Error: llroundl cannot be interpreted at compile time, because it has no available source code

[Stanislav Blinov]

On Monday, 8 June 2020 at 18:08:57 UTC, mw wrote:

> 2) even it does so, but why such simple function as lroundl 
> cannot be CTFE-ed?

Because, as the error message states, there's no source for it :) 
std.math calls into C math library.