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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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| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gcc/Standards.html | |
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diff --git a/share/doc/gcc/Standards.html b/share/doc/gcc/Standards.html new file mode 100644 index 0000000..cbd5459 --- /dev/null +++ b/share/doc/gcc/Standards.html @@ -0,0 +1,424 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +Copyright (C) 1988-2023 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; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(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>Using the GNU Compiler Collection (GCC): Standards</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Standards"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Standards"> +<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="Indices.html#Indices" rel="index" title="Indices"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="index.html#Top" rel="up" title="Top"> +<link href="Invoking-GCC.html#Invoking-GCC" rel="next" title="Invoking GCC"> +<link href="G_002b_002b-and-GCC.html#G_002b_002b-and-GCC" rel="previous" title="G++ and GCC"> +<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_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Standards"></a> +<div class="header"> +<p> +Next: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="n" rel="next">Invoking GCC</a>, Previous: <a href="G_002b_002b-and-GCC.html#G_002b_002b-and-GCC" accesskey="p" rel="previous">G++ and GCC</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Language-Standards-Supported-by-GCC"></a> +<h2 class="chapter">2 Language Standards Supported by GCC</h2> + +<p>For each language compiled by GCC for which there is a standard, GCC +attempts to follow one or more versions of that standard, possibly +with some exceptions, and possibly with some extensions. +</p> +<a name="C-Language"></a> +<h3 class="section">2.1 C Language</h3> +<a name="index-C-standard"></a> +<a name="index-C-standards"></a> +<a name="index-ANSI-C-standard"></a> +<a name="index-ANSI-C"></a> +<a name="index-ANSI-C89"></a> +<a name="index-C89"></a> +<a name="index-ANSI-X3_002e159_002d1989"></a> +<a name="index-X3_002e159_002d1989"></a> +<a name="index-ISO-C-standard"></a> +<a name="index-ISO-C"></a> +<a name="index-ISO-C90"></a> +<a name="index-ISO_002fIEC-9899"></a> +<a name="index-ISO-9899"></a> +<a name="index-C90"></a> +<a name="index-ISO-C94"></a> +<a name="index-C94"></a> +<a name="index-ISO-C95"></a> +<a name="index-C95"></a> +<a name="index-ISO-C99"></a> +<a name="index-C99"></a> +<a name="index-ISO-C9X"></a> +<a name="index-C9X"></a> +<a name="index-ISO-C11"></a> +<a name="index-C11"></a> +<a name="index-ISO-C1X"></a> +<a name="index-C1X"></a> +<a name="index-ISO-C17"></a> +<a name="index-C17"></a> +<a name="index-ISO-C2X"></a> +<a name="index-C2X"></a> +<a name="index-Technical-Corrigenda"></a> +<a name="index-TC1"></a> +<a name="index-Technical-Corrigendum-1"></a> +<a name="index-TC2"></a> +<a name="index-Technical-Corrigendum-2"></a> +<a name="index-TC3"></a> +<a name="index-Technical-Corrigendum-3"></a> +<a name="index-AMD1"></a> +<a name="index-freestanding-implementation"></a> +<a name="index-freestanding-environment"></a> +<a name="index-hosted-implementation"></a> +<a name="index-hosted-environment"></a> +<a name="index-_005f_005fSTDC_005fHOSTED_005f_005f"></a> + +<a name="index-std"></a> +<a name="index-ansi"></a> +<a name="index-pedantic"></a> +<a name="index-pedantic_002derrors"></a> +<p>The original ANSI C standard (X3.159-1989) was ratified in 1989 and +published in 1990. This standard was ratified as an ISO standard +(ISO/IEC 9899:1990) later in 1990. There were no technical +differences between these publications, although the sections of the +ANSI standard were renumbered and became clauses in the ISO standard. +The ANSI +standard, but not the ISO standard, also came with a Rationale +document. +This standard, in both its forms, is commonly known as <em>C89</em>, or +occasionally as <em>C90</em>, from the dates of ratification. +To select this standard in GCC, use one of the options +<samp>-ansi</samp>, <samp>-std=c90</samp> or <samp>-std=iso9899:1990</samp>; to obtain +all the diagnostics required by the standard, you should also specify +<samp>-pedantic</samp> (or <samp>-pedantic-errors</samp> if you want them to be +errors rather than warnings). See <a href="C-Dialect-Options.html#C-Dialect-Options">Options +Controlling C Dialect</a>. +</p> +<p>Errors in the 1990 ISO C standard were corrected in two Technical +Corrigenda published in 1994 and 1996. GCC does not support the +uncorrected version. +</p> +<p>An amendment to the 1990 standard was published in 1995. This +amendment added digraphs and <code>__STDC_VERSION__</code> to the language, +but otherwise concerned the library. This amendment is commonly known +as <em>AMD1</em>; the