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diff --git a/share/doc/gcc/Constructing-Calls.html b/share/doc/gcc/Constructing-Calls.html new file mode 100644 index 0000000..2fb4918 --- /dev/null +++ b/share/doc/gcc/Constructing-Calls.html @@ -0,0 +1,210 @@ +<!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): Constructing Calls</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Constructing Calls"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Constructing Calls"> +<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="C-Extensions.html#C-Extensions" rel="up" title="C Extensions"> +<link href="Typeof.html#Typeof" rel="next" title="Typeof"> +<link href="Nonlocal-Gotos.html#Nonlocal-Gotos" rel="previous" title="Nonlocal Gotos"> +<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="Constructing-Calls"></a> +<div class="header"> +<p> +Next: <a href="Typeof.html#Typeof" accesskey="n" rel="next">Typeof</a>, Previous: <a href="Nonlocal-Gotos.html#Nonlocal-Gotos" accesskey="p" rel="previous">Nonlocal Gotos</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</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="Constructing-Function-Calls"></a> +<h3 class="section">6.6 Constructing Function Calls</h3> +<a name="index-constructing-calls"></a> +<a name="index-forwarding-calls"></a> + +<p>Using the built-in functions described below, you can record +the arguments a function received, and call another function +with the same arguments, without knowing the number or types +of the arguments. +</p> +<p>You can also record the return value of that function call, +and later return that value, without knowing what data type +the function tried to return (as long as your caller expects +that data type). +</p> +<p>However, these built-in functions may interact badly with some +sophisticated features or other extensions of the language. It +is, therefore, not recommended to use them outside very simple +functions acting as mere forwarders for their arguments. +</p> +<dl> +<dt><a name="index-_005f_005fbuiltin_005fapply_005fargs"></a>Built-in Function: <em>void *</em> <strong>__builtin_apply_args</strong> <em>()</em></dt> +<dd><p>This built-in function returns a pointer to data +describing how to perform a call with the same arguments as are passed +to the current function. +</p> +<p>The function saves the arg pointer register, structure value address, +and all registers that might be used to pass arguments to a function +into a block of memory allocated on the stack. Then it returns the +address of that block. +</p></dd></dl> + +<dl> +<dt><a name="index-_005f_005fbuiltin_005fapply"></a>Built-in Function: <em>void *</em> <strong>__builtin_apply</strong> <em>(void (*<var>function</var>)(), void *<var>arguments</var>, size_t <var>size</var>)</em></dt> +<dd><p>This built-in function invokes <var>function</var> +with a copy of the parameters described by <var>arguments</var> +and <var>size</var>. +</p> +<p>The value of <var>arguments</var> should be the value returned by +<code>__builtin_apply_args</code>. The argument <var>size</var> specifies the size +of the stack argument data, in bytes. +</p> +<p>This function returns a pointer to data describing +how to return whatever value is returned by <var>function</var>. The data +is saved in a block of memory allocated on the stack. +</p> +<p>It is not always simple to compute the proper value for <var>size</var>. The +value is used by <code>__builtin_apply</code> to compute the amount of data +that should be pushed on the stack and copied from the incoming argument +area. +</p></dd></dl> + +<dl> +<dt><a name="index-_005f_005fbuiltin_005freturn"></a>Built-in Function: <em>void</em> <strong>__builtin_return</strong> <em>(void *<var>result</var>)</em></dt> +<dd><p>This built-in function returns the value described by <var>result</var> from +the containing function. You should specify, for <var>result</var>, a value +returned by <code>__builtin_apply</code>. +</p></dd></dl> + +<dl> +<dt><a name="index-_005f_005fbuiltin_005fva_005farg_005fpack"></a>Built-in Function: <em></em> <strong>__builtin_va_arg_pack</strong> <em>()</em></dt> +<dd><p>This built-in function represents all anonymous arguments of an inline +function. It can be used only in inline functions that are always +inlined, never compiled as a separate function, such as those using +<code>__attribute__ ((__always_inline__))</code> or +<code>__attribute__ ((__gnu_inline__))</code> extern inline functions. +It must be only passed as last argument to some other function +with variable arguments. This is useful for writing small wrapper +inlines for variable argument functions, when using preprocessor +macros is undesirable. For example: +</p><div class="smallexample"> +<pre class="smallexample">extern int myprintf (FILE *f, const char *format, ...); +extern inline __attribute__ ((__gnu_inline__)) int +myprintf (FILE *f, const char *format, ...) +{ + int r = fprintf (f, "myprintf: "); + if (r < 0) + return r; + int s = fprintf (f, format, __builtin_va_arg_pack ()); + if (s < 0) + return s; + return r + s; +} +</pre></div> +</dd></dl> + +<dl> +<dt><a name="index-_005f_005fbuiltin_005fva_005farg_005fpack_005flen"></a>Built-in Function: <em>int</em> <strong>__builtin_va_arg_pack_len</strong> <em>()</em></dt> +<dd><p>This built-in function returns the number of anonymous arguments of +an inline function. It can be used only in inline functions that +are always inlined, never compiled as a separate function, such +as those using <code>__attribute__ ((__always_inline__))</code> or +<code>__attribute__ ((__gnu_inline__))</code> extern inline functions. +For example following does link- or run-time checking of open +arguments for optimized code: +</p><div class="smallexample"> +<pre class="smallexample">#ifdef __OPTIMIZE__ +extern inline __attribute__((__gnu_inline__)) int +myopen (const char *path, int oflag, ...) +{ + if (__builtin_va_arg_pack_len () > 1) + warn_open_too_many_arguments (); + + if (__builtin_constant_p (oflag)) + { + if ((oflag & O_CREAT) != 0 && __builtin_va_arg_pack_len () < 1) + { + warn_open_missing_mode (); + return __open_2 (path, oflag); + } + return open (path, oflag, __builtin_va_arg_pack ()); + } + + if (__builtin_va_arg_pack_len () < 1) + return __open_2 (path, oflag); + + return open (path, oflag, __builtin_va_arg_pack ()); +} +#endif +</pre></div> +</dd></dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Typeof.html#Typeof" accesskey="n" rel="next">Typeof</a>, Previous: <a href="Nonlocal-Gotos.html#Nonlocal-Gotos" accesskey="p" rel="previous">Nonlocal Gotos</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</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> |