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 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
 <a name="Ld-Sections"></a>
 <div class="header">
 <p>
 Next: <a href="As-Sections.html#As-Sections" accesskey="n" rel="next">As Sections</a>, Previous: <a href="Secs-Background.html#Secs-Background" accesskey="p" rel="prev">Secs Background</a>, Up: <a href="Sections.html#Sections" accesskey="u" rel="up">Sections</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Linker-Sections"></a>
 <h3 class="section">4.2 Linker Sections</h3>
 <p><code>ld</code> deals with just four kinds of sections, summarized below.
 </p>
 <dl compact="compact">
 <dd>
 <a name="index-named-sections"></a>
 <a name="index-sections_002c-named"></a>
 </dd>
 <dt><strong>named sections</strong></dt>
 <dd><a name="index-text-section"></a>
 <a name="index-data-section"></a>
 </dd>
 <dt><strong>text section</strong></dt>
 <dt><strong>data section</strong></dt>
 <dd><p>These sections hold your program.  <code>as</code> and <code>ld</code> treat them as
 separate but equal sections.  Anything you can say of one section is
 true of another.
 When the program is running, however, it is
 customary for the text section to be unalterable.  The
 text section is often shared among processes: it contains
 instructions, constants and the like.  The data section of a running
 program is usually alterable: for example, C variables would be stored
 in the data section.
 </p>
 <a name="index-bss-section"></a>
 </dd>
 <dt><strong>bss section</strong></dt>
 <dd><p>This section contains zeroed bytes when your program begins running.  It
 is used to hold uninitialized variables or common storage.  The length of
 each partial program&rsquo;s bss section is important, but because it starts
 out containing zeroed bytes there is no need to store explicit zero
 bytes in the object file.  The bss section was invented to eliminate
 those explicit zeros from object files.
 </p>
 <a name="index-absolute-section"></a>
 </dd>
 <dt><strong>absolute section</strong></dt>
 <dd><p>Address 0 of this section is always &ldquo;relocated&rdquo; to runtime address 0.
 This is useful if you want to refer to an address that <code>ld</code> must
 not change when relocating.  In this sense we speak of absolute
 addresses being &ldquo;unrelocatable&rdquo;: they do not change during relocation.
 </p>
 <a name="index-undefined-section"></a>
 </dd>
 <dt><strong>undefined section</strong></dt>
 <dd><p>This &ldquo;section&rdquo; is a catch-all for address references to objects not in
 the preceding sections.
 </p></dd>
 </dl>

 <a name="index-relocation-example"></a>
 <p>An idealized example of three relocatable sections follows.
 The example uses the traditional section names &lsquo;<samp>.text</samp>&rsquo; and &lsquo;<samp>.data</samp>&rsquo;.
 Memory addresses are on the horizontal axis.
 </p>
 <div class="smallexample">
 <pre class="smallexample">                      +-----+----+--+
 partial program # 1:  |ttttt|dddd|00|
                       +-----+----+--+

                       text   data bss
                       seg.   seg. seg.

                       +---+---+---+
 partial program # 2:  |TTT|DDD|000|
                       +---+---+---+

                       +--+---+-----+--+----+---+-----+~~
 linked program:       |  |TTT|ttttt|  |dddd|DDD|00000|
                       +--+---+-----+--+----+---+-----+~~

     addresses:        0 &hellip;
 </pre></div>

 <hr>
 <div class="header">
 <p>
 Next: <a href="As-Sections.html#As-Sections" accesskey="n" rel="next">As Sections</a>, Previous: <a href="Secs-Background.html#Secs-Background" accesskey="p" rel="prev">Secs Background</a>, Up: <a href="Sections.html#Sections" accesskey="u" rel="up">Sections</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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	<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
	<a name="Ld-Sections"></a>
	<div class="header">
	<p>
	Next: <a href="As-Sections.html#As-Sections" accesskey="n" rel="next">As Sections</a>, Previous: <a href="Secs-Background.html#Secs-Background" accesskey="p" rel="prev">Secs Background</a>, Up: <a href="Sections.html#Sections" accesskey="u" rel="up">Sections</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Linker-Sections"></a>
	<h3 class="section">4.2 Linker Sections</h3>
	<p><code>ld</code> deals with just four kinds of sections, summarized below.
	</p>
	<dl compact="compact">
	<dd>
	<a name="index-named-sections"></a>
	<a name="index-sections_002c-named"></a>
	</dd>
	<dt><strong>named sections</strong></dt>
	<dd><a name="index-text-section"></a>
	<a name="index-data-section"></a>
	</dd>
	<dt><strong>text section</strong></dt>
	<dt><strong>data section</strong></dt>
	<dd><p>These sections hold your program. <code>as</code> and <code>ld</code> treat them as
	separate but equal sections. Anything you can say of one section is
	true of another.
	When the program is running, however, it is
	customary for the text section to be unalterable. The
	text section is often shared among processes: it contains
	instructions, constants and the like. The data section of a running
	program is usually alterable: for example, C variables would be stored
	in the data section.
	</p>
	<a name="index-bss-section"></a>
	</dd>
	<dt><strong>bss section</strong></dt>
	<dd><p>This section contains zeroed bytes when your program begins running. It
	is used to hold uninitialized variables or common storage. The length of
	each partial program’s bss section is important, but because it starts
	out containing zeroed bytes there is no need to store explicit zero
	bytes in the object file. The bss section was invented to eliminate
	those explicit zeros from object files.
	</p>
	<a name="index-absolute-section"></a>
	</dd>
	<dt><strong>absolute section</strong></dt>
	<dd><p>Address 0 of this section is always “relocated” to runtime address 0.
	This is useful if you want to refer to an address that <code>ld</code> must
	not change when relocating. In this sense we speak of absolute
	addresses being “unrelocatable”: they do not change during relocation.
	</p>
	<a name="index-undefined-section"></a>
	</dd>
	<dt><strong>undefined section</strong></dt>
	<dd><p>This “section” is a catch-all for address references to objects not in
	the preceding sections.
	</p></dd>
	</dl>

	<a name="index-relocation-example"></a>
	<p>An idealized example of three relocatable sections follows.
	The example uses the traditional section names ‘<samp>.text</samp>’ and ‘<samp>.data</samp>’.
	Memory addresses are on the horizontal axis.
	</p>
	<div class="smallexample">
	<pre class="smallexample"> +-----+----+--+
	partial program # 1: \|ttttt\|dddd\|00\|
	+-----+----+--+

	text data bss
	seg. seg. seg.

	+---+---+---+
	partial program # 2: \|TTT\|DDD\|000\|
	+---+---+---+

	+--+---+-----+--+----+---+-----+~~
	linked program: \| \|TTT\|ttttt\| \|dddd\|DDD\|00000\|
	+--+---+-----+--+----+---+-----+~~

	addresses: 0 …
	</pre></div>

	<hr>
	<div class="header">
	<p>
	Next: <a href="As-Sections.html#As-Sections" accesskey="n" rel="next">As Sections</a>, Previous: <a href="Secs-Background.html#Secs-Background" accesskey="p" rel="prev">Secs Background</a>, Up: <a href="Sections.html#Sections" accesskey="u" rel="up">Sections</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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