Create new parameters with Gdb Python API - gdb

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?

Answer 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