martinmoene / byte-lite Goto Github PK

Hi, byte-lite appears to fail the tests in a big-endian configuration.
For context, it was an automated build having the s390x architecture enabled.

/builddir/build/BUILD/byte-lite-0.3.0/test/byte.t.cpp:193: failed:
byte: Allows strict aliasing: 14 == F::f( i, reinterpret_cast<nonstd::byte&>( i ) ) for 14 == 7

builder-live.log.gz

What's the advantage of this over enum class byte : std::uint8_t {}; or using byte = uint8_t?

As Richard Smith points out in https://groups.google.com/a/isocpp.org/d/msg/std-proposals/McSXSFki08I/fwKKfZqNCAAJ, your byte implementation would be unsafe under strict aliasing optimisation.

The solution is to mark up your byte type with __attribute__((__may_alias__)) on GCC and clang, For MSVC, currently, unless you use __declspec(noalias) and/or __declspec(restrict), everything is assumed to alias, though Microsoft promise that strict aliasing optimisation is coming at some point soon.