Since this depends on the platform libm implementation of pow(), I'm closing this as "won't fix".

Steve, on the chance you're serious ;-) , there are implementations of the "constructive reals", which indeed act like infinite-precision floats.  But they tend to be very slow, and, e.g., testing two of them for equality is, in general, undecidable even in theory.  Here's one such:

https://www.chiark.greenend.org.uk/~sgtatham/spigot/