// Copyright (c) 2014-2016 Khronos Group. This work is licensed under a
// Creative Commons Attribution 4.0 International License; see
// http://creativecommons.org/licenses/by/4.0/

vkGetInstanceProcAddr(3)
========================

Name
----
vkGetInstanceProcAddr - Return a function pointer for a command

C Specification
---------------

// refBegin vkGetInstanceProcAddr Return a function pointer for a command

Vulkan commands are not necessarily exposed statically on a platform.
Function pointers for all Vulkan commands can: be obtained with the
command:

include::../protos/vkGetInstanceProcAddr.txt[]


Parameters
----------

  * pname:instance is the instance that the function pointer will be
    compatible with.
  * pname:pName is the name of the command to obtain.


Description
-----------

fname:vkGetInstanceProcAddr itself is obtained in a platform- and loader-
specific manner. Typically, the loader library will export this command as a
function symbol, so applications can: link against the loader library, or
load it dynamically and look up the symbol using platform-specific APIs.
Loaders are encouraged to export function symbols for all other core
Vulkan commands as well; if this is done, then applications that use only
the core Vulkan commands have no need to use fname:vkGetInstanceProcAddr.

Function pointers to commands that do not operate on a specific instance can:
be obtained by using this command with pname:instance equal to `NULL`. The
following commands can: be accessed this way:

  * flink:vkEnumerateInstanceExtensionProperties
  * flink:vkEnumerateInstanceLayerProperties
  * flink:vkCreateInstance

The returned function pointer is of type tlink:PFN_vkVoidFunction, and must
be cast to the type of the command being queried.

If pname:instance is a valid sname:VkInstance, function pointers to any
commands that operate on pname:instance or a child of pname:instance can: be
obtained. The returned function pointer must: only be called with a
dispatchable object (the first parameter) that is a child of pname:instance.

If pname:pName is not the name of a core Vulkan command, or is an
extension command for any extension not supported by any available layer or
implementation, then fname:vkGetInstanceProcAddr will return `NULL`.

ifdef::editing-notes[]
[NOTE]
.editing-note
====
(Jon, Bug 14886 / Gitlab issue 4) The WSI group tentatively agreed that the
WSI extensions were special, and should get static entry points in link
libraries and prototypes in +vulkan.h+, while future extensions would have
to be dynamically loaded. If this decision is upheld by the group as a
whole, it would probably be encoded in the previous paragraph, in the WSI
extensions branch of the Specification.

However, this decision has not been fully signed off on by the entire Vulkan
WG yet AFAIK. Note that implementations typically will not support many of the
WSI extensions, so ``static entry points'' do not relieve apps of the
neccessity of runtime enabling and testing of each extension before using
it.
====
endif::editing-notes[]

include::../validity/protos/vkGetInstanceProcAddr.txt[]

// refEnd vkGetInstanceProcAddr PFN_vkVoidFunction


See Also
--------

tlink:PFN_vkVoidFunction, slink:VkInstance


Document Notes
--------------

For more information, see the Vulkan Specification at URL

https://www.khronos.org/registry/vulkan/specs/1.0/xhtml/vkspec.html#vkGetInstanceProcAddr

This page is extracted from the Vulkan Specification.
Fixes and changes should be made to the Specification,not directly.

include::footer.txt[]