div class="header"> +<p> +Up: <a href="Reporting-Bugs.html#Reporting-Bugs" accesskey="u" rel="up">Reporting Bugs</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Known-Bugs-1"></a> +<h3 class="section">6.1 Known Bugs</h3> +<a name="index-Bugs_002c-known"></a> + +<p>Large repetition counts in the ‘<samp>{n,m}</samp>’ construct may cause +<code>grep</code> to use lots of memory. +In addition, certain other +obscure regular expressions require exponential time and +space, and may cause <code>grep</code> to run out of memory. +</p> +<p>Back-references can greatly slow down matching, as they can generate +exponentially many matching possibilities that can consume both time +and memory to explore. Also, the POSIX specification for +back-references is at times unclear. Furthermore, many regular +expression implementations have back-reference bugs that can cause +programs to return incorrect answers or even crash, and fixing these +bugs has often been low-priority—for example, as of 2019 the GNU C +library bug database contained back-reference bugs 52, 10844, 11053, +and 25322, with little sign of forthcoming fixes. Luckily, +back-references are rarely useful and it should be little trouble to +avoid them in practical applications. +</p> + + + + +</body> +</html>
