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diff --git a/share/doc/gccint/Interface.html b/share/doc/gccint/Interface.html new file mode 100644 index 0000000..43c58d2 --- /dev/null +++ b/share/doc/gccint/Interface.html @@ -0,0 +1,153 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- 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>GNU Compiler Collection (GCC) Internals: Interface</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Interface"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Interface"> +<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="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="index.html#Top" rel="up" title="Top"> +<link href="Libgcc.html#Libgcc" rel="next" title="Libgcc"> +<link href="Portability.html#Portability" rel="previous" title="Portability"> +<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="Interface"></a> +<div class="header"> +<p> +Next: <a href="Libgcc.html#Libgcc" accesskey="n" rel="next">Libgcc</a>, Previous: <a href="Portability.html#Portability" accesskey="p" rel="previous">Portability</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="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Interfacing-to-GCC-Output"></a> +<h2 class="chapter">3 Interfacing to GCC Output</h2> +<a name="index-interfacing-to-GCC-output"></a> +<a name="index-run_002dtime-conventions"></a> +<a name="index-function-call-conventions"></a> +<a name="index-conventions_002c-run_002dtime"></a> + +<p>GCC is normally configured to use the same function calling convention +normally in use on the target system. This is done with the +machine-description macros described (see <a href="Target-Macros.html#Target-Macros">Target Macros</a>). +</p> +<a name="index-unions_002c-returning"></a> +<a name="index-structures_002c-returning"></a> +<a name="index-returning-structures-and-unions"></a> +<p>However, returning of structure and union values is done differently on +some target machines. As a result, functions compiled with PCC +returning such types cannot be called from code compiled with GCC, +and vice versa. This does not cause trouble often because few Unix +library routines return structures or unions. +</p> +<p>GCC code returns structures and unions that are 1, 2, 4 or 8 bytes +long in the same registers used for <code>int</code> or <code>double</code> return +values. (GCC typically allocates variables of such types in +registers also.) Structures and unions of other sizes are returned by +storing them into an address passed by the caller (usually in a +register). The target hook <code>TARGET_STRUCT_VALUE_RTX</code> +tells GCC where to pass this address. +</p> +<p>By contrast, PCC on most target machines returns structures and unions +of any size by copying the data into an area of static storage, and then +returning the address of that storage as if it were a pointer value. +The caller must copy the data from that memory area to the place where +the value is wanted. This is slower than the method used by GCC, and +fails to be reentrant. +</p> +<p>On some target machines, such as RISC machines and the 80386, the +standard system convention is to pass to the subroutine the address of +where to return the value. On these machines, GCC has been +configured to be compatible with the standard compiler, when this method +is used. It may not be compatible for structures of 1, 2, 4 or 8 bytes. +</p> +<a name="index-argument-passing"></a> +<a name="index-passing-arguments"></a> +<p>GCC uses the system’s standard convention for passing arguments. On +some machines, the first few arguments are passed in registers; in +others, all are passed on the stack. It would be possible to use +registers for argument passing on any machine, and this would probably +result in a significant speedup. But the result would be complete +incompatibility with code that follows the standard convention. So this +change is practical only if you are switching to GCC as the sole C +compiler for the system. We may implement register argument passing on +certain machines once we have a complete GNU system so that we can +compile the libraries with GCC. +</p> +<p>On some machines (particularly the SPARC), certain types of arguments +are passed “by invisible reference”. This means that the value is +stored in memory, and the address of the memory location is passed to +the subroutine. +</p> +<a name="index-longjmp-and-automatic-variables"></a> +<p>If you use <code>longjmp</code>, beware of automatic variables. ISO C says that +automatic variables that are not declared <code>volatile</code> have undefined +values after a <code>longjmp</code>. And this is all GCC promises to do, +because it is very difficult to restore register variables correctly, and +one of GCC’s features is that it can put variables in registers without +your asking it to. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Libgcc.html#Libgcc" accesskey="n" rel="next">Libgcc</a>, Previous: <a href="Portability.html#Portability" accesskey="p" rel="previous">Portability</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="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |