(__strtol, __strtol_t, __xstrtol): New macros to specify the underlying function, its returned type, and our function. Default to values suitable for xstrtol. Include <ctype.h>, since we use its macros. (ULONG_MAX, LONG_MAX, ISBLANK): Remove: no longer needed. (ISSPACE): New macro. (bkm_scale, bkm_scale_by_power, __xstrtol, main): __unsigned long int -> __strtol_t. (__xstrtol): Depend on whether __strtol_t is an unsigned type, not on whether STRING_TO_UNSIGNED is defined. Skip isspace chars, not isblank chars, to match strtol. When returning LONGINT_INVALID_SUFFIX_CHAR, store the value that we computed into *val.