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VK_EXT_debug_utils

Other Extension Metadata

Last Modified Date

2020-04-03

Revision

2

IP Status

No known IP claims.

Dependencies
  • This extension is written against version 1.0 of the Vulkan API.
  • Requires VkObjectType
Contributors
  • Mark Young, LunarG
  • Baldur Karlsson
  • Ian Elliott, Google
  • Courtney Goeltzenleuchter, Google
  • Karl Schultz, LunarG
  • Mark Lobodzinski, LunarG
  • Mike Schuchardt, LunarG
  • Jaakko Konttinen, AMD
  • Dan Ginsburg, Valve Software
  • Rolando Olivares, Epic Games
  • Dan Baker, Oxide Games
  • Kyle Spagnoli, NVIDIA
  • Jon Ashburn, LunarG
  • Piers Daniell, NVIDIA

Description

Due to the nature of the Vulkan interface, there is very little error information available to the developer and application. By using the VK_EXT_debug_utils extension, developers can obtain more information. When combined with validation layers, even more detailed feedback on the application’s use of Vulkan will be provided.

This extension provides the following capabilities:

  • The ability to create a debug messenger which will pass along debug messages to an application supplied callback.
  • The ability to identify specific Vulkan objects using a name or tag to improve tracking.
  • The ability to identify specific sections within a VkQueue or VkCommandBuffer using labels to aid organization and offline analysis in external tools.

The main difference between this extension and VK_EXT_debug_report and VK_EXT_debug_marker is that those extensions use VkDebugReportObjectTypeEXT to identify objects. This extension uses the core VkObjectType in place of VkDebugReportObjectTypeEXT. The primary reason for this move is that no future object type handle enumeration values will be added to VkDebugReportObjectTypeEXT since the creation of VkObjectType.

In addition, this extension combines the functionality of both VK_EXT_debug_report and VK_EXT_debug_marker by allowing object name and debug markers (now called labels) to be returned to the application’s callback function. This should assist in clarifying the details of a debug message including: what objects are involved and potentially which location within a VkQueue or VkCommandBuffer the message occurred.

New Object Types

New Commands

New Structures

New Function Pointers

New Enums

New Bitmasks

New Enum Constants

  • VK_EXT_DEBUG_UTILS_EXTENSION_NAME
  • VK_EXT_DEBUG_UTILS_SPEC_VERSION
  • Extending VkObjectType:
    • VK_OBJECT_TYPE_DEBUG_UTILS_MESSENGER_EXT
  • Extending VkStructureType:
    • VK_STRUCTURE_TYPE_DEBUG_UTILS_LABEL_EXT
    • VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CALLBACK_DATA_EXT
    • VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT
    • VK_STRUCTURE_TYPE_DEBUG_UTILS_OBJECT_NAME_INFO_EXT
    • VK_STRUCTURE_TYPE_DEBUG_UTILS_OBJECT_TAG_INFO_EXT

Examples

Example 1

VK_EXT_debug_utils allows an application to register multiple callbacks with any Vulkan component wishing to report debug information. Some callbacks may log the information to a file, others may cause a debug break point or other application-defined behavior. An application can register callbacks even when no validation layers are enabled, but they will only be called for loader and, if implemented, driver events.

To capture events that occur while creating or destroying an instance an application can link a VkDebugUtilsMessengerCreateInfoEXT structure to the pNext element of the VkInstanceCreateInfo structure given to vkCreateInstance.

Example uses: Create three callback objects. One will log errors and warnings to the debug console using Windows OutputDebugString. The second will cause the debugger to break at that callback when an error happens and the third will log warnings to stdout.

    extern VkInstance instance;
    VkResult res;
    VkDebugUtilsMessengerEXT cb1, cb2, cb3;

    // Must call extension functions through a function pointer:
    PFN_vkCreateDebugUtilsMessengerEXT pfnCreateDebugUtilsMessengerEXT = (PFN_vkCreateDebugUtilsMessengerEXT)vkGetInstanceProcAddr(instance, "vkCreateDebugUtilsMessengerEXT");
    PFN_vkDestroyDebugUtilsMessengerEXT pfnDestroyDebugUtilsMessengerEXT = (PFN_vkDestroyDebugUtilsMessengerEXT)vkGetInstanceProcAddr(instance, "vkDestroyDebugUtilsMessengerEXT");

