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| <h3 class="section">27.4 <span class="sc">gdb/mi</span> Development and Front Ends</h3> |
| |
| <p><a name="index-g_t_0040sc_007bgdb_002fmi_007d-development-2966"></a> |
| The application which takes the MI output and presents the state of the |
| program being debugged to the user is called a <dfn>front end</dfn>. |
| |
| <p>Since <span class="sc">gdb/mi</span> is used by a variety of front ends to <span class="sc">gdb</span>, changes |
| to the MI interface may break existing usage. This section describes how the |
| protocol changes and how to request previous version of the protocol when it |
| does. |
| |
| <p>Some changes in MI need not break a carefully designed front end, and |
| for these the MI version will remain unchanged. The following is a |
| list of changes that may occur within one level, so front ends should |
| parse MI output in a way that can handle them: |
| |
| <ul> |
| <li>New MI commands may be added. |
| |
| <li>New fields may be added to the output of any MI command. |
| |
| <li>The range of values for fields with specified values, e.g., |
| <code>in_scope</code> (see <a href="_002dvar_002dupdate.html#g_t_002dvar_002dupdate">-var-update</a>) may be extended. |
| |
| <!-- The format of field's content e.g type prefix, may change so parse it --> |
| <!-- at your own risk. Yes, in general? --> |
| <!-- The order of fields may change? Shouldn't really matter but it might --> |
| <!-- resolve inconsistencies. --> |
| </ul> |
| |
| <p>If the changes are likely to break front ends, the MI version level |
| will be increased by one. The new versions of the MI protocol are not compatible |
| with the old versions. Old versions of MI remain available, allowing front ends |
| to keep using them until they are modified to use the latest MI version. |
| |
| <p>Since <code>--interpreter=mi</code> always points to the latest MI version, it is |
| recommended that front ends request a specific version of MI when launching |
| <span class="sc">gdb</span> (e.g. <code>--interpreter=mi2</code>) to make sure they get an |
| interpreter with the MI version they expect. |
| |
| <p>The following table gives a summary of the the released versions of the MI |
| interface: the version number, the version of GDB in which it first appeared |
| and the breaking changes compared to the previous version. |
| |
| <p><table summary=""><tr align="left"><th valign="top" width="5%">MI version </th><th valign="top" width="5%">GDB version </th><th valign="top" width="90%">Breaking changes |
| |
| <p><br></th></tr><tr align="left"><td valign="top" width="5%"><div align="center">1</div> |
| <p></td><td valign="top" width="5%"> |
| <div align="center">5.1</div> |
| <p></td><td valign="top" width="90%"> |
| None |
| |
| <p><br></td></tr><tr align="left"><td valign="top" width="5%"><div align="center">2</div> |
| <p></td><td valign="top" width="5%"> |
| <div align="center">6.0</div> |
| <p></td><td valign="top" width="90%"> |
| |
| <ul> |
| <li>The <code>-environment-pwd</code>, <code>-environment-directory</code> and |
| <code>-environment-path</code> commands now returns values using the MI output |
| syntax, rather than CLI output syntax. |
| |
| <li><code>-var-list-children</code>'s <code>children</code> result field is now a list, rather |
| than a tuple. |
| |
| <li><code>-var-update</code>'s <code>changelist</code> result field is now a list, rather than |
| a tuple. |
| </ul> |
| <br></td></tr></table> |
| |
| <p>The best way to avoid unexpected changes in MI that might break your front |
| end is to make your project known to <span class="sc">gdb</span> developers and |
| follow development on <a href="mailto:gdb@sourceware.org">gdb@sourceware.org</a> and |
| <a href="mailto:gdb-patches@sourceware.org">gdb-patches@sourceware.org</a>. |
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