amended standard is sometimes known as <em>C94</em> or +<em>C95</em>. To select this standard in GCC, use the option +<samp>-std=iso9899:199409</samp> (with, as for other standard versions, +<samp>-pedantic</samp> to receive all required diagnostics). +</p> +<p>A new edition of the ISO C standard was published in 1999 as ISO/IEC +9899:1999, and is commonly known as <em>C99</em>. (While in +development, drafts of this standard version were referred to as +<em>C9X</em>.) GCC has substantially +complete support for this standard version; see +<a href="https://gcc.gnu.org/c99status.html">https://gcc.gnu.org/c99status.html</a> for details. To select this +standard, use <samp>-std=c99</samp> or <samp>-std=iso9899:1999</samp>. +</p> +<p>Errors in the 1999 ISO C standard were corrected in three Technical +Corrigenda published in 2001, 2004 and 2007. GCC does not support the +uncorrected version. +</p> +<p>A fourth version of the C standard, known as <em>C11</em>, was published +in 2011 as ISO/IEC 9899:2011. (While in development, drafts of this +standard version were referred to as <em>C1X</em>.) +GCC has substantially complete support +for this standard, enabled with <samp>-std=c11</samp> or +<samp>-std=iso9899:2011</samp>. A version with corrections integrated was +prepared in 2017 and published in 2018 as ISO/IEC 9899:2018; it is +known as <em>C17</em> and is supported with <samp>-std=c17</samp> or +<samp>-std=iso9899:2017</samp>; the corrections are also applied with +<samp>-std=c11</samp>, and the only difference between the options is the +value of <code>__STDC_VERSION__</code>. +</p> +<p>A further version of the C standard, known as <em>C2X</em>, is under +development; experimental and incomplete support for this is enabled +with <samp>-std=c2x</samp>. +</p> +<p>By default, GCC provides some extensions to the C language that, on +rare occasions conflict with the C standard. See <a href="C-Extensions.html#C-Extensions">Extensions to the C Language Family</a>. +Some features that are part of the C99 standard +are accepted as extensions in C90 mode, and some features that are part +of the C11 standard are accepted as extensions in C90 and C99 modes. +Use of the +<samp>-std</samp> options listed above disables these extensions where +they conflict with the C standard version selected. You may also +select an extended version of the C language explicitly with +<samp>-std=gnu90</samp> (for C90 with GNU extensions), <samp>-std=gnu99</samp> +(for C99 with GNU extensions) or <samp>-std=gnu11</samp> (for C11 with GNU +extensions). +</p> +<p>The default, if no C language dialect options are given, +is <samp>-std=gnu17</samp>. +</p> +<p>The ISO C standard defines (in clause 4) two classes of conforming +implementation. A <em>conforming hosted implementation</em> supports the +whole standard including all the library facilities; a <em>conforming +freestanding implementation</em> is only required to provide certain +library facilities: those in <code><float.h></code>, <code><limits.h></code>, +<code><stdarg.h></code>, and <code><stddef.h></code>; since AMD1, also those in +<code><iso646.h></code>; since C99, also those in <code><stdbool.h></code> and +<code><stdint.h></code>; and since C11, also those in <code><stdalign.h></code> +and <code><stdnoreturn.h></code>. In addition, complex types, added in C99, are not +required for freestanding implementations. +</p> +<p>The standard also defines two environments for programs, a +<em>freestanding environment</em>, required of all implementations and +which may not have library facilities beyond those required of +freestanding implementations, where the handling of program startup +and termination are implementation-defined; and a <em>hosted +environment</em>, which is not required, in which all the library +facilities are provided and startup is through a function <code>int +main (void)</code> or <code>int main (int, char *[])</code>. An OS kernel is an example +of a program running in a freestanding environment; +a program using the facilities of an +operating system is an example of a program running in a hosted environment. +</p> +<a name="index-ffreestanding"></a> +<p>GCC aims towards being usable as a conforming freestanding +implementation, or as the compiler for a conforming hosted +implementation. By default, it acts as the compiler for a hosted +implementation, defining <code>__STDC_HOSTED__</code> as <code>1</code> and +presuming that when the names of ISO C functions are used, they have +the semantics defined in the standard. To make it act as a conforming +freestanding implementation for a freestanding environment, use the +option <samp>-ffreestanding</samp>; it then defines +<code>__STDC_HOSTED__</code> to <code>0</code> and does not make assumptions about the +meanings of function names from the standard library, with exceptions +noted below. To build an OS kernel, you may well still need to make +your own arrangements for linking and startup. +See <a