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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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diff --git a/share/doc/cpp/Standard-Predefined-Macros.html b/share/doc/cpp/Standard-Predefined-Macros.html new file mode 100644 index 0000000..df3bda8 --- /dev/null +++ b/share/doc/cpp/Standard-Predefined-Macros.html @@ -0,0 +1,240 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1987-2023 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. A copy of +the license is included in the +section entitled "GNU Free Documentation License". + +This manual contains no Invariant Sections. The Front-Cover Texts are +(a) (see below), and the Back-Cover Texts are (b) (see below). + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>The C Preprocessor: Standard Predefined Macros</title> + +<meta name="description" content="The C Preprocessor: Standard Predefined Macros"> +<meta name="keywords" content="The C Preprocessor: Standard Predefined Macros"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Index-of-Directives.html#Index-of-Directives" rel="index" title="Index of Directives"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Predefined-Macros.html#Predefined-Macros" rel="up" title="Predefined Macros"> +<link href="Common-Predefined-Macros.html#Common-Predefined-Macros" rel="next" title="Common Predefined Macros"> +<link href="Predefined-Macros.html#Predefined-Macros" rel="previous" title="Predefined Macros"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +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.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Standard-Predefined-Macros"></a> +<div class="header"> +<p> +Next: <a href="Common-Predefined-Macros.html#Common-Predefined-Macros" accesskey="n" rel="next">Common Predefined Macros</a>, Up: <a href="Predefined-Macros.html#Predefined-Macros" accesskey="u" rel="up">Predefined Macros</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> +</div> +<hr> +<a name="Standard-Predefined-Macros-1"></a> +<h4 class="subsection">3.7.1 Standard Predefined Macros</h4> +<a name="index-standard-predefined-macros_002e"></a> + +<p>The standard predefined macros are specified by the relevant +language standards, so they are available with all compilers that +implement those standards. Older compilers may not provide all of +them. Their names all start with double underscores. +</p> +<dl compact="compact"> +<dt><code>__FILE__</code></dt> +<dd><p>This macro expands to the name of the current input file, in the form of +a C string constant. This is the path by which the preprocessor opened +the file, not the short name specified in ‘<samp>#include</samp>’ or as the +input file name argument. For example, +<code>"/usr/local/include/myheader.h"</code> is a possible expansion of this +macro. +</p> +</dd> +<dt><code>__LINE__</code></dt> +<dd><p>This macro expands to the current input line number, in the form of a +decimal integer constant. While we call it a predefined macro, it’s +a pretty strange macro, since its “definition” changes with each +new line of source code. +</p></dd> +</dl> + +<p><code>__FILE__</code> and <code>__LINE__</code> are useful in generating an error +message to report an inconsistency detected by the program; the message +can state the source line at which the inconsistency was detected. For +example, +</p> +<div class="smallexample"> +<pre class="smallexample">fprintf (stderr, "Internal error: " + "negative string length " + "%d at %s, line %d.", + length, __FILE__, __LINE__); +</pre></div> + +<p>An ‘<samp>#include</samp>’ directive changes the expansions of <code>__FILE__</code> +and <code>__LINE__</code> to correspond to the included file. At the end of +that file, when processing resumes on the input file that contained +the ‘<samp>#include</samp>’ directive, the expansions of <code>__FILE__</code> and +<code>__LINE__</code> revert to the values they had before the +‘<samp>#include</samp>’ (but <code>__LINE__</code> is then incremented by one as +processing moves to the line after the ‘<samp>#include</samp>’). +</p> +<p>A ‘<samp>#line</samp>’ directive changes <code>__LINE__</code>, and may change +<code>__FILE__</code> as well. See <a href="Line-Control.html#Line-Control">Line Control</a>. +</p> +<p>C99 introduced <code>__func__</code>, and GCC has provided <code>__FUNCTION__</code> +for a long time. Both of these are strings containing the name of the +current function (there are slight semantic differences; see the GCC +manual). Neither of them is a macro; the preprocessor does not know the +name of the current function. They tend to be useful in conjunction +with <code>__FILE__</code> and <code>__LINE__</code>, though. +</p> +<dl compact="compact"> +<dt><code>__DATE__</code></dt> +<dd><p>This macro expands to a string constant that describes the date on which +the preprocessor is being run. The string constant contains eleven +characters and looks like <code>"Feb 12 1996"<!