    VkDebugUtilsMessengerCreateInfoEXT callback1 = {
        .sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT,
        .pNext = NULL,
        .flags = 0,
        .messageSeverity = VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT |
                           VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT,
        .messageType= VK_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT |
                      VK_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT,
        .pfnUserCallback = myOutputDebugString,
        .pUserData = NULL
    };
    res = pfnCreateDebugUtilsMessengerEXT(instance, &callback1, NULL, &cb1);
    if (res != VK_SUCCESS) {
       // Do error handling for VK_ERROR_OUT_OF_MEMORY
    }

    callback1.messageSeverity = VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT;
    callback1.pfnUserCallback = myDebugBreak;
    callback1.pUserData = NULL;
    res = pfnCreateDebugUtilsMessengerEXT(instance, &callback1, NULL, &cb2);
    if (res != VK_SUCCESS) {
       // Do error handling for VK_ERROR_OUT_OF_MEMORY
    }

    VkDebugUtilsMessengerCreateInfoEXT callback3 = {
        .sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT,
        .pNext = NULL,
        .flags = 0,
        .messageSeverity = VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT,
        .messageType = VK_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT |
                       VK_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT,
        .pfnUserCallback = mystdOutLogger,
        .pUserData = NULL
    };
    res = pfnCreateDebugUtilsMessengerEXT(instance, &callback3, NULL, &cb3);
    if (res != VK_SUCCESS) {
       // Do error handling for VK_ERROR_OUT_OF_MEMORY
    }

    ...

    // Remove callbacks when cleaning up
    pfnDestroyDebugUtilsMessengerEXT(instance, cb1, NULL);
    pfnDestroyDebugUtilsMessengerEXT(instance, cb2, NULL);
    pfnDestroyDebugUtilsMessengerEXT(instance, cb3, NULL);

Example 2

Associate a name with an image, for easier debugging in external tools or with validation layers that can print a friendly name when referring to objects in error messages.

    extern VkInstance instance;
    extern VkDevice device;
    extern VkImage image;

    // Must call extension functions through a function pointer:
    PFN_vkSetDebugUtilsObjectNameEXT pfnSetDebugUtilsObjectNameEXT = (PFN_vkSetDebugUtilsObjectNameEXT)vkGetInstanceProcAddr(instance, "vkSetDebugUtilsObjectNameEXT");

    // Set a name on the image
    const VkDebugUtilsObjectNameInfoEXT imageNameInfo =
    {
        .sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_OBJECT_NAME_INFO_EXT,
        .pNext = NULL,
        .objectType = VK_OBJECT_TYPE_IMAGE,
        .objectHandle = (uint64_t)image,
        .pObjectName = "Brick Diffuse Texture",
    };

    pfnSetDebugUtilsObjectNameEXT(device, &imageNameInfo);

    // A subsequent error might print:
    //   Image 'Brick Diffuse Texture' (0xc0dec0dedeadbeef) is used in a
    //   command buffer with no memory bound to it.

Example 3

Annotating regions of a workload with naming information so that offline analysis tools can display a more usable visualization of the commands submitted.

    extern VkInstance instance;
    extern VkCommandBuffer commandBuffer;

    // Must call extension functions through a function pointer:
    PFN_vkQueueBeginDebugUtilsLabelEXT pfnQueueBeginDebugUtilsLabelEXT = (PFN_vkQueueBeginDebugUtilsLabelEXT)vkGetInstanceProcAddr(instance, "vkQueueBeginDebugUtilsLabelEXT");
    PFN_vkQueueEndDebugUtilsLabelEXT pfnQueueEndDebugUtilsLabelEXT = (PFN_vkQueueEndDebugUtilsLabelEXT)vkGetInstanceProcAddr(instance, "vkQueueEndDebugUtilsLabelEXT");
    PFN_vkCmdBeginDebugUtilsLabelEXT pfnCmdBeginDebugUtilsLabelEXT = (PFN_vkCmdBeginDebugUtilsLabelEXT)vkGetInstanceProcAddr(instance, "vkCmdBeginDebugUtilsLabelEXT");
    PFN_vkCmdEndDebugUtilsLabelEXT pfnCmdEndDebugUtilsLabelEXT = (PFN_vkCmdEndDebugUtilsLabelEXT)vkGetInstanceProcAddr(instance, "vkCmdEndDebugUtilsLabelEXT");
    PFN_vkCmdInsertDebugUtilsLabelEXT pfnCmdInsertDebugUtilsLabelEXT = (PFN_vkCmdInsertDebugUtilsLabelEXT)vkGetInstanceProcAddr(instance, "vkCmdInsertDebugUtilsLabelEXT");

    // Describe the area being rendered
    const VkDebugUtilsLabelEXT houseLabel =
    {
        .sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_LABEL_EXT,
        .pNext = NULL,
        .pLabelName = "Brick House",
        .color = { 1.0f, 0.0f, 0.0f, 1.0f },
    };

