Double-check C bitfield translation

[ianprime0509]

I'm no longer sure I trust the prior understanding of bitfields that caused me to write this:

zig-gobject/src/translate.zig

Lines 739 to 781 in 4ee2c0d

	fn translateLinearFields(allocator: Allocator, fields: []const gir.Field, ctx: TranslationContext, out: anytype) !void {
	// The handling of bit fields aligns with what a "normal" C compiler should
	// do: pack adjacent bit fields next to each other, padding out to the next
	// byte after the last bit field in a sequence. This is not guaranteed by
	// the standard, but GObject stuff seems to assume it.
	var in_bit_fields = false;
	var bit_fields_bits: u16 = 0;
	var n_bit_fields: usize = 0;
	for (fields) |field| {
	if (field.bits) |bits| {
	if (!in_bit_fields) {
	try out.print("bitfields$L: packed struct ${\n", .{n_bit_fields});
	in_bit_fields = true;
	}
	try out.print("$I: u$L,\n", .{ field.name, bits });
	bit_fields_bits += bits;
	} else {
	if (in_bit_fields) {
	const total_bits = @max(math.ceilPowerOfTwoPromote(u16, bit_fields_bits), 8);
	const padding_bits = total_bits - bit_fields_bits;
	if (padding_bits > 0) {
	try out.print("padding: u$L,\n", .{padding_bits});
	}
	try out.print("$},\n", .{});
	in_bit_fields = false;
	bit_fields_bits = 0;
	n_bit_fields += 1;
	}
	try out.print("$I: ", .{field.name});
	try translateFieldType(allocator, field.type, ctx, out);
	try out.print(",\n", .{});
	}
	}
	// Handle trailing bit fields
	if (in_bit_fields) {
	const total_bits = @max(math.ceilPowerOfTwoPromote(u16, bit_fields_bits), 8);
	const padding_bits = total_bits - bit_fields_bits;
	if (padding_bits > 0) {
	try out.print("padding: u$L,\n", .{padding_bits});
	}
	try out.print("$},\n", .{});
	}
	}

It seems to be more complicated than I previously understood.

Related: ziglang/zig#1499 There is a project in the comments of that issue that might help solidify the translation in this library.