Possible way of dealing with auto in C?

[Ashvith10]

I am trying to follow the Vulkan tutorial in C++. I am substituting GLM with CGLM. There is this particular syntax:

glm::mat4 matrix;
glm::vec4 vec;
auto test = matrix * vec;

How should I go about dealing with this in C?

Added the link to tutorial: https://vulkan-tutorial.com/Development_environment#page_Setting-up-a-makefile-project

[recp]

Hi @Ashvith10,

mat4 matrix;
vec4 vec, test;

glm_mat4_mul(matrix, vec, test);

this would be C version (assuming matrix and vec are initialized)

[Ashvith10]

I am getting a bunch of warnings when I run make. Should I be concerned about this? Is there a way/need to remove such warnings?

make
gcc -std=c2x -O2 -o VulkanTest main.c -lglfw -lvulkan -ldl -lpthread -lX11 -lXxf86vm -lXrandr -lXi
main.c: In function ‘main’:
main.c:17:26: warning: passing argument 2 of ‘glm_mat4_mul’ from incompatible pointer type [-Wincompatible-pointer-types]
   17 |     glm_mat4_mul(matrix, vec, test);
      |                          ^~~
      |                          |
      |                          float *
In file included from /usr/local/include/cglm/cglm.h:18,
                 from main.c:2:
/usr/local/include/cglm/mat4.h:315:28: note: expected ‘float (*)[4]’ but argument is of type ‘float *’
  315 | glm_mat4_mul(mat4 m1, mat4 m2, mat4 dest) {
      |                       ~~~~~^~
main.c:17:31: warning: passing argument 3 of ‘glm_mat4_mul’ from incompatible pointer type [-Wincompatible-pointer-types]
   17 |     glm_mat4_mul(matrix, vec, test);
      |                               ^~~~
      |                               |
      |                               float *
/usr/local/include/cglm/mat4.h:315:37: note: expected ‘float (*)[4]’ but argument is of type ‘float *’
  315 | glm_mat4_mul(mat4 m1, mat4 m2, mat4 dest) {
      |                                ~~~~~^~~~
main.c:17:5: warning: ‘glm_mat4_mul’ accessing 64 bytes in a region of size 16 [-Wstringop-overflow=]
   17 |     glm_mat4_mul(matrix, vec, test);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
main.c:17:5: note: referencing argument 2 of type ‘float[4][4]’
main.c:17:5: warning: ‘glm_mat4_mul’ accessing 64 bytes in a region of size 16 [-Wstringop-overflow=]
main.c:17:5: note: referencing argument 3 of type ‘float[4][4]’
/usr/local/include/cglm/mat4.h:315:1: note: in a call to function ‘glm_mat4_mul’
  315 | glm_mat4_mul(mat4 m1, mat4 m2, mat4 dest) {
      | ^~~~~~~~~~~~

Here's the entire code snippet:

#include <stdio.h>
#include <cglm/cglm.h>
#include <vulkan/vulkan.h>
#include <GLFW/glfw3.h>
#define GLFW_INCLUDE_VULKAN

int main(int argc, char **argv) {
    glfwInit();
    glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
    GLFWwindow* window = glfwCreateWindow(800, 600, "Vulkan window", NULL, NULL);

    uint32_t extensionCount = 0;
    vkEnumerateInstanceExtensionProperties(NULL, &extensionCount, NULL);
    printf("%d extensions supported\n", extensionCount);
    mat4 matrix;
    vec4 vec, test;
    glm_mat4_mul(matrix, vec, test);

    while (!glfwWindowShouldClose(window)) {
        glfwPollEvents();
    }

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}

[recp]

@Ashvith10 sorry my mistake, you should use glm_mat4_mulv() to multiply mat4 with vec4 like glm_mat4_mulv(matrix, vec, test); not glm_mat4_mul() (which multiplies two mat4)

it shoud be:

mat4 matrix;
vec4 vec, test;
glm_mat4_mulv(matrix, vec, test);

/* print vec4 if you want  */
/* glm_vec4_print(test, stderr); */