OpenGl glCreateShader makes window white and gives an error - opengl

Question

When I'm trying to create shader with glCreateShader and running my program, the window i just made goes white and gives me an error:
Exception thrown at 0x03D312F0 (atioglxx.dll) in OpenGl.exe: 0xC0000005: Access violation reading location 0x73553A43.
Does anyone know, why is this happening?
Here's my code
#include <GL/glew.h>
#include <GLFW\glfw3.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
float speed = 0.005;
float edge = 3.0;
float move = 0.0;
float zamik = 0.1;
GLFWwindow *window;
// initialize GLFW
if (!glfwInit())
{
return -1;
}
// create a window mode and its OpenGl context
window = glfwCreateWindow(640, 480, "Window", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
//make the windows contex current
glfwMakeContextCurrent(window);
glewInit();
GLenum err = glewInit();
if (GLEW_OK != err)
{
/* Problem: glewInit failed, something is seriously wrong. */
fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
}
GLfloat verts[] =
{
0.0f, 0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f
};
/*GLfloat color[] =
{
255, 0, 0,
100, 255, 0,
0, 0, 255,
255, 255, 255
};*/
GLuint vertexShader;
vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, "C:\Users\Ghost.corp\Documents\Visual Studio 2015\Projects\OpenGl\OpenGl\VertexShader.shdVertx", NULL);
//glCompileShader(vertexShader);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_PROFILE, 0);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
glfwWindowHint(GLFW_SAMPLES, 4);
//loop
while (!glfwWindowShouldClose(window))
{
//clears our screen
glClear(GL_COLOR_BUFFER_BIT);
//render opengl content
glEnableClientState(GL_VERTEX_ARRAY);
//glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, verts);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 3);
//glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
//sweap front and back buffers
glfwSwapBuffers(window);
glfwPollEvents();
//glColorPointer(4, GL_FLOAT, 0, color);
}
glfwTerminate();
return -1;
}
Concentrate on the glCreateShader if I'm passing parameters wrong. Else i dont know.

Answer 1

The glCreateShader looks fine. But for the next line, you should read the shader file first. glShaderSource expects the shader content, and not a path. An example would be:
char *vs_source =
"attribute vec3 pos;\n"
"void main() {\n"
" gl_Position = vec4(pos,1.0);\n"
"}\n";
glShaderSource(vertexShader, 1, (const GLchar**)&vs_source, NULL);
So, first read the file and put the contents into a string, and then pass it to this function.
Loading a file in C, is a bit confusing, so you need a function like this one:
int load_file(const char *filename, char **result)
{
int size = 0;
FILE *f = fopen(filename, "rb");
if (f == NULL)
{
*result = NULL;
return -1; // -1 means file opening fail
}
fseek(f, 0, SEEK_END);
size = ftell(f);
fseek(f, 0, SEEK_SET);
*result = (char *)malloc(size+1);
if (size != fread(*result, sizeof(char), size, f))
{
free(*result);
return -2; // -2 means file reading fail
}
fclose(f);
(*result)[size] = 0;
return size;
}
And then, you can use it in this way:
char *vs_source;
int size;
size = load_file("C:\\Users\\Ghost.corp\\Documents\\Visual Studio 2015\\Projects\\OpenGl\\OpenGl\\VertexShader.shdVertx", &vs_source);
glShaderSource(vertexShader, 1, (const GLchar**)&vs_source, NULL);
You may check the returned size to see there was no problem loading the file. Also, as you are using C, you need to keep in mind freeing this new memory created is on you. If you don't free it, you'll have memory leak.
Resources:
Loading files function is taken from here.