bug#43177: Bug: Emacs 27.1 hangs forever in `FcCharSetSubtractCount' from '/usr/lib/libfontconfig.so.1'

[Robert Pluim]

>>>>> On Thu, 03 Sep 2020 15:28:45 +0200, Andreas Schwab 
>>>>> <schwab@linux-m68k.org> said:

    Andreas> On Sep 03 2020, Robert Pluim wrote:
    >>>>>>> On Thu, 03 Sep 2020 14:52:22 +0200, Andreas Schwab 
<schwab@linux-m68k.org> said:
    >> 
    Andreas> On Sep 03 2020, Robert Pluim wrote:
    >> >> tai-viet and han scripts. My GNU/Linux build uses 'Noto Sans Tai Viet'
    >> >> for the one, and 'Noto Sans CJK KR' for the other (both via the ftcr
    >> >> backend), and thereʼs no slowdown. (you can use C-u C-x = to check).
    >> 
    Andreas> Do you have many fonts installed?
    >> 
    >> fc-list | wc -l
    >> 2897

    Andreas> $ fc-list | wc -l
    Andreas> 11168

    Andreas> And there is a huge slowdown here.

Does it go away if you set font-backend . ftcrhb in your frame
parameters (assuming youʼre using Cairo)?

Robert