Crash after destroying a couple of SwapchainKHR instances :/

[hcabel]

Hey I'm pretty new to ash and while I was trying to create multiple swapchain to support multiple window I realize that sometime I get a STATUS_ACCESS_VIOLATION or a HEAP_CORRUPTION... crash when calling the destroy_swapchain function of the swapchain loader :/
So I though it might be because I create a swapchain loader per swapchain instance, but even after moving the loader to my vulkan_context structure the crash is still occurring.
here is some code:

pub(super)
struct Swapchain
{
	vulkan_context: Weak<VulkanContext>,
	raw: vk::SwapchainKHR,
	frames: Vec<Frame>,
}

impl Swapchain
{
	pub(super)
	fn new(vulkan_context: &Rc<VulkanContext>, sizes: &[f32; 2]) -> Self
	{
		win_render_log!(Verbose, "Creating swapchain...");

		let surface_format = choose_surface_format(
			vulkan_context,
			vk::Format::B8G8R8A8_SRGB,
			vk::ColorSpaceKHR::SRGB_NONLINEAR,
		);
		let present_mode = choose_present_mode(
			vulkan_context,
			vk::PresentModeKHR::MAILBOX,
		);
		let extent = choose_extent(
			vulkan_context,
			sizes
		);
		let image_count = choose_image_count(
			vulkan_context,
			3,
		);

		let unique_queue_family_indices =
			vulkan_context.queue_family_indices
				.get_unique_values()
				.iter()
				.map(|&index| index as u32)
				.collect::<Vec<u32>>();
		let sharing_mode = {
			if unique_queue_family_indices.len() == 1 {
				vk::SharingMode::EXCLUSIVE
			} else {
				vk::SharingMode::CONCURRENT
			}
		};

		let create_info = vk::SwapchainCreateInfoKHR::builder()
			.surface(vulkan_context.surface.handle)
			.min_image_count(image_count)
			.image_format(surface_format.format)
			.image_color_space(surface_format.color_space)
			.image_extent(extent)
			.image_array_layers(1)
			.image_usage(vk::ImageUsageFlags::COLOR_ATTACHMENT)
			.image_sharing_mode(sharing_mode)
			.queue_family_indices(&unique_queue_family_indices)
			.pre_transform(vk::SurfaceTransformFlagsKHR::IDENTITY)
			.present_mode(present_mode)
			.composite_alpha(vk::CompositeAlphaFlagsKHR::OPAQUE);


		win_render_log!(Verbose, "Format: \"{:?}\" \"{:?}\"",
			surface_format.format,
			surface_format.color_space
		);
		win_render_log!(Verbose, "Present mode: \"{:?}\"", present_mode);
		win_render_log!(Verbose, "Extent: {}x{}", extent.width, extent.height);
		win_render_log!(Verbose, "Image count: {}", image_count);

		let swapchain = unsafe {
			vulkan_context.swapchain_loader.create_swapchain(&create_info, None)
				.expect("Unable to create swapchain")
		};

		let swapchain_images = unsafe {
			vulkan_context.swapchain_loader.get_swapchain_images(swapchain)
				.expect("Unable to get swapchain images")
		};

		let frames =
			swapchain_images.iter().map(|&image| {
				Frame::new(
					vulkan_context,
					&image,
					surface_format.format,
					extent,
				)
			}).collect::<Vec<_>>();

		Self {
			vulkan_context: Rc::downgrade(vulkan_context),
			raw: swapchain,
			frames,
		}
	}
}


impl Drop for Swapchain
{
	fn drop(&mut self)
	{
		win_render_log!(Verbose, "Dropping swapchain...");

		let vulkan_context = {
			let rc = self.vulkan_context.upgrade();
			if rc.is_none() {
				win_render_log!(Error, "Swapchain cleanup failed! Vulkan context is dropped!");
				return;
			}
			rc.unwrap()
		};

		self.frames.clear();

		unsafe {
			vulkan_context.swapchain_loader.destroy_swapchain(self.raw, None);
		}
	}
}

nothing fency, creating a swapchain then calling the delete function when Dropped.

Before you ask:

• it's indeed dropped prior to the device/instance.
• The frame doesn't contain anything yet it's literally an empty struct

(edit): I've made a very simple program that trigger this crash down the comment

Thanks for your time :)

[Ralith]

Did you keep your Entry object around? Do the validation layers have anything to say?

[hcabel]

@Friz64 Thanks for your suggestion, sadly it does not fix the issue. (Yeah this code example is very rough 😆)
Try multiple time this crash doesn't happened all the time (~75%) creating more window will crash more often too.

Thanks for the .build() tips I wasn't aware of that, thanks ❤️

[MarijnS95]

Maybe run the code through rustmft, that should make it less rough :)

Per the readme, as quoted by @Friz64, you should almost never (have to) call .build() and it's a massive footgun at that. That's why it will be removed in the next release.

If you remove it, the Rust compiler will automatically tell you where your pointers (now lifetimed borrows!) are pointing to stale and dropped structures.

Few random notes:

1. don't use the +metadata part in crate dependencies' versions. This is only informational when the crate is published and won't be used to select an alternative crate version;
2. [[bin]] name = "<package name>" is not required for src/main.rs;
3. Calling .unwrap() is nicer outside the unsafe {} block, and puts some statements on a single line again;
4. Use CStr::from_bytes_with_nul(b"No engine\0") and friends (in a future Rust version c"No engine"!) to create 'static lifetimed strings that aren't deallocated;
5. Create surfaces in winit::Event...::Resumed and destroy them in ::Suspended to support mobile platforms;
6. Use our ash-window crate to take care of turning a RawWindowHandle into a surface.

[hcabel]

Thanks I appreciated those notes, I'll keep them in mind 👍
For the crash itself I can't find a way to resolve it, I've spend the last couple of hours trying to avoid any drop of any variable to see if it fix the issue but it doesn't... (based on the "fixed" version that Friz64 provided), but the crash still occur. I'm sorry if it's obvious and I'm missing it but I don't see which variable is being dropped and trigger the crash.
I might try to build Vulkan locally with the symbol later (hopefully the debugger will show something more than the assembly)

[Friz64]

FWIW, I have run my "fixed" version dozens of times and it didn't crash a single time. This testing was done on Windows 11, latest AMD drivers, latest Vulkan SDK. You could maybe try your luck in other Vulkan communities, such as the Vulkan Discord: https://discord.com/invite/vulkan