Debug printing a struct

[devout magnet]

How to print every field in a struct for debuging

found some code that said
inline for (std.meta.fields(@TypeOf(x))) |f| { std.log.debug(f.name ++ " {any}", .{@as(f.type, @field(x, f.name))}); }

[frosty condor]

zigs formatting does that by default so you can just pass it to a print function

std.debug.print("{}", .{your_struct});

[devout magnet]

this only prints what I assume is the internal mangled name of either the struct class or the struct instance

[frosty condor]

are you passing the struct type or an instance

it should print the fields

[devout magnet]

instance

[frosty condor]

show code

[devout magnet]

does this works even if the struct was declared in a .h?

[frosty condor]

it should

[devout magnet]

var application: c.VkPhysicalDevice = undefined; std.log.debug("full struct {?}", .{application});

and the output is

debug: full struct .<placeholder>.zig.zig-cache.o.11a0e6abe8f7d615c89001169bd5c984.cimport.struct_VkPhysicalDevice_T@aaaaaaaaaaaaaaaa

[gusty ore]

thats an opaque handle type, the fields aren't even specified

[devout magnet]

that makes lots of sense

[gusty ore]

its just a typedef struct VkPhysicalDevice_T* VkPhysicalDevice;

[devout magnet]

on that note, is = undefined the best way to 0 initialize a struct, seems kind of wrong to me lol

[gusty ore]

it does not zero-initialize, it leaves the memory uninitialized (= UB to access)

there is std.mem.zeroInit or std.mem.zeroes for that

but if possible the struct fields should just have a default value of zero and you can then initialize it with an empty literal, or by specifying only the fields you want to set

[frosty condor]

you wont be able to zero initialize an opaque type on the zig side

[devout magnet]

even with std.mem.zeroInit or std.mem.zeroes

?

[frosty condor]

zig has no knowledge of the fields so no

[gusty ore]

thats not necessary anyway, but its common to zero initialize the vulkan structs passed as arguments

[gusty ore]

you would create a null pointer, which is not allowed if the pointer type is not nullable

[frosty condor]

the pointer being null wouldnt make the struct null tho

[devout magnet]

but doesn't zig asume all c pointers are nullable?

[frosty condor]

i assume youre meant to pass it to some vulkan function for initialization

[gusty ore]

yes it does when using translate-c

[devout magnet]

structs are how vulkan handles you sending arguments to functions

[gusty ore]

but what exactly is the problem here? theres no reason to zero-init a VkPhysicalDevice, thats only ever an opaque handle to the device

[devout magnet]

it makes it convenient since some functions have docens of posible arguments

[gusty ore]

yes thats why I said this

[devout magnet]

I know, I only took a random struct from vulkan

ok, I will then change my question lol,

how am i supposed to zero initialize a struct?

[gusty ore]

best case this, or if not possible std.mem.zeroInit

when using https://github.com/Snektron/vulkan-zig all the relevant structs have default fields so the better approach works

[frosty condor]

translate-c structs are zero initialized by default now

[gusty ore]

oh really thats neat

[frosty condor]

so for non opaque types you can just do var foo: c.Bar = .{};

[devout magnet]

Okay

thats great

[gusty ore]

are you using translate-c to generate your own vulkan bindings?

[gusty ore]

because I'd strongly suggest using this, its great

[devout magnet]

okay, I will use it from now on

[devout magnet]

Do in need to update that individually?

[gusty ore]

what do you mean?

[devout magnet]

when I use translate-c it doesn't generate the code with the 0 defaults

[gusty ore]

then you probably don't have a recent enough compiler

[devout magnet]

isn't that feature on 0.11.0?

[frosty condor]

https://github.com/ziglang/zig/pull/17196