Re: GDB 7.99.91 available for testing

Simon Marchi
2017-05-16T21:22:23Z

On 2017-05-16 16:49, Yao Qi wrote:
> On 17-05-16 09:51:42, Simon Marchi wrote:
>>
>> So indeed, the problem is due to the ordering of the _initialize
>> functions
>> that changed, _initialize_printcmd used to be called before
>> _initialize_infcmd, now it's the reverse.
>>
>> When it works, the timeline of events to be able to get the tty alias
>> working is the following:
>>
>> 1. The "set" command is registered as a prefix command in printcmd.c,
>> which
>> adds it to the global command list (cmdlist). setlist is the list of
>> its
>> subcommands.
>> 2. The "set inferior-tty" command is added as a child of "set" (i.e.
>> it's
>> inserted into setlist) in infcmd.c.
>> 3. The "tty" alias is created for "set inferior-tty" in infcmd.c.
>> This
>> looks up "set" in cmdlist, then "inferior-tty" in the subcommands of
>> "set".
>> It's found and everyone is happy.
>>
>> With the _initialize functions called in a different order, steps are
>> executed in the order 2-3-1. When we try to create the alias, the
>> "set"
>> command has not been created and is therefore not part of cmdlist. We
>> can't
>> find the "set inferior-tty" command, so the alias is not created.
>
> When we try to create the alias (in step 3), setlist is already created
> in step 2, but it is not linked with cmdlist. The command "set
> inferior-tty" is created in step 2 too. Since step 2 and step 3 are
> close to each other (in _initialize_infcmd), we can pass the "set
> inferior-tty" cmd_list_element to the place we create alias, like this,
>
> cmd_name = "inferior-tty";
> c = lookup_cmd (&cmd_name, setlist, "", -1, 1);
> gdb_assert (c != NULL);
> add_alias_cmd ("tty", c, class_alias, 0, &cmdlist);
>
> this makes sure we add alias "tty" under cmdlist, and it is alias to
> "set inferior-tty". Step 1 just links setlist and cmdlist together.
>
>>
>> I think the core issue is that it's currently possible to create
>> subcommands
>> for prefixes that have not been created yet. We need some way of
>> ensuring
>> some kind of ordering. Here are some ideas:
>>
>
> How is the patch below? I run regress tests yet, and it still needs
> some comments.

It's very clean, I like it. I think it's good for master and 8.0. Do
you want to finish it or do you want me to pick it up?

I have enhanced gdb.base/set-inferior-tty.exp to exercise the alias, it
could be added to your patch:

https://github.com/simark/binutils-gdb/commit/1a8bcb5dbc0dde3d8a4d3f73d0a057b3831902dd#diff-2f94d545bf202185ae6a6022ebfa93bc

Thanks,

Simon