#25368: Update the Tor Rust coding standards for new types ----------------------------------------+---------------------------------- Reporter: teor | Owner: (none) Type: defect | Status: assigned Priority: Medium | Milestone: Tor: | 0.3.4.x-final Component: Core Tor/Tor | Version: Severity: Normal | Resolution: Keywords: doc, rust, review-group-34 | Actual Points: Parent ID: #23061 | Points: 0.5 Reviewer: isis | Sponsor: ----------------------------------------+---------------------------------- Changes (by teor):
* owner: teor => (none) * status: merge_ready => assigned Comment: Replying to [comment:5 isis]: > This looks great! A couple thoughts: > > 1) I only know enough about floating point arithmetic to stay away from it. That said, I was under the impression that [https://randomascii.wordpress.com/2012/02/25/comparing-floating-point- numbers-2012-edition/ different compilers (and/or different compiler flags) can treat bitwise-identical floating points differently], We can write unit tests for issues like this, but I don't think they will affect us. > and I worry in general that—if we allow `f{16,32,64}`s to cross the FFI boundary, that the C compiler on one side will treat them differently to how the Rust compiler does. I'm not sure how much this matters for the applications where we're using floating points, which seem mostly localised to the system using them "Raw transmutation from u64. This is currently identical to transmute::<u64, f64>(v) on all platforms. It turns out this is incredibly portable, for two reasons: Floats and Ints have the same endianess on all supported platforms. IEEE-754 very precisely specifies the bit layout of floats. However there is one caveat…" https://doc.rust-lang.org/std/primitive.f64.html#method.from_bits The caveat doesn't apply, because we aren't transmitting binary floats over the network. We don't even want to transmit decimal floats over the network. Nor would we ever transmit NaNs over the network. > (i.e. we're not sending floats over the network and expecting others to interpret them exactly as we do, right?). -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25368#comment:9> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online
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