Re: [PATCH] gdb/DAP: Add customRequest

[Tom Tromey <tom@tromey.com>]

>>>>> "Simon" == Simon Farre via Gdb-patches <gdb-patches@sourceware.org> writes:

Simon> This patch introduces the customRequest, which allows for DA's (debug adapters)
Simon> that want to use the full extent of GDB's functionality by working a bit
Simon> like the extension of `gdb.Command`

Seems reasonable to me.

Simon> Unfortunately, there's nothing about such a request in the
Simon> DAP-spec, but I'd argue that's really irrelevant; the largest
Simon> code editor for debug adapter protocol implementers, has a notion
Simon> of it, though it's up to DA-implementers to make sure they
Simon> understand their own requests.

Makes sense.

Simon> Beyond this patch, documentation would be needed also, to document how
Simon> to create customRequests, like the one above. I'm hoping Eli can provide me with
Simon> some direction here.

There's a DAP node in the docs where I think it would make sense to
document the existence of the custom request.  For implementing requests
themselves, I think a new node in python.texi would be appropriate.

>> @server.custom_request("foo")
>> def fooRequestHandler(argumentBaz):
>> # full Python interpreter access, full access to all of GDB, like we're @ the CLI
>> # say goodbye to MI! Yay! :P
>> return { "bar": gdb.execute("print foo", to_string=True), "someParam": argumentBaz }

Simon> +@request("customRequest")
Simon> +def custom_request_handler(**args):
Simon> +    global _custom_requests
Simon> +    cmd = args["command"]
Simon> +    if _custom_requests.get(cmd) is not None:
Simon> +        return _custom_requests[cmd](args["args"])

An issue here is that the DAP thread can't directly invoke code in gdb
-- basically the 'gdb' module is off-limits.  This is why there are
decorators to assert that a given function is on the DAP thread or gdb
thread.  This rule is in place because the core of gdb isn't
thread-safe.

Probably the fix is as simple as wrapping the call with
send_gdb_with_response, and having the custom_request decorator
use in_gdb_thread.

Tom