From line_map comment at (libcpp/include/line-map.h)
/* Physical source file TO_FILE at line TO_LINE at column 0 is represented
by the logical START_LOCATION. TO_LINE+L at column C is represented by
START_LOCATION+(L*(1<<column_bits))+C, as long as C< (1<<column_bits),
What happens when column number is >= 128 ? This is PR 20907.
What should happen? Well, col==0 would be reasonable.