href="C-Dialect-Options.html#C-Dialect-Options">Options Controlling C Dialect</a>. +</p> +<p>GCC does not provide the library facilities required only of hosted +implementations, nor yet all the facilities required by C99 of +freestanding implementations on all platforms. +To use the facilities of a hosted +environment, you need to find them elsewhere (for example, in the +GNU C library). See <a href="Standard-Libraries.html#Standard-Libraries">Standard Libraries</a>. +</p> +<p>Most of the compiler support routines used by GCC are present in +<samp>libgcc</samp>, but there are a few exceptions. GCC requires the +freestanding environment provide <code>memcpy</code>, <code>memmove</code>, +<code>memset</code> and <code>memcmp</code>. +Finally, if <code>__builtin_trap</code> is used, and the target does +not implement the <code>trap</code> pattern, then GCC emits a call +to <code>abort</code>. +</p> +<p>For references to Technical Corrigenda, Rationale documents and +information concerning the history of C that is available online, see +<a href="https://gcc.gnu.org/readings.html">https://gcc.gnu.org/readings.html</a> +</p> +<a name="C_002b_002b-Language"></a> +<h3 class="section">2.2 C++ Language</h3> + +<p>GCC supports the original ISO C++ standard published in 1998, +and the 2011, 2014, 2017 and mostly 2020 revisions. +</p> +<p>The original ISO C++ standard was published as the ISO standard (ISO/IEC +14882:1998) and amended by a Technical Corrigenda published in 2003 +(ISO/IEC 14882:2003). These standards are referred to as C++98 and +C++03, respectively. GCC implements the majority of C++98 (<code>export</code> +is a notable exception) and most of the changes in C++03. To select +this standard in GCC, use one of the options <samp>-ansi</samp>, +<samp>-std=c++98</samp>, or <samp>-std=c++03</samp>; to obtain all the diagnostics +required by the standard, you should also specify <samp>-pedantic</samp> (or +<samp>-pedantic-errors</samp> if you want them to be errors rather than +warnings). +</p> +<p>A revised ISO C++ standard was published in 2011 as ISO/IEC +14882:2011, and is referred to as C++11; before its publication it was +commonly referred to as C++0x. C++11 contains several changes to the +C++ language, all of which have been implemented in GCC. For details +see <a href="https://gcc.gnu.org/projects/cxx-status.html#cxx11">https://gcc.gnu.org/projects/cxx-status.html#cxx11</a>. +To select this standard in GCC, use the option <samp>-std=c++11</samp>. +</p> +<p>Another revised ISO C++ standard was published in 2014 as ISO/IEC +14882:2014, and is referred to as C++14; before its publication it was +sometimes referred to as C++1y. C++14 contains several further +changes to the C++ language, all of which have been implemented in GCC. +For details see <a href="https://gcc.gnu.org/projects/cxx-status.html#cxx14">https://gcc.gnu.org/projects/cxx-status.html#cxx14</a>. +To select this standard in GCC, use the option <samp>-std=c++14</samp>. +</p> +<p>The C++ language was further revised in 2017 and ISO/IEC 14882:2017 was +published. This is referred to as C++17, and before publication was +often referred to as C++1z. GCC supports all the changes in that +specification. For further details see +<a href="https://gcc.gnu.org/projects/cxx-status.html#cxx17">https://gcc.gnu.org/projects/cxx-status.html#cxx17</a>. Use the option +<samp>-std=c++17</samp> to select this variant of C++. +</p> +<p>Another revised ISO C++ standard was published in 2020 as ISO/IEC +14882:2020, and is referred to as C++20; before its publication it was +sometimes referred to as C++2a. GCC supports most of the changes in the +new specification. For further details see +<a href="https://gcc.gnu.org/projects/cxx-status.html#cxx20">https://gcc.gnu.org/projects/cxx-status.html#cxx20</a>. +To select this standard in GCC, use the option <samp>-std=c++20</samp>. +</p> +<p>More information about the C++ standards is available on the ISO C++ +committee’s web site at <a href="http://www.open-std.org/jtc1/sc22/wg21/">http://www.open-std.org/jtc1/sc22/wg21/</a>. +</p> +<p>To obtain all the diagnostics required by any of the standard versions +described above you should specify <samp>-pedantic</samp> +or <samp>-pedantic-errors</samp>, otherwise GCC will allow some non-ISO C++ +features as extensions. See <a href="Warning-Options.html#Warning-Options">Warning Options</a>. +</p> +<p>By default, GCC also provides some additional extensions to the C++ language +that on rare occasions conflict with the C++ standard. See <a href="C_002b_002b-Dialect-Options.html#C_002b_002b-Dialect-Options">Options Controlling C++ Dialect</a>. Use of the +<samp>-std</samp> options listed above disables these extensions where they +they conflict with the C++ standard version selected. You may also +select an extended version of the C++ language explicitly with +<samp>-std=gnu++98</samp> (for C++98 with GNU extensions), or +<samp>-std=gnu++11</samp> (for C++11 with GNU extensions), or +<samp>-std=gnu++14</samp> (for C++14 with GNU extensions), or +<samp>-std=gnu++17</samp> (for C++17 with GNU extensions), or +<samp>-std=gnu++20</samp> (for C++20 with GNU extensions). +</p> +<p>The default, if +no C++ language dialect options are given, is <samp>-std=gnu++17</samp>. +</p> +<a name="Objective_002dC-and-Objective_002dC_002b_002b-Languages"></a> +<h3 class="section">2.3 Objective-C and Objective-C++ Languages</h3> +<a name="index-Objective_002dC-1"></a> +<a name="index-Objective_002dC_002b_002b-1"></a> + +<p>GCC supports “traditional” Objective-C (also known as “Objective-C +1.0”) and contains support for the Objective-C exception and +synchronization syntax. It has also support for a number of +“Objective-C 2.0” language extensions, including properties, fast +enumeration (only for Objective-C), method attributes and the +@optional and @required keywords in protocols. GCC supports +Objective-C++ and features available in Objective-C are also available +in Objective-C++. +</p> +<p>GCC by default uses the GNU Objective-C runtime library, which is part +of GCC and is not the same as the Apple/NeXT Objective-C runtime +library used on Apple systems. There are a number of differences +documented in this manual. The options <samp>-fgnu-runtime</samp> and +<samp>-fnext-runtime</samp> allow you to switch between producing output +that works with the GNU Objective-C runtime library and output that +works with the Apple/NeXT Objective-C runtime library. +</p> +<p>There is no formal written standard for Objective-C or Objective-C++. +The authoritative manual on traditional Objective-C (1.0) is +“Object-Oriented Programming and the Objective-C Language”: +<a href="https://gnustep.github.io/resources/documentation/ObjectivCBook.pdf">https://gnustep.github.io/resources/documentation/ObjectivCBook.pdf</a> +is the original NeXTstep document. +</p> +<p>The Objective-C exception and synchronization syntax (that is, the +keywords <code>@try</code>, <code>@throw</code>, <code>@catch</code>, +<code>@finally</code> and <code>@synchronized</code>) is +supported by GCC and is enabled with the option +<samp>-fobjc-exceptions</samp>. The syntax is briefly documented in this +manual and in the Objective-C 2.0 manuals from Apple. +</p> +<p>The Objective-C 2.0 language extensions and features are automatically +enabled; they include properties (via the <code>@property</code>, +<code>@synthesize</code> and +<code>@dynamic keywords</code>), fast enumeration (not available in +Objective-C++), attributes for methods (such as <code>deprecated</code>, +<code>noreturn</code>, <code>sentinel</code>, <code>format</code>), +the <code>unused</code> attribute for method arguments, the +<code>@package</code> keyword for instance variables and the <code>@optional</code> and +<code>@required</code> keywords in protocols. You can disable all these +Objective-C 2.0 language extensions with the option +<samp>-fobjc-std=objc1</samp>, which causes the compiler to recognize the +same Objective-C language syntax recognized by GCC 4.0, and to produce +an error if one of the new features is used. +</p> +<p>GCC has currently no support for non-fragile instance variables. +</p> +<p>The authoritative manual on Objective-C 2.0 is available from Apple: +</p><ul> +<li> <a href="https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html">https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html</a> +</li></ul> + +<p>For more information concerning the history of Objective-C that is +available online, see <a href="https://gcc.gnu.org/readings.html">https://gcc.gnu.org/readings.html</a> +</p> +<a name="Go-Language"></a> +<h3 class="section">2.4 Go Language</h3> + +<p>As of the GCC 4.7.1 release, GCC supports the Go 1 language standard, +described at <a href="https://go.dev/doc/go1">https://go.dev/doc/go1</a>. +</p> +<a name="D-language"></a> +<h3 class="section">2.5 D language</h3> + +<p>GCC supports the D 2.0 programming language. The D language itself is +currently defined by its reference implementation and supporting language +specification, described at <a href="https://dlang.org/spec/spec.html">https://dlang.org/spec/spec.html</a>. +</p> +<a name="References-for-Other-Languages"></a> +<h3 class="section">2.6 References for Other Languages</h3> + +<p>See <a href="http://gcc.gnu.org/onlinedocs/gnat_rm/index.html#Top">About This Guide</a> in <cite>GNAT Reference Manual</cite>, for information on standard +conformance and compatibility of the Ada compiler. +</p> +<p>See <a href="http://gcc.gnu.org/onlinedocs/gfortran/Standards.html#Standards">Standards</a> in <cite>The GNU Fortran Compiler</cite>, for details +of standards supported by GNU Fortran. +</p> + +<hr> +<div class="header"> +<p> +Next: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="n" rel="next">Invoking GCC</a>, Previous: <a href="G_002b_002b-and-GCC.html#G_002b_002b-and-GCC" accesskey="p" rel="previous">G++ and GCC</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |