27.23 gdb/mi Support Commands

Since new commands and features get regularly added to gdb/mi, some commands are available to help front-ends query the debugger about support for these capabilities. Similarly, it is also possible to query gdb about target support of certain features.

The -info-gdb-mi-command Command

Synopsis

      -info-gdb-mi-command cmd_name

Query support for the gdb/mi command named cmd_name.

Note that the dash (-) starting all gdb/mi commands is technically not part of the command name (see GDB/MI Input Syntax), and thus should be omitted in cmd_name. However, for ease of use, this command also accepts the form with the leading dash.

gdb Command

There is no corresponding gdb command.

Result

The result is a tuple. There is currently only one field:

`exists'

This field is equal to "true" if the gdb/mi command exists, "false" otherwise.

Example

Here is an example where the gdb/mi command does not exist:

     -info-gdb-mi-command unsupported-command
     ^done,command={exists="false"}

And here is an example where the gdb/mi command is known to the debugger:

     -info-gdb-mi-command symbol-list-lines
     ^done,command={exists="true"}

The -list-features Command

Returns a list of particular features of the MI protocol that this version of gdb implements. A feature can be a command, or a new field in an output of some command, or even an important bugfix. While a frontend can sometimes detect presence of a feature at runtime, it is easier to perform detection at debugger startup.

The command returns a list of strings, with each string naming an available feature. Each returned string is just a name, it does not have any internal structure. The list of possible feature names is given below.

Example output:

     (gdb) -list-features
     ^done,result=["feature1","feature2"]

The current list of features is:

`frozen-varobjs'

Indicates support for the -var-set-frozen command, as well as possible presense of the frozen field in the output of -varobj-create.

`pending-breakpoints'

Indicates support for the -f option to the -break-insert command.

`python'

Indicates Python scripting support, Python-based pretty-printing commands, and possible presence of the `display_hint' field in the output of -var-list-children

`thread-info'

Indicates support for the -thread-info command.

`data-read-memory-bytes'

Indicates support for the -data-read-memory-bytes and the -data-write-memory-bytes commands.

`breakpoint-notifications'

Indicates that changes to breakpoints and breakpoints created via the CLI will be announced via async records.

`ada-task-info'

Indicates support for the -ada-task-info command.

`language-option'

Indicates that all gdb/mi commands accept the --language option (see Context management).

`info-gdb-mi-command'

Indicates support for the -info-gdb-mi-command command.

`undefined-command-error-code'

Indicates support for the "undefined-command" error code in error result records, produced when trying to execute an undefined gdb/mi command (see GDB/MI Result Records).

`exec-run-start-option'

Indicates that the -exec-run command supports the --start option (see GDB/MI Program Execution).

The -list-target-features Command

Returns a list of particular features that are supported by the target. Those features affect the permitted MI commands, but unlike the features reported by the -list-features command, the features depend on which target GDB is using at the moment. Whenever a target can change, due to commands such as -target-select, -target-attach or -exec-run, the list of target features may change, and the frontend should obtain it again. Example output:

     (gdb) -list-target-features
     ^done,result=["async"]

The current list of features is:

`async'

Indicates that the target is capable of asynchronous command execution, which means that gdb will accept further commands while the target is running.

`reverse'

Indicates that the target is capable of reverse execution. See Reverse Execution, for more information.