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100 lines
4.3 KiB
HTML
100 lines
4.3 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Free Software" and "Free Software Needs
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Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: "You are free to copy and modify
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this GNU Manual. Buying copies from GNU Press supports the FSF in
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developing GNU and promoting software freedom." -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Deviations (Debugging with GDB)</title>
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<meta name="description" content="Deviations (Debugging with GDB)">
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<meta name="keywords" content="Deviations (Debugging with GDB)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Modula_002d2.html#Modula_002d2" rel="up" title="Modula-2">
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<link href="M2-Checks.html#M2-Checks" rel="next" title="M2 Checks">
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<link href="M2-Defaults.html#M2-Defaults" rel="prev" title="M2 Defaults">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Deviations"></a>
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<div class="header">
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<p>
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Next: <a href="M2-Checks.html#M2-Checks" accesskey="n" rel="next">M2 Checks</a>, Previous: <a href="M2-Defaults.html#M2-Defaults" accesskey="p" rel="prev">M2 Defaults</a>, Up: <a href="Modula_002d2.html#Modula_002d2" accesskey="u" rel="up">Modula-2</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Deviations-from-Standard-Modula_002d2"></a>
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<h4 class="subsubsection">15.4.9.6 Deviations from Standard Modula-2</h4>
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<a name="index-Modula_002d2_002c-deviations-from"></a>
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<p>A few changes have been made to make Modula-2 programs easier to debug.
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This is done primarily via loosening its type strictness:
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</p>
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<ul>
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<li> Unlike in standard Modula-2, pointer constants can be formed by
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integers. This allows you to modify pointer variables during
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debugging. (In standard Modula-2, the actual address contained in a
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pointer variable is hidden from you; it can only be modified
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through direct assignment to another pointer variable or expression that
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returned a pointer.)
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</li><li> C escape sequences can be used in strings and characters to represent
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non-printable characters. <small>GDB</small> prints out strings with these
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escape sequences embedded. Single non-printable characters are
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printed using the ‘<samp>CHR(<var>nnn</var>)</samp>’ format.
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</li><li> The assignment operator (<code>:=</code>) returns the value of its right-hand
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argument.
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</li><li> All built-in procedures both modify <em>and</em> return their argument.
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</li></ul>
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</body>
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</html>
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