numpy_quaddtype.get_sleef_constant("smallest_subnormal")

returns QuadPrecision('3.362103143112093506262677817321753e-4932', backend='sleef'), which does not match the documented 2^-16494 from https://sleef.org/quad.xhtml.

The implementation here

https://github.com/numpy/numpy-user-dtypes/blob/47c94090a52321b6116fe29382d16e866c0ae939/quaddtype/numpy_quaddtype/src/quaddtype_main.c#L73-L75

looks correct, is the macro defined in the wrong way?

In any case, we should fix this and add tests for all exposed constant values.