[Archit3ch]

Slight correction, while the exponent is indeed fixed, it is larger than a f32/f64 exponent: https://gmplib.org/manual/Floating_002dpoint-Functions

However, this is not exposed in all GMP wrappers.

[seg_fault]

If I understand this correctly GMP has a flexible mantissa with no limitations during runtime.

In fas you have to specify the sizes (of mantissa and exponent) during compile time. So the size of this type is fixed. Thus, there is no heap involved.