Wrong size of packed struct with bit flags

[michal-z]

I have defined below packed struct. There are 14 'bool' fields and u18 padding field. I was expecting @sizeof(RESOURCE_STATES) to be 4. Unfortunately @sizeof(RESOURCE_STATES) is 5.

pub const RESOURCE_STATES = packed struct {
    VERTEX_AND_CONSTANT_BUFFER: bool = false,
    INDEX_BUFFER: bool = false,
    RENDER_TARGET: bool = false,
    UNORDERED_ACCESS: bool = false,
    DEPTH_WRITE: bool = false,
    DEPTH_READ: bool = false,
    NON_PIXEL_SHADER_RESOURCE: bool = false,
    PIXEL_SHADER_RESOURCE: bool = false,
    STREAM_OUT: bool = false,
    INDIRECT_ARGUMENT_AND_PREDICATION: bool = false,
    COPY_DEST: bool = false,
    COPY_SOURCE: bool = false,
    RESOLVE_DEST: bool = false,
    RESOLVE_SOURCE: bool = false,

    padding: u18 = 0,
};

The same technique but for smaller structs works as expected:

pub const HEAP_FLAGS = packed struct {
    SHARED: bool = false,
    DENY_BUFFERS: bool = false,
    ALLOW_DISPLAY: bool = false,
    SHARED_CROSS_ADAPTER: bool = false,
    DENY_RT_DS_TEXTURES: bool = false,
    DENY_NON_RT_DS_TEXTURES: bool = false,
    HARDWARE_PROTECTED: bool = false,

    padding: u25 = 0,
};

@sizeof(HEAP_FLAGS) == 4.

As a workaround I have to define 18 'bool' padding fields in RESOURCE_STATES struct.

Thanks,
Michal

[pfgithub]

Packed structs are currently a bit broken unfortunately. The issues to watch about this are #2627 and #3133

[Vexu]

Fixed in self-hosted.