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| <h3 class="section">27.1 <span class="sc">gdb/mi</span> General Design</h3> |
| |
| <p><a name="index-GDB_002fMI-General-Design-2002"></a> |
| Interaction of a <span class="sc">GDB/MI</span> frontend with <span class="sc">gdb</span> involves three |
| parts—commands sent to <span class="sc">gdb</span>, 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 <span class="sc">gdb</span> state, that cannot conveniently be associated with |
| a command and reported as part of that command response. |
| |
| <p>The important examples of notifications are: |
| <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>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>General notifications. Commands may have various side effects on |
| the <span class="sc">gdb</span> 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. |
| |
| </ul> |
| |
| <p>There's no guarantee that whenever an MI command reports an error, |
| <span class="sc">gdb</span> 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. |
| |
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| <li><a accesskey="1" href="Context-management.html#Context-management">Context management</a> |
| <li><a accesskey="2" href="Asynchronous-and-non_002dstop-modes.html#Asynchronous-and-non_002dstop-modes">Asynchronous and non-stop modes</a> |
| <li><a accesskey="3" href="Thread-groups.html#Thread-groups">Thread groups</a> |
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