    // Start an annotated group of calls under the 'Brick House' name
    pfnCmdBeginDebugUtilsLabelEXT(commandBuffer, &houseLabel);
    {
        // A mutable structure for each part being rendered
        VkDebugUtilsLabelEXT housePartLabel =
        {
            .sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_LABEL_EXT,
            .pNext = NULL,
            .pLabelName = NULL,
            .color = { 0.0f, 0.0f, 0.0f, 0.0f },
        };

        // Set the name and insert the marker
        housePartLabel.pLabelName = "Walls";
        pfnCmdInsertDebugUtilsLabelEXT(commandBuffer, &housePartLabel);

        // Insert the drawcall for the walls
        vkCmdDrawIndexed(commandBuffer, 1000, 1, 0, 0, 0);

        // Insert a recursive region for two sets of windows
        housePartLabel.pLabelName = "Windows";
        pfnCmdBeginDebugUtilsLabelEXT(commandBuffer, &housePartLabel);
        {
            vkCmdDrawIndexed(commandBuffer, 75, 6, 1000, 0, 0);
            vkCmdDrawIndexed(commandBuffer, 100, 2, 1450, 0, 0);
        }
        pfnCmdEndDebugUtilsLabelEXT(commandBuffer);

        housePartLabel.pLabelName = "Front Door";
        pfnCmdInsertDebugUtilsLabelEXT(commandBuffer, &housePartLabel);

        vkCmdDrawIndexed(commandBuffer, 350, 1, 1650, 0, 0);

        housePartLabel.pLabelName = "Roof";
        pfnCmdInsertDebugUtilsLabelEXT(commandBuffer, &housePartLabel);

        vkCmdDrawIndexed(commandBuffer, 500, 1, 2000, 0, 0);
    }
    // End the house annotation started above
    pfnCmdEndDebugUtilsLabelEXT(commandBuffer);

    // Do other work

    vkEndCommandBuffer(commandBuffer);

    // Describe the queue being used
    const VkDebugUtilsLabelEXT queueLabel =
    {
        .sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_LABEL_EXT,
        .pNext = NULL,
        .pLabelName = "Main Render Work",
        .color = { 0.0f, 1.0f, 0.0f, 1.0f },
    };

    // Identify the queue label region
    pfnQueueBeginDebugUtilsLabelEXT(queue, &queueLabel);

    // Submit the work for the main render thread
    const VkCommandBuffer cmd_bufs[] = {commandBuffer};
    VkSubmitInfo submit_info =
    {
        .sType = VK_STRUCTURE_TYPE_SUBMIT_INFO,
        .pNext = NULL,
        .waitSemaphoreCount = 0,
        .pWaitSemaphores = NULL,
        .pWaitDstStageMask = NULL,
        .commandBufferCount = 1,
        .pCommandBuffers = cmd_bufs,
        .signalSemaphoreCount = 0,
        .pSignalSemaphores = NULL
    };
    vkQueueSubmit(queue, 1, &submit_info, fence);

    // End the queue label region
    pfnQueueEndDebugUtilsLabelEXT(queue);

Issues

1) Should we just name this extension VK_EXT_debug_report2

RESOLVED: No. There is enough additional changes to the structures to break backwards compatibility. So, a new name was decided that would not indicate any interaction with the previous extension.

2) Will validation layers immediately support all the new features.

RESOLVED: Not immediately. As one can imagine, there is a lot of work involved with converting the validation layer logging over to the new functionality. Basic logging, as seen in the origin VK_EXT_debug_report extension will be made available immediately. However, adding the labels and object names will take time. Since the priority for Khronos at this time is to continue focusing on Valid Usage statements, it may take a while before the new functionality is fully exposed.

3) If the validation layers will not expose the new functionality immediately, then what is the point of this extension?

RESOLVED: We needed a replacement for VK_EXT_debug_report because the VkDebugReportObjectTypeEXT enumeration will no longer be updated and any new objects will need to be debugged using the new functionality provided by this extension.

4) Should this extension be split into two separate parts (1 extension that is an instance extension providing the callback functionality, and another device extension providing the general debug marker and annotation functionality)?

RESOLVED: No, the functionality for this extension is too closely related. If we did split up the extension, where would the structures and enums live, and how would you define that the device behavior in the instance extension is really only valid if the device extension is enabled, and the functionality is passed in. It is cleaner to just define this all as an instance extension, plus it allows the application to enable all debug functionality provided with one enable string during vkCreateInstance.

Version History

  • Revision 1, 2017-09-14 (Mark Young and all listed Contributors)
  • Revision 2, 2020-04-03 (Mark Young and Piers Daniell)
    • Updated to allow either NULL or an empty string to be passed in for pObjectName in VkDebugUtilsObjectNameInfoEXT, because the loader and various drivers support NULL already.