Segmentation fault on vkCreateInstance

Vulkan
1

i’m new to vulkan and trying to migrate from using function prototypes to VK_NO_PROTOTYPES and getting function pointers myself, need to note that before i started to refactor this everything was fine. i’m loading function pointers like this

//global variables
PFN_vkGetInstanceProcAddr vkGetInstanceProcAddr;
PFN_vkCreateInstance vkCreateInstance;

// function that is called before creating instance
vkGetInstanceProcAddr = (PFN_vkGetInstanceProcAddr)SDL_Vulkan_GetVkGetInstanceProcAddr();
vkCreateInstance = (PFN_vkCreateInstance)vkGetInstanceProcAddr(nullptr, "vkCreateInstance");

i’m creating sdl window before calling function pointers loading, so getting vkGetInstanceProcAddr pointer should end up fine.
i add them in header

extern PFN_vkGetInstanceProcAddr vkGetInstanceProcAddr;
extern PFN_vkCreateInstance vkCreateInstance;

and then i’m trying to create an instance

VkInstance instance;

VkApplicationInfo appInfo = {};
appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
appInfo.pApplicationName = "vulkan";
appInfo.applicationVersion =  VK_MAKE_VERSION(1, 0, 0);
appInfo.pEngineName = "Engine";
appInfo.engineVersion = VK_MAKE_VERSION(1, 0, 0);
appInfo.apiVersion = VK_API_VERSION_1_2;
appInfo.pNext = nullptr;

unsigned int extCount;
SDL_Vulkan_GetInstanceExtensions(window, &extCount, nullptr);
std::vector<const char*> extensions(extCount);
SDL_Vulkan_GetInstanceExtensions(window, &extCount, extensions.data());

VkInstanceCreateInfo instanceInfo = {};
instanceInfo.enabledLayerCount = 0;
instanceInfo.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
instanceInfo.pNext = nullptr;
instanceInfo.pApplicationInfo = &appInfo;
instanceInfo.enabledExtensionCount = extCount;
instanceInfo.ppEnabledExtensionNames = extensions.data();

if (vkCreateInstance(&instanceInfo, nullptr, &instance) != VK_SUCCESS)
		throw std::runtime_error("failed to create vulkan instance");

but when i run that code i receive segmentation fault, so i tried to debug it a little. i found that the error occurs at the vkCreateInstance call, but vkCreateInstance pointer is not NULL, std::cout << (vkCreateInstance == NULL) << std::endl outputs 0, also print vkCreateInstance in gdb outputs $1 = (PFN_vkCreateInstance) 0x555561bde8 <vkCreateInstance> so vkCreateInstance is difenetely not NULL. but what else can cause this to happen if it was working before moving to VK_NO_PROTOTYPES? when i revert loading function pointers back to prototypes, everything starts to work again.

2

For what purpose though?

Heh, why do people keep doing this? All of those members happily accept zero initialization…

SDL_Vulkan_GetInstanceExtensions reserves the right to fail, but return code is not checked.

Pre-null it to make clear whether it was overwritten.

3

I created an example with SDL2.

#include <SDL2/SDL.h>
#include <SDL2/SDL_vulkan.h>
#include <SDL_log.h>
#include <vector>
#include <vulkan/vulkan.h>
#include <vulkan/vulkan_core.h>

PFN_vkGetInstanceProcAddr vkGetInstanceProcAddr;
PFN_vkCreateInstance vkCreateInstance;

int main(int argc, char *argv[]) {
  if (SDL_Init(SDL_INIT_VIDEO) != 0) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_Init: %s\n",
                 SDL_GetError());
    return -1;
  }

  int state = SDL_Vulkan_LoadLibrary("C:\\Windows\\System32\\vulkan-1.dll");
  if (state == -1) {
    SDL_Log("SDL_Vulkan_LoadLibrary failed: %s", SDL_GetError());
    SDL_Quit();
    return -1;
  } else {
    SDL_Log("SDL_Vulkan_LoadLibrary success");
    vkGetInstanceProcAddr =
        (PFN_vkGetInstanceProcAddr)SDL_Vulkan_GetVkGetInstanceProcAddr();
    vkCreateInstance = (PFN_vkCreateInstance)vkGetInstanceProcAddr(
        nullptr, "vkCreateInstance");
    VkInstance instance;

    VkApplicationInfo appInfo = {};
    appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
    appInfo.pApplicationName = "vulkan";
    appInfo.applicationVersion = VK_MAKE_VERSION(1, 0, 0);
    appInfo.pEngineName = "Engine";
    appInfo.engineVersion = VK_MAKE_VERSION(1, 0, 0);
    appInfo.apiVersion = VK_API_VERSION_1_2;
    appInfo.pNext = nullptr;

    unsigned int extCount{2};
    std::vector<const char *> extensions{"VK_KHR_surface", "VK_KHR_win32_surface"};

    VkInstanceCreateInfo instanceInfo = {};
    instanceInfo.enabledLayerCount = 0;
    instanceInfo.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
    instanceInfo.pNext = nullptr;
    instanceInfo.pApplicationInfo = &appInfo;
    instanceInfo.enabledExtensionCount = extCount;
    instanceInfo.ppEnabledExtensionNames = extensions.data();

    if (vkCreateInstance(&instanceInfo, nullptr, &instance) != VK_SUCCESS)
      throw std::runtime_error("failed to create vulkan instance");

    SDL_Log("Vulkan instance created.");
  }

  SDL_Vulkan_UnloadLibrary();
  SDL_Quit();

  return 0;
}

I had never used SDL2 before. So I can make some mistakes. But the Vulkan instance is successfully created. I also defined VK_NO_PROTOTYPES (in CMakeLists.txt).
About your code: I also use a shared library, and your code looks proper.