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 Next: <a href="GDB_002fMI-Command-Syntax.html#GDB_002fMI-Command-Syntax" accesskey="n" rel="next">GDB/MI Command Syntax</a>, Up: <a href="GDB_002fMI.html#GDB_002fMI" accesskey="u" rel="up">GDB/MI</a> &nbsp; [<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>
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 <hr>
 <a name="GDB_002fMI-General-Design-1"></a>
 <h3 class="section">27.1 <small>GDB/MI</small> General Design</h3>
 <a name="index-GDB_002fMI-General-Design"></a>

 <p>Interaction of a <small>GDB/MI</small> frontend with <small>GDB</small> involves three
 parts&mdash;commands sent to <small>GDB</small>, responses to those commands
 and notifications.  Each command results in exactly one response,
 indicating either successful completion of the command, or an error.
 For the commands that do not resume the target, the response contains the
 requested information.  For the commands that resume the target, the
 response only indicates whether the target was successfully resumed.
 Notifications is the mechanism for reporting changes in the state of the
 target, or in <small>GDB</small> state, that cannot conveniently be associated with
 a command and reported as part of that command response.
 </p>
 <p>The important examples of notifications are:
 </p><ul>
 <li> Exec notifications.  These are used to report changes in
 target state&mdash;when a target is resumed, or stopped.  It would not
 be feasible to include this information in response of resuming
 commands, because one resume commands can result in multiple events in
 different threads.  Also, quite some time may pass before any event
 happens in the target, while a frontend needs to know whether the resuming
 command itself was successfully executed.

 </li><li> Console output, and status notifications.  Console output
 notifications are used to report output of CLI commands, as well as
 diagnostics for other commands.  Status notifications are used to
 report the progress of a long-running operation.  Naturally, including
 this information in command response would mean no output is produced
 until the command is finished, which is undesirable.

 </li><li> General notifications.  Commands may have various side effects on
 the <small>GDB</small> or target state beyond their official purpose.  For example,
 a command may change the selected thread.  Although such changes can
 be included in command response, using notification allows for more
 orthogonal frontend design.

 </li></ul>

 <p>There&rsquo;s no guarantee that whenever an MI command reports an error,
 <small>GDB</small> or the target are in any specific state, and especially,
 the state is not reverted to the state before the MI command was
 processed.  Therefore, whenever an MI command results in an error,
 we recommend that the frontend refreshes all the information shown in
 the user interface.
 </p>

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	<p>
	Next: <a href="GDB_002fMI-Command-Syntax.html#GDB_002fMI-Command-Syntax" accesskey="n" rel="next">GDB/MI Command Syntax</a>, Up: <a href="GDB_002fMI.html#GDB_002fMI" accesskey="u" rel="up">GDB/MI</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>
	<hr>
	<a name="GDB_002fMI-General-Design-1"></a>
	<h3 class="section">27.1 <small>GDB/MI</small> General Design</h3>
	<a name="index-GDB_002fMI-General-Design"></a>

	<p>Interaction of a <small>GDB/MI</small> frontend with <small>GDB</small> involves three
	parts—commands sent to <small>GDB</small>, responses to those commands
	and notifications. Each command results in exactly one response,
	indicating either successful completion of the command, or an error.
	For the commands that do not resume the target, the response contains the
	requested information. For the commands that resume the target, the
	response only indicates whether the target was successfully resumed.
	Notifications is the mechanism for reporting changes in the state of the
	target, or in <small>GDB</small> state, that cannot conveniently be associated with
	a command and reported as part of that command response.
	</p>
	<p>The important examples of notifications are:
	</p><ul>
	<li> Exec notifications. These are used to report changes in
	target state—when a target is resumed, or stopped. It would not
	be feasible to include this information in response of resuming
	commands, because one resume commands can result in multiple events in
	different threads. Also, quite some time may pass before any event
	happens in the target, while a frontend needs to know whether the resuming
	command itself was successfully executed.

	</li><li> Console output, and status notifications. Console output
	notifications are used to report output of CLI commands, as well as
	diagnostics for other commands. Status notifications are used to
	report the progress of a long-running operation. Naturally, including
	this information in command response would mean no output is produced
	until the command is finished, which is undesirable.

	</li><li> General notifications. Commands may have various side effects on
	the <small>GDB</small> or target state beyond their official purpose. For example,
	a command may change the selected thread. Although such changes can
	be included in command response, using notification allows for more
	orthogonal frontend design.

	</li></ul>

	<p>There’s no guarantee that whenever an MI command reports an error,
	<small>GDB</small> or the target are in any specific state, and especially,
	the state is not reverted to the state before the MI command was
	processed. Therefore, whenever an MI command results in an error,
	we recommend that the frontend refreshes all the information shown in
	the user interface.
	</p>

	<table class="menu" border="0" cellspacing="0">
	<tr><td align="left" valign="top">• <a href="Context-management.html#Context-management" accesskey="1">Context management</a>:</td><td>  </td><td align="left" valign="top">
	</td></tr>
	<tr><td align="left" valign="top">• <a href="Asynchronous-and-non_002dstop-modes.html#Asynchronous-and-non_002dstop-modes" accesskey="2">Asynchronous and non-stop modes</a>:</td><td>  </td><td align="left" valign="top">
	</td></tr>
	<tr><td align="left" valign="top">• <a href="Thread-groups.html#Thread-groups" accesskey="3">Thread groups</a>:</td><td>  </td><td align="left" valign="top">
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	<p>
	Next: <a href="GDB_002fMI-Command-Syntax.html#GDB_002fMI-Command-Syntax" accesskey="n" rel="next">GDB/MI Command Syntax</a>, Up: <a href="GDB_002fMI.html#GDB_002fMI" accesskey="u" rel="up">GDB/MI</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>
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