VKAPI_ATTR and VKAPI_CALL macros in Vulkan

Question

I have been searching and I still am not sure what VKAPI_ATTR and VKAPI_CALL are. I am not sure if they are suppose to be a macro

Answer 1

They are defined in vk_platform.h.

They are C preprocessor macros that expand to platform-dependent (and often compiler-specific) function attributes.

The spec defines what they are supposed to do.
But basically each of VKAPI_ATTR, VKAPI_CALL and VKAPI_PTR is distiguished by the spot it has to be in the function declaration to satisfy the C (potentially compiler-dependent) syntax.
Their value(s) are things like the chosen calling convention (e.g. __stdcall) for the platform (detected at compile time).