E.4. Platform-Specific Macro Definitions in vk_platform.h

## E.4. Platform-Specific Macro Definitions in `vk_platform.h`

In addition to the macros described for `vulkan.h`, platform-specific macros specified and used in the included `vk_platform.h` file are described in this section. These macros are specifically used to control platform-dependent behavior and their exact definitions are under the control of specific platforms and Vulkan implementations.

### E.4.1. Platform-Specific Calling Conventions

`VKAPI_ATTR` is a macro placed before the return type in Vulkan API function declarations. If not empty, the interpretation of this macro depends on the platform and compiler in use, but normally controls calling conventions for C++11 and GCC/Clang-style compilers.

`VKAPI_CALL` is a macro placed after the return type in Vulkan API function declarations. If not empty, the interpretation of this macro depends on the platform and compiler in use, but normally controls calling conventions for MSVC-style compilers.

`VKAPI_PTR` is a macro placed between the ( and * in Vulkan API function pointer declarations. If not empty, the interpretation of this macro depends on the platform and compiler in use, and normally controls calling conventions. `VKAPI_PTR` typically has the same definition as `VKAPI_ATTR` or `VKAPI_CALL`, depending on the compiler.

### E.4.2. Platform-Specific Header Control

If the `VK_NO_STDINT_H` macro is defined by the application at compile time, extended integer types required by `vulkan.h`, such as `uint8_t`, must also be defined by the application. Otherwise, `vulkan.h` will not compile. If `VK_NO_STDINT_H` is not defined, the system `<stdint.h>` is used to define these types, or there is a fallback path when Microsoft Visual Studio version 2008 and earlier versions are detected at compile time.

### E.4.3. Window System-Specific Header Control

When using different window systems with Khronos extensions, header files for those window systems must be included at compile time in order for the corresponding extension definitions to compile. The Vulkan header files cannot determine whether or not an external header is available at compile time, so applications must include macros enabling those headers. If this is not done, the corresponding extension interfaces will not be defined and they will be unusable.

The extensions, required compile-time symbols to enable them, and window systems they correspond to are defined in the following table.

Table E.1. Window System Extensions and Required Compile-Time Symbol Definitions

Extension Name | Required Compile-Time Symbol | Window System Name
--- | --- | ---
`VK_KHR_xlib_surface` | `VK_USE_PLATFORM_XLIB_KHR` | X11 Xlib library
`VK_KHR_xcb_surface` | `VK_USE_PLATFORM_XCB_KHR` | X11 Xcb library
`VK_KHR_wayland_surface` | `VK_USE_PLATFORM_WAYLAND_KHR` | Wayland
`VK_KHR_mir_surface` | `VK_USE_PLATFORM_MIR_KHR` | Mir
`VK_KHR_android_surface` | `VK_USE_PLATFORM_ANDROID_KHR` | Android Native
`VK_KHR_win32_surface` | `VK_USE_PLATFORM_WIN32_KHR` | Windows Win32