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| <title>LD: Simple Assignments</title> |
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| Next: <a href="HIDDEN.html#HIDDEN" accesskey="n" rel="next">HIDDEN</a>, Up: <a href="Assignments.html#Assignments" accesskey="u" rel="up">Assignments</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Simple-Assignments-1"></a> |
| <h4 class="subsection">3.5.1 Simple Assignments</h4> |
| |
| <p>You may assign to a symbol using any of the C assignment operators: |
| </p> |
| <dl compact="compact"> |
| <dt><code><var>symbol</var> = <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> += <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> -= <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> *= <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> /= <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> <<= <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> >>= <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> &= <var>expression</var> ;</code></dt> |
| <dt><code><var>symbol</var> |= <var>expression</var> ;</code></dt> |
| </dl> |
| |
| <p>The first case will define <var>symbol</var> to the value of |
| <var>expression</var>. In the other cases, <var>symbol</var> must already be |
| defined, and the value will be adjusted accordingly. |
| </p> |
| <p>The special symbol name ‘<samp>.</samp>’ indicates the location counter. You |
| may only use this within a <code>SECTIONS</code> command. See <a href="Location-Counter.html#Location-Counter">Location Counter</a>. |
| </p> |
| <p>The semicolon after <var>expression</var> is required. |
| </p> |
| <p>Expressions are defined below; see <a href="Expressions.html#Expressions">Expressions</a>. |
| </p> |
| <p>You may write symbol assignments as commands in their own right, or as |
| statements within a <code>SECTIONS</code> command, or as part of an output |
| section description in a <code>SECTIONS</code> command. |
| </p> |
| <p>The section of the symbol will be set from the section of the |
| expression; for more information, see <a href="Expression-Section.html#Expression-Section">Expression Section</a>. |
| </p> |
| <p>Here is an example showing the three different places that symbol |
| assignments may be used: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">floating_point = 0; |
| SECTIONS |
| { |
| .text : |
| { |
| *(.text) |
| _etext = .; |
| } |
| _bdata = (. + 3) & ~ 3; |
| .data : { *(.data) } |
| } |
| </pre></div> |
| <p>In this example, the symbol ‘<samp>floating_point</samp>’ will be defined as |
| zero. The symbol ‘<samp>_etext</samp>’ will be defined as the address following |
| the last ‘<samp>.text</samp>’ input section. The symbol ‘<samp>_bdata</samp>’ will be |
| defined as the address following the ‘<samp>.text</samp>’ output section aligned |
| upward to a 4 byte boundary. |
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