Re: scratch/igc fe90d556834: Make glyphs ambiguous roots

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Gerd Möllmann <gerd.moellmann@gmail.com> writes:

>> The doc
>> https://memory-pool-system.readthedocs.io/en/latest/topic/format.html#cautions
>> says:
>>
>>   1. The MPS guarantees that format methods have exclusive access to the
>>      object for the duration of the call. This guarantee may entail
>>      suspending arbitrary threads. The methods that manipulate the object
>>      must not perform any sort of inter-thread locking or communication.
>>   ...
>>
>>   6. Subject to the above constraints, format methods can freely access:
>>      a. memory inside the object or block that they have been asked to
>>         look at;
>>      b. MPS-managed memory in pools that do not protect their contents;
>>      c. memory not managed by the MPS.
>>
>> While the doc doesn't guarantee that all other (registered) threads are
>> suspended, it's hard to imagine what else MPS could do to stop other
>> threads from messing up the object.  (MPS must remove hardware barriers,
>> so that's not an option.)
>
> Good point, indeed.
>
> I've reverted that change. Thanks for checking!

By the same argument, I think we could simplify face_cache and
image_cache which both use IGC_OBJ_PTR_VEC at the moment. 
IGC_OBJ_PTR_VEC could then go completely.

WDYT?