<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- Copyright (C) 1988-2019 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 "Free Software" and "Free Software Needs Free Documentation", with the Front-Cover Texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. (a) The FSF's Back-Cover Text is: "You are free to copy and modify this GNU Manual. 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The section’s virtual memory address and load memory address must be the overlay’s mapped and load addresses. Identifying overlays with sections allows <small>GDB</small> to determine the appropriate address of a function or variable, depending on whether the overlay is mapped or not. </p> <p><small>GDB</small>’s overlay commands all start with the word <code>overlay</code>; you can abbreviate this as <code>ov</code> or <code>ovly</code>. The commands are: </p> <dl compact="compact"> <dt><code>overlay off</code></dt> <dd><a name="index-overlay"></a> <p>Disable <small>GDB</small>’s overlay support. When overlay support is disabled, <small>GDB</small> assumes that all functions and variables are always present at their mapped addresses. By default, <small>GDB</small>’s overlay support is disabled. </p> </dd> <dt><code>overlay manual</code></dt> <dd><a name="index-manual-overlay-debugging"></a> <p>Enable <em>manual</em> overlay debugging. In this mode, <small>GDB</small> relies on you to tell it which overlays are mapped, and which are not, using the <code>overlay map-overlay</code> and <code>overlay unmap-overlay</code> commands described below. </p> </dd> <dt><code>overlay map-overlay <var>overlay</var></code></dt> <dt><code>overlay map <var>overlay</var></code></dt> <dd><a name="index-map-an-overlay"></a> <p>Tell <small>GDB</small> that <var>overlay</var> is now mapped; <var>overlay</var> must be the name of the object file section containing the overlay. When an overlay is mapped, <small>GDB</small> assumes it can find the overlay’s functions and variables at their mapped addresses. <small>GDB</small> assumes that any other overlays whose mapped ranges overlap that of <var>overlay</var> are now unmapped. </p> </dd> <dt><code>overlay unmap-overlay <var>overlay</var></code></dt> <dt><code>overlay unmap <var>overlay</var></code></dt> <dd><a name="index-unmap-an-overlay"></a> <p>Tell <small>GDB</small> that <var>overlay</var> is no longer mapped; <var>overlay</var> must be the name of the object file section containing the overlay. When an overlay is unmapped, <small>GDB</small> assumes it can find the overlay’s functions and variables at their load addresses. </p> </dd> <dt><code>overlay auto</code></dt> <dd><p>Enable <em>automatic</em> overlay debugging. In this mode, <small>GDB</small> consults a data structure the overlay manager maintains in the inferior to see which overlays are mapped. For details, see <a href="Automatic-Overlay-Debugging.html#Automatic-Overlay-Debugging">Automatic Overlay Debugging</a>. </p> </dd> <dt><code>overlay load-target</code></dt> <dt><code>overlay load</code></dt> <dd><a name="index-reloading-the-overlay-table"></a> <p>Re-read the overlay table from the inferior. Normally, <small>GDB</small> re-reads the table <small>GDB</small> automatically each time the inferior stops, so this command should only be necessary if you have changed the overlay mapping yourself using <small>GDB</small>. This command is only useful when using automatic overlay debugging. </p> </dd> <dt><code>overlay list-overlays</code></dt> <dt><code>overlay list</code></dt> <dd><a name="index-listing-mapped-overlays"></a> <p>Display a list of the overlays currently mapped, along with their mapped addresses, load addresses, and sizes. </p> </dd> </dl> <p>Normally, when <small>GDB</small> prints a code address, it includes the name of the function the address falls in: </p> <div class="smallexample"> <pre class="smallexample">(gdb) print main $3 = {int ()} 0x11a0 <main> </pre></div> <p>When overlay debugging is enabled, <small>GDB</small> recognizes code in unmapped overlays, and prints the names of unmapped functions with asterisks around them. For example, if <code>foo</code> is a function in an unmapped overlay, <small>GDB</small> prints it this way: </p> <div class="smallexample"> <pre class="smallexample">(gdb) overlay list No sections are mapped. (gdb) print foo $5 = {int (int)} 0x100000 <*foo*> </pre></div> <p>When <code>foo</code>’s overlay is mapped, <small>GDB</small> prints the function’s name normally: </p> <div class="smallexample"> <pre class="smallexample">(gdb) overlay list Section .ov.foo.text, loaded at 0x100000 - 0x100034, mapped at 0x1016 - 0x104a (gdb) print foo $6 = {int (int)} 0x1016 <foo> </pre></div> <p>When overlay debugging is enabled, <small>GDB</small> can find the correct address for functions and variables in an overlay, whether or not the overlay is mapped. This allows most <small>GDB</small> commands, like <code>break</code> and <code>disassemble</code>, to work normally, even on unmapped code. However, <small>GDB</small>’s breakpoint support has some limitations: </p> <ul> <li> <a name="index-breakpoints-in-overlays"></a> <a name="index-overlays_002c-setting-breakpoints-in"></a> You can set breakpoints in functions in unmapped overlays, as long as <small>GDB</small> can write to the overlay at its load address. </li><li> <small>GDB</small> can not set hardware or simulator-based breakpoints in unmapped overlays. However, if you set a breakpoint at the end of your overlay manager (and tell <small>GDB</small> which overlays are now mapped, if you are using manual overlay management), <small>GDB</small> will re-set its breakpoints properly. </li></ul> <hr> <div class="header"> <p> Next: <a href="Automatic-Overlay-Debugging.html#Automatic-Overlay-Debugging" accesskey="n" rel="next">Automatic Overlay Debugging</a>, Previous: <a href="How-Overlays-Work.html#How-Overlays-Work" accesskey="p" rel="prev">How Overlays Work</a>, Up: <a href="Overlays.html#Overlays" accesskey="u" rel="up">Overlays</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> </div> </body> </html>