If I understand it correctly, it basically boils down to copying bits from the source to the destination, in order from the least significant bit to the most significant bit. It's not equivalent to C++'s reinterpret_cast.

I'm no Zig expert, but if you want endian-dependent semantics I'd assume either @ptrCast or a packed union would do the job.

▲ tremon 2 hours ago | parent [-]

But doesn't that show why this is a bad idea? If I understand correctly, this code:

  const MyUnion = packed union {
    full: u16,
    bytes: [2]u8,
  };
  const value: u16 = 0x55aa;
  const in_union: MyUnion = @bitCast(value);
  const without_union: [2]u8 = @bitCast(value);
  std.debug.assert(without_union[0] == in_union.bytes[0]);
  std.debug.assert(without_union[1] == in_union.bytes[1]);

...will now succeed or fail depending on the endianness of the target. That looks like the type of footgun that will bring decades of joy.

▲

peesem an hour ago | parent | next [-]

zig does not allow arrays in packed structs/unions specifically for endianness reasons (there may be other reasons as well but endianness is what i know of)

▲

AlienRobot an hour ago | parent | prev [-]

I wonder if packed union also got/will get the same "logical bits" treatment?

	▲	SkiFire13 2 minutes ago \| parent [-]
		My understanding is that the "logical bits" view breaks down for unions, because the nth logical bit could be at different offsets depending on the union variant that's considered active.