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152 lines
6.8 KiB
HTML
152 lines
6.8 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) 1987-2018 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. A copy of
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the license is included in the
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section entitled "GNU Free Documentation License".
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This manual contains no Invariant Sections. The Front-Cover Texts are
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(a) (see below), and the Back-Cover Texts are (b) (see below).
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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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>Implementation limits (The C Preprocessor)</title>
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<meta name="description" content="Implementation limits (The C Preprocessor)">
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<meta name="keywords" content="Implementation limits (The C Preprocessor)">
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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="Index-of-Directives.html#Index-of-Directives" rel="index" title="Index of Directives">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Implementation-Details.html#Implementation-Details" rel="up" title="Implementation Details">
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<link href="Obsolete-Features.html#Obsolete-Features" rel="next" title="Obsolete Features">
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<link href="Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior" rel="prev" title="Implementation-defined behavior">
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<style type="text/css">
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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="Implementation-limits"></a>
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<div class="header">
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<p>
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Next: <a href="Obsolete-Features.html#Obsolete-Features" accesskey="n" rel="next">Obsolete Features</a>, Previous: <a href="Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior" accesskey="p" rel="prev">Implementation-defined behavior</a>, Up: <a href="Implementation-Details.html#Implementation-Details" accesskey="u" rel="up">Implementation Details</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Implementation-limits-1"></a>
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<h3 class="section">11.2 Implementation limits</h3>
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<a name="index-implementation-limits"></a>
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<p>CPP has a small number of internal limits. This section lists the
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limits which the C standard requires to be no lower than some minimum,
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and all the others known. It is intended that there should be as few limits
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as possible. If you encounter an undocumented or inconvenient limit,
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please report that as a bug. See <a href="http://gcc.gnu.org/onlinedocs/gcc/Bugs.html#Bugs">Reporting Bugs</a> in <cite>Using
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the GNU Compiler Collection (GCC)</cite>.
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</p>
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<p>Where we say something is limited <em>only by available memory</em>, that
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means that internal data structures impose no intrinsic limit, and space
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is allocated with <code>malloc</code> or equivalent. The actual limit will
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therefore depend on many things, such as the size of other things
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allocated by the compiler at the same time, the amount of memory
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consumed by other processes on the same computer, etc.
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</p>
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<ul>
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<li> Nesting levels of ‘<samp>#include</samp>’ files.
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<p>We impose an arbitrary limit of 200 levels, to avoid runaway recursion.
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The standard requires at least 15 levels.
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</p>
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</li><li> Nesting levels of conditional inclusion.
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<p>The C standard mandates this be at least 63. CPP is limited only by
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available memory.
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</p>
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</li><li> Levels of parenthesized expressions within a full expression.
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<p>The C standard requires this to be at least 63. In preprocessor
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conditional expressions, it is limited only by available memory.
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</p>
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</li><li> Significant initial characters in an identifier or macro name.
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<p>The preprocessor treats all characters as significant. The C standard
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requires only that the first 63 be significant.
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</p>
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</li><li> Number of macros simultaneously defined in a single translation unit.
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<p>The standard requires at least 4095 be possible. CPP is limited only
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by available memory.
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</p>
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</li><li> Number of parameters in a macro definition and arguments in a macro call.
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<p>We allow <code>USHRT_MAX</code>, which is no smaller than 65,535. The minimum
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required by the standard is 127.
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</p>
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</li><li> Number of characters on a logical source line.
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<p>The C standard requires a minimum of 4096 be permitted. CPP places
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no limits on this, but you may get incorrect column numbers reported in
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diagnostics for lines longer than 65,535 characters.
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</p>
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</li><li> Maximum size of a source file.
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<p>The standard does not specify any lower limit on the maximum size of a
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source file. GNU cpp maps files into memory, so it is limited by the
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available address space. This is generally at least two gigabytes.
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Depending on the operating system, the size of physical memory may or
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may not be a limitation.
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</p>
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</li></ul>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Obsolete-Features.html#Obsolete-Features" accesskey="n" rel="next">Obsolete Features</a>, Previous: <a href="Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior" accesskey="p" rel="prev">Implementation-defined behavior</a>, Up: <a href="Implementation-Details.html#Implementation-Details" accesskey="u" rel="up">Implementation Details</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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