90 lines
4.5 KiB
HTML
90 lines
4.5 KiB
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<title>Stub Contents - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Remote-Stub.html#Remote-Stub" title="Remote Stub">
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<link rel="next" href="Bootstrapping.html#Bootstrapping" title="Bootstrapping">
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Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
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and with the Back-Cover Texts as in (a) below.
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<div class="node">
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<a name="Stub-Contents"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Bootstrapping.html#Bootstrapping">Bootstrapping</a>,
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Up: <a rel="up" accesskey="u" href="Remote-Stub.html#Remote-Stub">Remote Stub</a>
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<hr>
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</div>
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<h4 class="subsection">20.5.1 What the Stub Can Do for You</h4>
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<p><a name="index-remote-serial-stub-1424"></a>The debugging stub for your architecture supplies these three
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subroutines:
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<dl>
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<dt><code>set_debug_traps</code><dd><a name="index-set_005fdebug_005ftraps-1425"></a><a name="index-remote-serial-stub_002c-initialization-1426"></a>This routine arranges for <code>handle_exception</code> to run when your
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program stops. You must call this subroutine explicitly in your
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program's startup code.
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<br><dt><code>handle_exception</code><dd><a name="index-handle_005fexception-1427"></a><a name="index-remote-serial-stub_002c-main-routine-1428"></a>This is the central workhorse, but your program never calls it
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explicitly—the setup code arranges for <code>handle_exception</code> to
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run when a trap is triggered.
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<p><code>handle_exception</code> takes control when your program stops during
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execution (for example, on a breakpoint), and mediates communications
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with <span class="sc">gdb</span> on the host machine. This is where the communications
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protocol is implemented; <code>handle_exception</code> acts as the <span class="sc">gdb</span>
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representative on the target machine. It begins by sending summary
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information on the state of your program, then continues to execute,
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retrieving and transmitting any information <span class="sc">gdb</span> needs, until you
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execute a <span class="sc">gdb</span> command that makes your program resume; at that point,
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<code>handle_exception</code> returns control to your own code on the target
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machine.
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<br><dt><code>breakpoint</code><dd><a name="index-g_t_0040code_007bbreakpoint_007d-subroutine_002c-remote-1429"></a>Use this auxiliary subroutine to make your program contain a
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breakpoint. Depending on the particular situation, this may be the only
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way for <span class="sc">gdb</span> to get control. For instance, if your target
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machine has some sort of interrupt button, you won't need to call this;
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pressing the interrupt button transfers control to
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<code>handle_exception</code>—in effect, to <span class="sc">gdb</span>. On some machines,
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simply receiving characters on the serial port may also trigger a trap;
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again, in that situation, you don't need to call <code>breakpoint</code> from
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your own program—simply running ‘<samp><span class="samp">target remote</span></samp>’ from the host
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<span class="sc">gdb</span> session gets control.
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<p>Call <code>breakpoint</code> if none of these is true, or if you simply want
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to make certain your program stops at a predetermined point for the
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start of your debugging session.
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</dl>
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</body></html>
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