gcc warning with "some variable may be used uninitialized in this function [-Wmaybe-uninitialized]" when building under msys

[Pedro Alves]

On 10/09/2018 08:54 PM, Pedro Alves wrote:
> On 10/09/2018 08:33 PM, Tom Tromey wrote:
>>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
>>
>>>> It would be good if gcc could recognize std::optional and not issue the
>>>> warning when it is used.  Perhaps gdb could then just always use
>>>> optional for the maybe-not-initialized cases.
>>
>> Pedro> Really not sure whether that is possible.  I think there's hope
>> Pedro> that GCC value tracking becomes smart enough that these
>> Pedro> std::optional-related warnings end up disappearing (which usually
>> Pedro> means the code will optimize better too).  Fingers crossed, at least.
>>
>> For gdb::optional, I think it would be good enough if we could simply
>> suppress the warning and make operator* assert that the object was
>> instantiated.  Perhaps std::optional could enforce this in debug mode as
>> well.
> 
> Last I tried, I couldn't find a way to suppress the warning from
> gdb::optional.  The warning triggers in code that belongs to
> T in gdb::optional<T>.

Maybe we could make gdb::optional's ctor initialize the payload
only in devel mode, leave it uninitialized in release mode,
and add back -Werror for that warning.  We'd see the warnings in
release mode, but releases don't use -Werror so it's less of
an issue.

Doesn't really fix the issue though, just papers over it.
Not sure that really helps.

Thanks,
Pedro Alves