William Xu writes: > I need to make below additional change, otherwise it works perfectly. Incorporated in the attached final version of the patch. > Looking at the changes, I see you changed below `concat' call to > `format'. Is this in the end some bug in the `concat' implementation? It is complex. I am not sure if it is a bug or just some obscure implementation detail. See Emacs bug#48740 https://debbugs.gnu.org/cgi/bugreport.cgi?bug=48740 Best, Ihor