PNEXT

pNext is a convention used in the Vulkan API to allow extending core structures with optional, vendor-specific, or future features without changing the core definitions. It is a member named pNext that appears in many Vulkan structures and serves as a pointer to a linked list of additional structures.

The primary purpose of pNext is to enable structure chaining. Each structure that participates in a chain begins with a known header, typically including a structure type identifier (sType) and a pNext pointer. The pNext field can point to another extension structure, which itself starts with an sType and its own pNext, forming a chain. Real-world usage involves populating the base structure’s sType, setting pNext to point to the first extension structure, and filling the extension’s fields as required by the target feature or extension.

Usage examples include augmenting create info or feature queries with extension structures. For instance, a base VkInstanceCreateInfo can be extended by attaching VkValidationFeaturesEXT or VkDebugUtilsMessengerCreateInfoEXT through its pNext chain, allowing drivers to interpret and apply additional settings without altering the core API surface. Similar chaining occurs with features and capabilities in other Vulkan structures, such as VkPhysicalDeviceFeatures2 and related feature structures.

Important considerations include ensuring correct sType values for each chained structure, maintaining a valid, NULL-terminated chain, and respecting extension availability on the target platform or driver. The pNext mechanism is central to Vulkan’s modular, extensible design and is widely used across its ecosystem. See also Vulkan API, VkStructureType, and VkBaseInStructure/VkBaseOutStructure.