This differs from scalbn in that the exponent has type long. When scaling an extended value, exponents slightly outside the range of int can actually be used meaningfully. We address this by doing multiple SCALBX calls (at most 2) in a loop.
Most of these actually just jump to the existing functions, since they really use extended precision anyway. The exception is the modf functions, which need a separate implementation for each type because they store a value through a pointer to that type.
The functions implemented so far are largely the ones that map (nearly) directly to SANE calls.
Note that C99 specifies separate float/double/long double versions of each of these functions, but under ORCA/C they generally use the same code.
These macros differ from the normal comparison operators in that they will not signal invalid due to the operands being unordered. However, this implementation will still signal invalid for SNaNs. That is clearly OK according to the wording in draft C23. C17 and earlier do not mention that possibility, but they do not really specify the behavior of SNaNs in general.