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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 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gccint/Uninitialized-Data.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
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diff --git a/share/doc/gccint/Uninitialized-Data.html b/share/doc/gccint/Uninitialized-Data.html new file mode 100644 index 0000000..cdaaad9 --- /dev/null +++ b/share/doc/gccint/Uninitialized-Data.html @@ -0,0 +1,192 @@ +<!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: Uninitialized Data</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Uninitialized Data"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Uninitialized Data"> +<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="Assembler-Format.html#Assembler-Format" rel="up" title="Assembler Format"> +<link href="Label-Output.html#Label-Output" rel="next" title="Label Output"> +<link href="Data-Output.html#Data-Output" rel="previous" title="Data Output"> +<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="Uninitialized-Data"></a> +<div class="header"> +<p> +Next: <a href="Label-Output.html#Label-Output" accesskey="n" rel="next">Label Output</a>, Previous: <a href="Data-Output.html#Data-Output" accesskey="p" rel="previous">Data Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</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="Output-of-Uninitialized-Variables"></a> +<h4 class="subsection">18.20.3 Output of Uninitialized Variables</h4> + +<p>Each of the macros in this section is used to do the whole job of +outputting a single uninitialized variable. +</p> +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fCOMMON"></a>Macro: <strong>ASM_OUTPUT_COMMON</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>rounded</var>)</em></dt> +<dd><p>A C statement (sans semicolon) to output to the stdio stream +<var>stream</var> the assembler definition of a common-label named +<var>name</var> whose size is <var>size</var> bytes. The variable <var>rounded</var> +is the size rounded up to whatever alignment the caller wants. It is +possible that <var>size</var> may be zero, for instance if a struct with no +other member than a zero-length array is defined. In this case, the +backend must output a symbol definition that allocates at least one +byte, both so that the address of the resulting object does not compare +equal to any other, and because some object formats cannot even express +the concept of a zero-sized common symbol, as that is how they represent +an ordinary undefined external. +</p> +<p>Use the expression <code>assemble_name (<var>stream</var>, <var>name</var>)</code> to +output the name itself; before and after that, output the additional +assembler syntax for defining the name, and a newline. +</p> +<p>This macro controls how the assembler definitions of uninitialized +common global variables are output. +</p></dd></dl> + +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fCOMMON"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_COMMON</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> +<dd><p>Like <code>ASM_OUTPUT_COMMON</code> except takes the required alignment as a +separate, explicit argument. If you define this macro, it is used in +place of <code>ASM_OUTPUT_COMMON</code>, and gives you more flexibility in +handling the required alignment of the variable. The alignment is specified +as the number of bits. +</p></dd></dl> + +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fDECL_005fCOMMON"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_DECL_COMMON</strong> <em>(<var>stream</var>, <var>decl</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> +<dd><p>Like <code>ASM_OUTPUT_ALIGNED_COMMON</code> except that <var>decl</var> of the +variable to be output, if there is one, or <code>NULL_TREE</code> if there +is no corresponding variable. If you define this macro, GCC will use it +in place of both <code>ASM_OUTPUT_COMMON</code> and +<code>ASM_OUTPUT_ALIGNED_COMMON</code>. Define this macro when you need to see +the variable’s decl in order to chose what to output. +</p></dd></dl> + +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fBSS"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_BSS</strong> <em>(<var>stream</var>, <var>decl</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> +<dd><p>A C statement (sans semicolon) to output to the stdio stream +<var>stream</var> the assembler definition of uninitialized global <var>decl</var> named +<var>name</var> whose size is <var>size</var> bytes. The variable <var>alignment</var> +is the alignment specified as the number of bits. +</p> +<p>Try to use function <code>asm_output_aligned_bss</code> defined in file +<samp>varasm.cc</samp> when defining this macro. If unable, use the expression +<code>assemble_name (<var>stream</var>, <var>name</var>)</code> to output the name itself; +before and after that, output the additional assembler syntax for defining +the name, and a newline. +</p> +<p>There are two ways of handling global BSS. One is to define this macro. +The other is to have <code>TARGET_ASM_SELECT_SECTION</code> return a +switchable BSS section (see <a href="File-Framework.html#TARGET_005fHAVE_005fSWITCHABLE_005fBSS_005fSECTIONS">TARGET_HAVE_SWITCHABLE_BSS_SECTIONS</a>). +You do not need to do both. +</p> +<p>Some languages do not have <code>common</code> data, and require a +non-common form of global BSS in order to handle uninitialized globals +efficiently. C++ is one example of this. However, if the target does +not support global BSS, the front end may choose to make globals +common in order to save space in the object file. +</p></dd></dl> + +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fLOCAL"></a>Macro: <strong>ASM_OUTPUT_LOCAL</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>rounded</var>)</em></dt> +<dd><p>A C statement (sans semicolon) to output to the stdio stream +<var>stream</var> the assembler definition of a local-common-label named +<var>name</var> whose size is <var>size</var> bytes. The variable <var>rounded</var> +is the size rounded up to whatever alignment the caller wants. +</p> +<p>Use the expression <code>assemble_name (<var>stream</var>, <var>name</var>)</code> to +output the name itself; before and after that, output the additional +assembler syntax for defining the name, and a newline. +</p> +<p>This macro controls how the assembler definitions of uninitialized +static variables are output. +</p></dd></dl> + +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fLOCAL"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_LOCAL</strong> <em>(<var>stream</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> +<dd><p>Like <code>ASM_OUTPUT_LOCAL</code> except takes the required alignment as a +separate, explicit argument. If you define this macro, it is used in +place of <code>ASM_OUTPUT_LOCAL</code>, and gives you more flexibility in +handling the required alignment of the variable. The alignment is specified +as the number of bits. +</p></dd></dl> + +<dl> +<dt><a name="index-ASM_005fOUTPUT_005fALIGNED_005fDECL_005fLOCAL"></a>Macro: <strong>ASM_OUTPUT_ALIGNED_DECL_LOCAL</strong> <em>(<var>stream</var>, <var>decl</var>, <var>name</var>, <var>size</var>, <var>alignment</var>)</em></dt> +<dd><p>Like <code>ASM_OUTPUT_ALIGNED_LOCAL</code> except that <var>decl</var> of the +variable to be output, if there is one, or <code>NULL_TREE</code> if there +is no corresponding variable. If you define this macro, GCC will use it +in place of both <code>ASM_OUTPUT_LOCAL</code> and +<code>ASM_OUTPUT_ALIGNED_LOCAL</code>. Define this macro when you need to see +the variable’s decl in order to chose what to output. +</p></dd></dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Label-Output.html#Label-Output" accesskey="n" rel="next">Label Output</a>, Previous: <a href="Data-Output.html#Data-Output" accesskey="p" rel="previous">Data Output</a>, Up: <a href="Assembler-Format.html#Assembler-Format" accesskey="u" rel="up">Assembler Format</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> |