| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- This file documents the GNU linker LD |
| (Linaro GDB 2015.08) |
| version 2.25.51. |
| |
| Copyright (C) 1991-2015 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 no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled "GNU Free Documentation License". --> |
| <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>LD: PROVIDE</title> |
| |
| <meta name="description" content="LD: PROVIDE"> |
| <meta name="keywords" content="LD: PROVIDE"> |
| <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="LD-Index.html#LD-Index" rel="index" title="LD Index"> |
| <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> |
| <link href="Assignments.html#Assignments" rel="up" title="Assignments"> |
| <link href="PROVIDE_005fHIDDEN.html#PROVIDE_005fHIDDEN" rel="next" title="PROVIDE_HIDDEN"> |
| <link href="HIDDEN.html#HIDDEN" rel="prev" title="HIDDEN"> |
| <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="PROVIDE"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="PROVIDE_005fHIDDEN.html#PROVIDE_005fHIDDEN" accesskey="n" rel="next">PROVIDE_HIDDEN</a>, Previous: <a href="HIDDEN.html#HIDDEN" accesskey="p" rel="prev">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> |
| </div> |
| <hr> |
| <a name="PROVIDE-1"></a> |
| <h4 class="subsection">3.5.3 PROVIDE</h4> |
| <a name="index-PROVIDE"></a> |
| <p>In some cases, it is desirable for a linker script to define a symbol |
| only if it is referenced and is not defined by any object included in |
| the link. For example, traditional linkers defined the symbol |
| ‘<samp>etext</samp>’. However, ANSI C requires that the user be able to use |
| ‘<samp>etext</samp>’ as a function name without encountering an error. The |
| <code>PROVIDE</code> keyword may be used to define a symbol, such as |
| ‘<samp>etext</samp>’, only if it is referenced but not defined. The syntax is |
| <code>PROVIDE(<var>symbol</var> = <var>expression</var>)</code>. |
| </p> |
| <p>Here is an example of using <code>PROVIDE</code> to define ‘<samp>etext</samp>’: |
| </p><div class="smallexample"> |
| <pre class="smallexample">SECTIONS |
| { |
| .text : |
| { |
| *(.text) |
| _etext = .; |
| PROVIDE(etext = .); |
| } |
| } |
| </pre></div> |
| |
| <p>In this example, if the program defines ‘<samp>_etext</samp>’ (with a leading |
| underscore), the linker will give a multiple definition error. If, on |
| the other hand, the program defines ‘<samp>etext</samp>’ (with no leading |
| underscore), the linker will silently use the definition in the program. |
| If the program references ‘<samp>etext</samp>’ but does not define it, the |
| linker will use the definition in the linker script. |
| </p> |
| |
| |
| |
| </body> |
| </html> |
