Comment 1 for bug 1777788

I can confirm that this also affects Xubuntu 18.04 with tcl/tk 8.5. This ran apparently successfully:

./configure --prefix=/home/me --with-tclconfig=/usr/lib/tcl8.5 --with-tkconfig=/usr/lib/tk8.5 CPPFLAGS=-I/usr/include/tcl8.5

However, the subsequent make fails:

main.C: In function ‘int Ical_Init(Tcl_Interp*)’:
main.C:147:65: error: invalid conversion from ‘unsigned char*’ to ‘const char*’ [-fpermissive]
 (Tk_DefineBitmap(tcl,Tk_GetUid(id),n##_bits,n##_width,n##_height) == TCL_OK)
                                                                 ^
main.C:154:14: note: in expansion of macro ‘MAKE_BITMAP’
         if (!MAKE_BITMAP(tcl, "left_arrow", left)) return TCL_ERROR;
              ^~~~~~~~~~~
In file included from /usr/include/tcl8.5/tk.h:1537:0,
                 from main.C:24:
...