# Field defaults in vulkan-zig

**URL:** <https://ziggit.dev/t/field-defaults-in-vulkan-zig/17413>\
**Category:** Help\
**Tags:** vulkan\
**Created:** [August 29, 2026, 2:11pm UTC](https://ziggit.dev/t/field-defaults-in-vulkan-zig/17413 "2026-08-29T14:11:43Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![dpirch](https://ziggit.dev/user_avatar/ziggit.dev/dpirch/32/5321_2.png) [@dpirch](https://ziggit.dev/u/dpirch)\
**Post date:** [August 29, 2026, 2:11pm UTC](https://ziggit.dev/t/field-defaults-in-vulkan-zig/17413/1 "2026-08-29T14:11:43Z")

</div>

I started using Snektron/vulkan-zig for Vulkan again, but what I find very cumbersome is that most of the struct fields don’t have default values, and you have to set lots of nonsensical values that in C would be set implicitly through default initialization, for example

```zig
const depth_stencil_state = vk.PipelineDepthStencilStateCreateInfo{
    .depth_test_enable = .true,
    .depth_write_enable = .true,
    .depth_compare_op = .less_or_equal,
    .depth_bounds_test_enable = .false,
    .stencil_test_enable = .false,
    .front = .{
        .fail_op = .keep,
        .pass_op = .keep,
        .compare_op = .never,
        .compare_mask = 0,
        .depth_fail_op = .keep,
        .reference = 0,
        .write_mask = 0,
    },
    .back = .{
        .write_mask = 0,
        .compare_mask = 0,
        .compare_op = .never,
        .depth_fail_op = .keep,
        .fail_op = .keep,
        .pass_op = .keep,
        .reference = 0,
    },
    .max_depth_bounds = 0,
    .min_depth_bounds = 0,
};

```

Everything after the first 5 fields is completely meaningless noise; it is just the configuration for things that are already disabled. And this is needed with a lot of structs; I guess the whole Vulkan API was designed with default initialization in mind, with 0 values and 0 enum constants as defaults when not using some feature.

Is there some way around this, what do people do in practice when using these bindings?

Is there some reason why vulkan-zig doesn’t just generate default values for all the struct fields that match C default initialization?

---

<div class="post-metadata">

**Author:** ![rpkak](https://ziggit.dev/letter_avatar_proxy/v4/letter/r/a4c791/32.png) [@rpkak](https://ziggit.dev/u/rpkak)\
**Post date:** [August 29, 2026, 3:21pm UTC](https://ziggit.dev/t/field-defaults-in-vulkan-zig/17413/2 "2026-08-29T15:21:10Z")

</div>

If vulkan-zig generates default values or not, [depends](https://github.com/Snektron/vulkan-zig/blob/a6ca07453ba82e6fbdd910c2e364ae3ee77d7f81/src/vulkan/render.zig#L1174-L1194) on the `optional` field of the `vk.xml`.

[Docs of the `optional` field](https://registry.khronos.org/vulkan/specs/latest/registry.html#_attributes_of_member_tags):

> Must be `"true"` or `"false"` . The default value if unspecified is `"false"` . `"true"` specifies that this member can contain a sentinel value indicating that no corresponding object or explicit value is referred to: `NULL` for pointers, `VK_NULL_HANDLE` for handles, or 0 for other scalar types. `"false"` specifies that the member must contain a value object reference or explicit value.

IMO it makes sense, that no default value is generated, if no `optional="true"` is present.

---

<div class="post-metadata">

**Author:** ![dpirch](https://ziggit.dev/user_avatar/ziggit.dev/dpirch/32/5321_2.png) [@dpirch](https://ziggit.dev/u/dpirch)\
**Post date:** [August 29, 2026, 4:36pm UTC](https://ziggit.dev/t/field-defaults-in-vulkan-zig/17413/3 "2026-08-29T16:36:40Z")

</div>

But the Vulkan registry, fields generally only have this “optional” flag if they are themselves needed to indicate that something is disabled or not present (with a null handle, null pointer, zero count), not if they are just meaningless/ignored depending on some other field. Is doesn’t really make sense to me that vulkan-zig uses this for generating defaults.

---

<div class="post-metadata">

**Author:** ![Cloudef](https://ziggit.dev/user_avatar/ziggit.dev/cloudef/32/1370_2.png) [@Cloudef](https://ziggit.dev/u/Cloudef)\
**Post date:** [August 29, 2026, 4:48pm UTC](https://ziggit.dev/t/field-defaults-in-vulkan-zig/17413/4 "2026-08-29T16:48:40Z")

</div>

Ideally there would be some manual touchups so things could have decl literals like `pub const off = std.mem.zeroes(@This());` or even methods that initialize part of the structs without making partial init programming errors.

Anyhow, you can do:

```zig
var depth_stencil_state = std.mem.zeroInit(vk.PipelineDepthStencilStateCreateInfo, .{
    .depth_test_enable = .true,
    .depth_write_enable = .true,
    .depth_compare_op = .less_or_equal,
    .depth_bounds_test_enable = .false,
    .stencil_test_enable = .false,
});

```