Re: [PATCH] Fix crash with "maintenance print arc"

[Andrew Burgess <aburgess@redhat.com>]

Luis Machado via Gdb-patches <gdb-patches@sourceware.org> writes:

> On 4/28/22 16:26, Tom Tromey wrote:
>>>>>>> "Luis" == Luis Machado via Gdb-patches <gdb-patches@sourceware.org> writes:
>> 
>> Luis> While doing something else, I noticed GDB crashed with
>> Luis> "maintenance print arc".
>> 
>> I think the bug here is that this uses add_show_prefix_cmd and not
>> add_basic_prefix_cmd.  See the appended, which also fixes the crash.
>
> Ah, you're right. It did look odd why we were feeding maint commands to 
> code that is supposed to handle show commands.
>
>> 
>> Luis> This happens because the code expects to find a "show" string pattern
>> Luis> within "maintenance print arc", since "arc" here is a prefix, and skip it.
>> Luis> In this case though, it won't find it, and we will have a bad pointer
>> Luis> getting dereferenced.
>> 
>> This looks reasonable to me.
>
> Should we prevent further situations like this by asserting that we 
> don't have a class_maintenance prefix being registered as a show
> prefix?

Would this not trigger for all the existing 'maint show ...' commands?

Thanks,
Andrew

>
>> 
>> Tom
>> 
>> diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
>> index 98bd1c4bc0a..3edfd466f3b 100644
>> --- a/gdb/arc-tdep.c
>> +++ b/gdb/arc-tdep.c
>> @@ -2474,11 +2474,11 @@ _initialize_arc_tdep ()
>>     /* Register ARC-specific commands with gdb.  */
>>   
>>     /* Add root prefix command for "maintenance print arc" commands.  */
>> -  add_show_prefix_cmd ("arc", class_maintenance,
>> -		       _("ARC-specific maintenance commands for printing GDB "
>> -			 "internal state."),
>> -		       &maintenance_print_arc_list,
>> -		       0, &maintenanceprintlist);
>> +  add_basic_prefix_cmd ("arc", class_maintenance,
>> +			_("ARC-specific maintenance commands for printing GDB "
>> +			  "internal state."),
>> +			&maintenance_print_arc_list,
>> +			0, &maintenanceprintlist);
>>   
>>     add_cmd ("arc-instruction", class_maintenance,
>>   	   dump_arc_instruction_command,