- that is, a string (not) terminating with a slash.

That is, very large integers *with* the suffix specified.
It was unconditionally converting the value to uint64, but have to check for the validity of that first.
Additional check for num_size < 20 fixes it. Such numbers definitely fit into uint64. And this condition fully covers int64, too. gen_check_uint_fits_in_size is not used for uint64 so this is fine.

Parsing/stringifying a macro body would always add two spaces and a newline, but it's supposed to stop changing after one pass.