Segfault on vkGetPhysicalDeviceProperties when calling ImGui_ImplVulkan_Init()

[coronavirus6045]

I have been trying to test ImGui through https://github.com/ocornut/imgui/wiki/Getting-Started#example-if-you-are-using-sdl2sdl3--vulkan and when running causes a segfault on imgui_impl_vulkan.cpp (line 1245) when debugging after calling ImGui_ImplVulkan_Init() in the resource initialization function before the event loop starts.

I use the volk library and even defining IMGUI_IMPL_VULKAN_USE_VOLK does not work

OS: Fedora 42
Compiler: GCC 15.1.1
Build system: Meson

Snippet from main renderer code:
Header:

#include "common.hpp"
#include "vk_device.hpp"
#include "vk_pipeline.hpp"
#include "vk_presentation.hpp"
#include "vk_syncobjects.hpp"
#include "vk_command.hpp"
#include "vk_instance.hpp"
#include "vk_buffers.hpp"
#include "vk_image.hpp"
#include "vk_shader.hpp"
#include "vk_descriptor.hpp"
#include "scene/scene_obj.hpp"

// Third-party
#include <imgui.h>
#include <backends/imgui_impl_sdl2.h>
#include <backends/imgui_impl_vulkan.h>

//#define IMGUI_IMPL_VULKAN_NO_PROTOTYPES
#define IMGUI_IMPL_VULKAN_USE_VOLK

Above #include <imgui.h>, these headers above are for the wrapper classes for native Vk objects.

For volk, it's included in common.hpp and I defined VOLK_IMPLEMENTATION on a separate source file.
Source:

ImGui_ImplSDL2_InitForVulkan(_window);
    ImGui_ImplVulkan_InitInfo init_info{};
    init_info.Instance = _instance->get();
    init_info.PhysicalDevice = _device->get_physical_device();
    init_info.Device = _device->get_device();
    init_info.QueueFamily = _device->get_queue_family();
    init_info.Queue = _device->get_graphics_queue();
    init_info.PipelineCache = nullptr;
    init_info.DescriptorPool = _descriptor_pool->get();
    init_info.RenderPass = _main_pass->get();
    init_info.Subpass = 0;
    init_info.MinImageCount = 2;
    init_info.ImageCount = 2;
    init_info.MSAASamples = VK_SAMPLE_COUNT_1_BIT;
    init_info.Allocator = nullptr;
   init_info.CheckVkResultFn = [] (VkResult res) { if (res != VK_SUCCESS) {THROW_RUNTIME_ERROR("ImGui had a problem.")} };

    ImGui_ImplVulkan_Init(&init_info);

Note: the get functions are written by me for classes that wrap Vk and will return the native Vk object handle.

[ocornut]

#define IMGUI_IMPL_VULKAN_USE_VOLK should be defined in all compilation units using the loader.

[coronavirus6045]

So should I define it on the volk implementation source file or all sources listed by the corresponding header? (e.g. vk_command.cpp from its .hpp)

[coronavirus6045]

I tried defining it on all headers above that all use functions defined by volk, but same result. I could send a link to my repo to add more info about the problem

[coronavirus6045]

Update: I was able to fix by defining IMGUI_IMPL_VULKAN_USE_VOLK in the build system. but is there a way to fix it without defining through build system.

[ocornut]

if you search for all uses of IMGUI_IMPL_VULKAN_USE_VOLK you’d naturally find an answer to your question. Preprocessor directives such as define/ifdef are treated sequentially so order matters, aka if some code use #ifdef XXX before XXX was defined that block wouldn’t be compiled.

The define needs to be seen whenever including imgui_impl_vulkan.h and whenever compiling imgui_impl_vulkan.cpp. The simplest is to add it to your imconfig.h file since by convention we include this everywhere where imgui.h is used.