wip2

wgpu-hal/src/vulkan/adapter.rs

@@ -342,13 +342,6 @@ impl PhysicalDeviceFeatures {
                 None
             },
             robustness2: if enabled_extensions.contains(&ext::robustness2::NAME) {
-                // Ordinary `robust_buffer_access`, as provided by Vulkan 1.0
-                // without extensions, is not sufficient to meet WebGPU's
-                // requirements: it only promises that
-                //
-                // Note: enabling `robust_buffer_access2` isn't required, strictly speaking
-                // since we can enable `robust_buffer_access` all the time. But it improves
-                // program portability, so we opt into it if they are supported.
                 Some(
                     vk::PhysicalDeviceRobustness2FeaturesEXT::default()
                         .robust_buffer_access2(private_caps.robust_buffer_access2)

wgpu-hal/src/vulkan/mod.rs

@@ -493,8 +493,27 @@ struct PrivateCapabilities {
     /// Ability to present contents to any screen. Only needed to work around broken platform configurations.
     can_present: bool,
     non_coherent_map_mask: wgt::BufferAddress,
+
+    /// True if this adapter advertises the [`robustBufferAccess`][vrba] feature.
+    ///
+    /// Note that `robustBufferAccess` *would* suffice to meet WebGPU's
+    /// requirements for out-of-bounds accesses, but not if `wgpu-core` uses
+    /// deferred buffer initialization.
+    ///
+    /// Vulkan and WebGPU agree on the definition of out-of-bounds access, and
+    /// enabling `robustBufferAccess` ensures that out-of-bounds accesses will,
+    /// at worst, read other contents from the same buffer. However, 
+    ///
+    /// [vrba]: https://registry.khronos.org/vulkan/specs/1.3-extensions/html/vkspec.html#features-robustBufferAccess
     robust_buffer_access: bool,
     robust_image_access: bool,
+    // Ordinary `robust_buffer_access`, as provided by Vulkan 1.0
+    // without extensions, is sufficient to meet WebGPU's
+    // requirements, but not sufficient
+    //
+    // Note: enabling `robust_buffer_access2` isn't required, strictly speaking
+    // since we can enable `robust_buffer_access` all the time. But it improves
+    // program portability, so we opt into it if they are supported.
     robust_buffer_access2: bool,
     robust_image_access2: bool,
     zero_initialize_workgroup_memory: bool,