Create new parameters with Gdb Python API

Question

I can't figure out how to fully define a new parameter using the Python API in Gdb. A script that I source contains the following:

python
param = gdb.Parameter("test", gdb.COMMAND_NONE, gdb.PARAM_OPTIONAL_FILENAME)
param.set_doc = "This is the documentation" --> throws exception
end

I change and show its value in Gdb using:

(gdb) set test "hello world"
This command is not documented.
(gdb) show test
This command is not documented. "hello world"

The Gdb documentation mentions Parameter.set_doc, but when I try to assign to it I get the exception:

AttributeError: 'gdb.Parameter' object has no attribute 'set_doc'

How can I add this documentation, or how can I stop this "not documented" message from printing?

Mark Plotnick · Accepted Answer · 2017-05-16 02:57:16Z

1

Although it may be possible to create a new parameter in gdb by instantiating gdb.Parameter directly and adding attributes later - maybe someone can answer that - the usual way is to define a new class, a subclass of gdb.Parameter, defining the necessary attributes such as set_doc in that class, and instantiating that class. Here's your example, reworked:

$ cat test.py
class TestParameter(gdb.Parameter):
    """Manage the test parameter.

    Usage: set test filename
           show test
    """
    set_doc = "This is the single-line documentation for set test"
    show_doc = "This is the single-line documentation for show test"
    def __init__(self):
        super(TestParameter, self).__init__("test", gdb.COMMAND_NONE,
                                             gdb.PARAM_OPTIONAL_FILENAME)
        self.value=""
    def get_set_string(self):
        return "You have set test to " + self.value
    def get_show_string(self, _):
        return "The value of test is " + self.value

TestParameter()

$ gdb -q
(gdb) source test.py

The following shows where and how the various doc strings are displayed:

(gdb) help set test
This is the single-line documentation for set test
Manage the test parameter.

    Usage: set test filename
           show test

(gdb) help show test
This is the single-line documentation for show test
Manage the test parameter.

    Usage: set test filename
           show test

(gdb) help set
...
List of set subcommands:
...
set test -- This is the single-line documentation for set test
...

Here's the output produced by set and show:

(gdb) set test .profile
You have set test to .profile
(gdb) show test
The value of test is .profile

edited May 16, 2017 at 2:57

answered May 15, 2017 at 17:00

Mark Plotnick

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2 Comments

gospes Over a year ago

Great example +1! thx. Is it also possible to silence the set command? I'm using the set command in a gdb function which now prints a doc string I don't want to see.

Mark Plotnick Over a year ago

I haven't found a way to stop set of a user-defined parameter from producing output. If you make get_set_string return "", gdb will output an empty line. If you don't define get_set_string, gdb will output the value of set_doc. If you don't define get_set_string and don't define set_doc, gdb will output "This command is not documented."

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