...

That line number doesn't seem to match with either of the two precompile.pike files in recent Pike 7.8. Can you give an excerpt?

Sure... it's:

[...]

          ret+=({
            PC.Token(sprintf("if(Pike_sp[%d%s].type !=  

PIKE_T_STRING || Pike_sp[%d%s].ustring -> width)", argnum,check_argbase, argnum,check_argbase, upper_case(arg->basetype())),arg-

...

line())

          });

Ok, that seems to correspond to line ~2211 in Pike 7.8, where it has been fixed by removing the last argument to the sprintf.