105 lines
5.1 KiB
HTML
105 lines
5.1 KiB
HTML
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<html lang="en">
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<head>
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<title>In-Process Agent - 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="prev" href="JIT-Interface.html#JIT-Interface" title="JIT Interface">
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<link rel="next" href="GDB-Bugs.html#GDB-Bugs" title="GDB Bugs">
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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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</head>
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<body>
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<div class="node">
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<a name="In-Process-Agent"></a>
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<a name="In_002dProcess-Agent"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="GDB-Bugs.html#GDB-Bugs">GDB Bugs</a>,
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Previous: <a rel="previous" accesskey="p" href="JIT-Interface.html#JIT-Interface">JIT Interface</a>,
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Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a>
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<hr>
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</div>
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<h2 class="chapter">30 In-Process Agent</h2>
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<p><a name="index-debugging-agent-3161"></a>The traditional debugging model is conceptually low-speed, but works fine,
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because most bugs can be reproduced in debugging-mode execution. However,
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as multi-core or many-core processors are becoming mainstream, and
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multi-threaded programs become more and more popular, there should be more
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and more bugs that only manifest themselves at normal-mode execution, for
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example, thread races, because debugger's interference with the program's
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timing may conceal the bugs. On the other hand, in some applications,
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it is not feasible for the debugger to interrupt the program's execution
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long enough for the developer to learn anything helpful about its behavior.
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If the program's correctness depends on its real-time behavior, delays
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introduced by a debugger might cause the program to fail, even when the
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code itself is correct. It is useful to be able to observe the program's
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behavior without interrupting it.
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<p>Therefore, traditional debugging model is too intrusive to reproduce
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some bugs. In order to reduce the interference with the program, we can
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reduce the number of operations performed by debugger. The
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<dfn>In-Process Agent</dfn>, a shared library, is running within the same
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process with inferior, and is able to perform some debugging operations
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itself. As a result, debugger is only involved when necessary, and
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performance of debugging can be improved accordingly. Note that
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interference with program can be reduced but can't be removed completely,
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because the in-process agent will still stop or slow down the program.
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<p>The in-process agent can interpret and execute Agent Expressions
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(see <a href="Agent-Expressions.html#Agent-Expressions">Agent Expressions</a>) during performing debugging operations. The
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agent expressions can be used for different purposes, such as collecting
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data in tracepoints, and condition evaluation in breakpoints.
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<p><a name="Control-Agent"></a>You can control whether the in-process agent is used as an aid for
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debugging with the following commands:
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<a name="index-set-agent-on-3162"></a>
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<dl><dt><code>set agent on</code><dd>Causes the in-process agent to perform some operations on behalf of the
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debugger. Just which operations requested by the user will be done
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by the in-process agent depends on the its capabilities. For example,
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if you request to evaluate breakpoint conditions in the in-process agent,
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and the in-process agent has such capability as well, then breakpoint
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conditions will be evaluated in the in-process agent.
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<p><a name="index-set-agent-off-3163"></a><br><dt><code>set agent off</code><dd>Disables execution of debugging operations by the in-process agent. All
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of the operations will be performed by <span class="sc">gdb</span>.
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<p><a name="index-show-agent-3164"></a><br><dt><code>show agent</code><dd>Display the current setting of execution of debugging operations by
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the in-process agent.
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</dl>
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<ul class="menu">
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<li><a accesskey="1" href="In_002dProcess-Agent-Protocol.html#In_002dProcess-Agent-Protocol">In-Process Agent Protocol</a>
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</ul>
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</body></html>
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