-- /@w --></code>. If the day of the +month is less than 10, it is padded with a space on the left. +</p> +<p>If GCC cannot determine the current date, it will emit a warning message +(once per compilation) and <code>__DATE__</code> will expand to +<code>"??? ?? ????"<!-- /@w --></code>. +</p> +</dd> +<dt><code>__TIME__</code></dt> +<dd><p>This macro expands to a string constant that describes the time at +which the preprocessor is being run. The string constant contains +eight characters and looks like <code>"23:59:01"</code>. +</p> +<p>If GCC cannot determine the current time, it will emit a warning message +(once per compilation) and <code>__TIME__</code> will expand to +<code>"??:??:??"</code>. +</p> +</dd> +<dt><code>__STDC__</code></dt> +<dd><p>In normal operation, this macro expands to the constant 1, to signify +that this compiler conforms to ISO Standard C. If GNU CPP is used with +a compiler other than GCC, this is not necessarily true; however, the +preprocessor always conforms to the standard unless the +<samp>-traditional-cpp</samp> option is used. +</p> +<p>This macro is not defined if the <samp>-traditional-cpp</samp> option is used. +</p> +<p>On some hosts, the system compiler uses a different convention, where +<code>__STDC__</code> is normally 0, but is 1 if the user specifies strict +conformance to the C Standard. CPP follows the host convention when +processing system header files, but when processing user files +<code>__STDC__</code> is always 1. This has been reported to cause problems; +for instance, some versions of Solaris provide X Windows headers that +expect <code>__STDC__</code> to be either undefined or 1. See <a href="Invocation.html#Invocation">Invocation</a>. +</p> +</dd> +<dt><code>__STDC_VERSION__</code></dt> +<dd><p>This macro expands to the C Standard’s version number, a long integer +constant of the form <code><var>yyyy</var><var>mm</var>L</code> where <var>yyyy</var> and +<var>mm</var> are the year and month of the Standard version. This signifies +which version of the C Standard the compiler conforms to. Like +<code>__STDC__</code>, this is not necessarily accurate for the entire +implementation, unless GNU CPP is being used with GCC. +</p> +<p>The value <code>199409L</code> signifies the 1989 C standard as amended in +1994, which is the current default; the value <code>199901L</code> signifies +the 1999 revision of the C standard; the value <code>201112L</code> +signifies the 2011 revision of the C standard; the value +<code>201710L</code> signifies the 2017 revision of the C standard (which is +otherwise identical to the 2011 version apart from correction of +defects). An unspecified value larger than <code>201710L</code> is used for +the experimental <samp>-std=c2x</samp> and <samp>-std=gnu2x</samp> modes. +</p> +<p>This macro is not defined if the <samp>-traditional-cpp</samp> option is +used, nor when compiling C++ or Objective-C. +</p> +</dd> +<dt><code>__STDC_HOSTED__</code></dt> +<dd><p>This macro is defined, with value 1, if the compiler’s target is a +<em>hosted environment</em>. A hosted environment has the complete +facilities of the standard C library available. +</p> +</dd> +<dt><code>__cplusplus</code></dt> +<dd><p>This macro is defined when the C++ compiler is in use. You can use +<code>__cplusplus</code> to test whether a header is compiled by a C compiler +or a C++ compiler. This macro is similar to <code>__STDC_VERSION__</code>, in +that it expands to a version number. Depending on the language standard +selected, the value of the macro is +<code>199711L</code> for the 1998 C++ standard, +<code>201103L</code> for the 2011 C++ standard, +<code>201402L</code> for the 2014 C++ standard, +<code>201703L</code> for the 2017 C++ standard, +<code>202002L</code> for the 2020 C++ standard, +or an unspecified value strictly larger than <code>202002L</code> for the +experimental languages enabled by <samp>-std=c++23</samp> and +<samp>-std=gnu++23</samp>. +</p> +</dd> +<dt><code>__OBJC__</code></dt> +<dd><p>This macro is defined, with value 1, when the Objective-C compiler is in +use. You can use <code>__OBJC__</code> to test whether a header is compiled +by a C compiler or an Objective-C compiler. +</p> +</dd> +<dt><code>__ASSEMBLER__</code></dt> +<dd><p>This macro is defined with value 1 when preprocessing assembly +language. +</p> +</dd> +</dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Common-Predefined-Macros.html#Common-Predefined-Macros" accesskey="n" rel="next">Common Predefined Macros</a>, Up: <a href="Predefined-Macros.html#Predefined-Macros" accesskey="u" rel="up">Predefined Macros</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> +</div> + + + +</body> +</html> |