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| <h3 class="section">14.4 Overlay Sample Program</h3> |
| |
| <p><a name="index-overlay-example-program-776"></a> |
| When linking a program which uses overlays, you must place the overlays |
| at their load addresses, while relocating them to run at their mapped |
| addresses. To do this, you must write a linker script (see <a href="../ld/Overlay-Description.html#Overlay-Description">Overlay Description</a>). Unfortunately, |
| since linker scripts are specific to a particular host system, target |
| architecture, and target memory layout, this manual cannot provide |
| portable sample code demonstrating <span class="sc">gdb</span>'s overlay support. |
| |
| <p>However, the <span class="sc">gdb</span> source distribution does contain an overlaid |
| program, with linker scripts for a few systems, as part of its test |
| suite. The program consists of the following files from |
| <samp><span class="file">gdb/testsuite/gdb.base</span></samp>: |
| |
| <dl> |
| <dt><samp><span class="file">overlays.c</span></samp><dd>The main program file. |
| <br><dt><samp><span class="file">ovlymgr.c</span></samp><dd>A simple overlay manager, used by <samp><span class="file">overlays.c</span></samp>. |
| <br><dt><samp><span class="file">foo.c</span></samp><dt><samp><span class="file">bar.c</span></samp><dt><samp><span class="file">baz.c</span></samp><dt><samp><span class="file">grbx.c</span></samp><dd>Overlay modules, loaded and used by <samp><span class="file">overlays.c</span></samp>. |
| <br><dt><samp><span class="file">d10v.ld</span></samp><dt><samp><span class="file">m32r.ld</span></samp><dd>Linker scripts for linking the test program on the <code>d10v-elf</code> |
| and <code>m32r-elf</code> targets. |
| </dl> |
| |
| <p>You can build the test program using the <code>d10v-elf</code> GCC |
| cross-compiler like this: |
| |
| <pre class="smallexample"> $ d10v-elf-gcc -g -c overlays.c |
| $ d10v-elf-gcc -g -c ovlymgr.c |
| $ d10v-elf-gcc -g -c foo.c |
| $ d10v-elf-gcc -g -c bar.c |
| $ d10v-elf-gcc -g -c baz.c |
| $ d10v-elf-gcc -g -c grbx.c |
| $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \ |
| baz.o grbx.o -Wl,-Td10v.ld -o overlays |
| </pre> |
| <p>The build process is identical for any other architecture, except that |
| you must substitute the appropriate compiler and linker script for the |
| target system for <code>d10v-elf-gcc</code> and <code>d10v.ld</code>. |
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