Minimal-dependencies implementation of bit_cast.

bit_cast.h

#include <string.h>

#if defined(__has_attribute)
#if __has_attribute(always_inline)
#define ALWAYS_INLINE __attribute__((always_inline))
#endif
#endif

#if defined(_MSC_VER)
// To reduce debug build overhead:
// Enable intrinsic memcpy: /Oi
// Enable force-inlining: /Ob1
#define ALWAYS_INLINE __forceinline
#endif

template <typename Dest, typename Source>
ALWAYS_INLINE Dest bit_cast(const Source& source)
{
    static_assert(sizeof(Dest) == sizeof(Source), "bit_cast to type of a different size");
    static_assert(__has_trivial_copy(Dest), "bit_cast to a type which is not trivially copyable");
    static_assert(__has_trivial_copy(Source), "bit_cast from a type which is not trivially copyable");

    // Note: could avoid calling constructor/destructor for Dest type, which is
    // what this proposed implementation (for C++20 standardization) does:
    // https://github.com/jfbastien/bit_cast/blob/master/bit_cast.h

    Dest dest;
    memcpy(&dest, &source, sizeof(dest));
    return dest;
}

// Example:
// https://godbolt.org/g/oqFZFH