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diff --git a/share/doc/gccint/Blocks.html b/share/doc/gccint/Blocks.html new file mode 100644 index 0000000..7995058 --- /dev/null +++ b/share/doc/gccint/Blocks.html @@ -0,0 +1,116 @@ +<!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: Blocks</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Blocks"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Blocks"> +<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="Statements.html#Statements" rel="up" title="Statements"> +<link href="Statement-Sequences.html#Statement-Sequences" rel="next" title="Statement Sequences"> +<link href="Basic-Statements.html#Basic-Statements" rel="previous" title="Basic Statements"> +<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="Blocks"></a> +<div class="header"> +<p> +Next: <a href="Statement-Sequences.html#Statement-Sequences" accesskey="n" rel="next">Statement Sequences</a>, Previous: <a href="Basic-Statements.html#Basic-Statements" accesskey="p" rel="previous">Basic Statements</a>, Up: <a href="Statements.html#Statements" accesskey="u" rel="up">Statements</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="Blocks-1"></a> +<h4 class="subsection">11.7.2 Blocks</h4> +<a name="index-Blocks"></a> + +<p>Block scopes and the variables they declare in GENERIC are +expressed using the <code>BIND_EXPR</code> code, which in previous +versions of GCC was primarily used for the C statement-expression +extension. +</p> +<p>Variables in a block are collected into <code>BIND_EXPR_VARS</code> in +declaration order through their <code>TREE_CHAIN</code> field. Any runtime +initialization is moved out of <code>DECL_INITIAL</code> and into a +statement in the controlled block. When gimplifying from C or C++, +this initialization replaces the <code>DECL_STMT</code>. These variables +will never require cleanups. The scope of these variables is just the +body +</p> +<p>Variable-length arrays (VLAs) complicate this process, as their size +often refers to variables initialized earlier in the block and their +initialization involves an explicit stack allocation. To handle this, +we add an indirection and replace them with a pointer to stack space +allocated by means of <code>alloca</code>. In most cases, we also arrange +for this space to be reclaimed when the enclosing <code>BIND_EXPR</code> is +exited, the exception to this being when there is an explicit call to +<code>alloca</code> in the source code, in which case the stack is left +depressed on exit of the <code>BIND_EXPR</code>. +</p> +<p>A C++ program will usually contain more <code>BIND_EXPR</code>s than +there are syntactic blocks in the source code, since several C++ +constructs have implicit scopes associated with them. On the +other hand, although the C++ front end uses pseudo-scopes to +handle cleanups for objects with destructors, these don’t +translate into the GIMPLE form; multiple declarations at the same +level use the same <code>BIND_EXPR</code>. +</p> + + + +</body> +</html> |