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diff --git a/share/doc/gcc/Compatibility.html b/share/doc/gcc/Compatibility.html new file mode 100644 index 0000000..4a2fc46 --- /dev/null +++ b/share/doc/gcc/Compatibility.html @@ -0,0 +1,238 @@ +<!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): Compatibility</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Compatibility"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Compatibility"> +<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="Gcov.html#Gcov" rel="next" title="Gcov"> +<link href="Forwarding-hook.html#Forwarding-hook" rel="previous" title="Forwarding hook"> +<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="Compatibility"></a> +<div class="header"> +<p> +Next: <a href="Gcov.html#Gcov" accesskey="n" rel="next">Gcov</a>, Previous: <a href="Objective_002dC.html#Objective_002dC" accesskey="p" rel="previous">Objective-C</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="Binary-Compatibility"></a> +<h2 class="chapter">9 Binary Compatibility</h2> +<a name="index-binary-compatibility"></a> +<a name="index-ABI"></a> +<a name="index-application-binary-interface"></a> + +<p>Binary compatibility encompasses several related concepts: +</p> +<dl compact="compact"> +<dt><em>application binary interface (ABI)</em></dt> +<dd><p>The set of runtime conventions followed by all of the tools that deal +with binary representations of a program, including compilers, assemblers, +linkers, and language runtime support. +Some ABIs are formal with a written specification, possibly designed +by multiple interested parties. Others are simply the way things are +actually done by a particular set of tools. +</p> +</dd> +<dt><em>ABI conformance</em></dt> +<dd><p>A compiler conforms to an ABI if it generates code that follows all of +the specifications enumerated by that ABI. +A library conforms to an ABI if it is implemented according to that ABI. +An application conforms to an ABI if it is built using tools that conform +to that ABI and does not contain source code that specifically changes +behavior specified by the ABI. +</p> +</dd> +<dt><em>calling conventions</em></dt> +<dd><p>Calling conventions are a subset of an ABI that specify of how arguments +are passed and function results are returned. +</p> +</dd> +<dt><em>interoperability</em></dt> +<dd><p>Different sets of tools are interoperable if they generate files that +can be used in the same program. The set of tools includes compilers, +assemblers, linkers, libraries, header files, startup files, and debuggers. +Binaries produced by different sets of tools are not interoperable unless +they implement the same ABI. This applies to different versions of the +same tools as well as tools from different vendors. +</p> +</dd> +<dt><em>intercallability</em></dt> +<dd><p>Whether a function in a binary built by one set of tools can call a +function in a binary built by a different set of tools is a subset +of interoperability. +</p> +</dd> +<dt><em>implementation-defined features</em></dt> +<dd><p>Language standards include lists of implementation-defined features whose +behavior can vary from one implementation to another. Some of these +features are normally covered by a platform’s ABI and others are not. +The features that are not covered by an ABI generally affect how a +program behaves, but not intercallability. +</p> +</dd> +<dt><em>compatibility</em></dt> +<dd><p>Conformance to the same ABI and the same behavior of implementation-defined +features are both relevant for compatibility. +</p></dd> +</dl> + +<p>The application binary interface implemented by a C or C++ compiler +affects code generation and runtime support for: +</p> +<ul> +<li> size and alignment of data types +</li><li> layout of structured types +</li><li> calling conventions +</li><li> register usage conventions +</li><li> interfaces for runtime arithmetic support +</li><li> object file formats +</li></ul> + +<p>In addition, the application binary interface implemented by a C++ compiler +affects code generation and runtime support for: +</p><ul> +<li> name mangling +</li><li> exception handling +</li><li> invoking constructors and destructors +</li><li> layout, alignment, and padding of classes +</li><li> layout and alignment of virtual tables +</li></ul> + +<p>Some GCC compilation options cause the compiler to generate code that +does not conform to the platform’s default ABI. Other options cause +different program behavior for implementation-defined features that are +not covered by an ABI. These options are provided for consistency with +other compilers that do not follow the platform’s default ABI or the +usual behavior of implementation-defined features for the platform. +Be very careful about using such options. +</p> +<p>Most platforms have a well-defined ABI that covers C code, but ABIs +that cover C++ functionality are not yet common. +</p> +<p>Starting with GCC 3.2, GCC binary conventions for C++ are based on a +written, vendor-neutral C++ ABI that was designed to be specific to +64-bit Itanium but also includes generic specifications that apply to +any platform. +This C++ ABI is also implemented by other compiler vendors on some +platforms, notably GNU/Linux and BSD systems. +We have tried hard to provide a stable ABI that will be compatible with +future GCC releases, but it is possible that we will encounter problems +that make this difficult. Such problems could include different +interpretations of the C++ ABI by different vendors, bugs in the ABI, or +bugs in the implementation of the ABI in different compilers. +GCC’s <samp>-Wabi</samp> switch warns when G++ generates code that is +probably not compatible with the C++ ABI. +</p> +<p>The C++ library used with a C++ compiler includes the Standard C++ +Library, with functionality defined in the C++ Standard, plus language +runtime support. The runtime support is included in a C++ ABI, but there +is no formal ABI for the Standard C++ Library. Two implementations +of that library are interoperable if one follows the de-facto ABI of the +other and if they are both built with the same compiler, or with compilers +that conform to the same ABI for C++ compiler and runtime support. +</p> +<p>When G++ and another C++ compiler conform to the same C++ ABI, but the +implementations of the Standard C++ Library that they normally use do not +follow the same ABI for the Standard C++ Library, object files built with +those compilers can be used in the same program only if they use the same +C++ library. This requires specifying the location of the C++ library +header files when invoking the compiler whose usual library is not being +used. The location of GCC’s C++ header files depends on how the GCC +build was configured, but can be seen by using the G++ <samp>-v</samp> option. +With default configuration options for G++ 3.3 the compile line for a +different C++ compiler needs to include +</p> +<div class="smallexample"> +<pre class="smallexample"> -I<var>gcc_install_directory</var>/include/c++/3.3 +</pre></div> + +<p>Similarly, compiling code with G++ that must use a C++ library other +than the GNU C++ library requires specifying the location of the header +files for that other library. +</p> +<p>The most straightforward way to link a program to use a particular +C++ library is to use a C++ driver that specifies that C++ library by +default. The <code>g++</code> driver, for example, tells the linker where +to find GCC’s C++ library (<samp>libstdc++</samp>) plus the other libraries +and startup files it needs, in the proper order. +</p> +<p>If a program must use a different C++ library and it’s not possible +to do the final link using a C++ driver that uses that library by default, +it is necessary to tell <code>g++</code> the location and name of that +library. It might also be necessary to specify different startup files +and other runtime support libraries, and to suppress the use of GCC’s +support libraries with one or more of the options <samp>-nostdlib</samp>, +<samp>-nostartfiles</samp>, and <samp>-nodefaultlibs</samp>. +</p> + +<hr> +<div class="header"> +<p> +Next: <a href="Gcov.html#Gcov" accesskey="n" rel="next">Gcov</a>, Previous: <a href="Objective_002dC.html#Objective_002dC" accesskey="p" rel="previous">Objective-C</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> |