Re: [PATCH] [gdb/build] Workaround gcc PR113599

[Tom de Vries <tdevries@suse.de>]

On 1/25/24 16:27, Sam James wrote:
> 
> Tom de Vries <tdevries@suse.de> writes:
> 
>> Since gcc commit d3f48f68227 ("c++: non-dependent .* operand folding
>> [PR112427]"), with gdb we run into PR gcc/113599 [1], a wrong-code bug, as
>> reported in PR build/31281.
>>
>> Work around this by flipping inherit order:
>> ...
>> -class thread_info : public refcounted_object,
>> -		    public intrusive_list_node<thread_info>
>> +class thread_info : public intrusive_list_node<thread_info>,
>> +		    public refcounted_object
>> ...
>>
>> An argument could be made that this isn't necessary, because this occurred in
>> an unreleased gcc version.
>>
>> However, I think it could be useful when bisecting gcc for other problems in
>> building gdb.  Having this workaround means the bisect won't reintroduce the
>> problem.  Furthermore, the workaround is harmless.
>>
>> Tested on Fedora rawhide x86_64.
>>
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31281
>>
>> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113599
>> ---
>>   gdb/gdbthread.h | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
>> index e7035d40ad4..1d9730fd1fa 100644
>> --- a/gdb/gdbthread.h
>> +++ b/gdb/gdbthread.h
>> @@ -244,10 +244,11 @@ using private_thread_info_up = std::unique_ptr<private_thread_info>;
>>      strong reference, and is thus not accounted for in the thread's
>>      refcount.
>>   
>> -   The intrusive_list_node base links threads in a per-inferior list.  */
>> +   The intrusive_list_node base links threads in a per-inferior list.
>> +   We place it first in the inherit orer to work around PR gcc/113599.  */
> 
> order
> 

Thanks for catching that, fixed.

- Tom

>>   
>> -class thread_info : public refcounted_object,
>> -		    public intrusive_list_node<thread_info>
>> +class thread_info : public intrusive_list_node<thread_info>,
>> +		    public refcounted_object
>>   {
>>   public:
>>     explicit thread_info (inferior *inf, ptid_t ptid);
>>
>> base-commit: 726f209eb1b05842d816eac8b0b8f9c7f6cd9fbc
>