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# OpenGL Segfault with core profile context

## 1 post in this topic

After getting fed up with issues I was having related to OpenGL and Catalyst drivers, I decided to upgrade my GPU and this time I went with Nvida. Now all my problems are behind me right? Not really.

When I try and run this basic program I get a segfault. It seems to happen at the first call to a GL function other than glGetString or equivelent. In this case, it occures at glGenVertexArrays. It only happens if I use a core profile context. If I use a compatability context, everything works. Edit: Checked the pointer for glGenVertexArrays and it is null. Is this a driver bug or maybe a GLEW bug?


#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <stdlib.h>
#include <stdio.h>

#define GLSL(src) "#version 430 core\n" #src

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if(key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
glfwSetWindowShouldClose(window, GL_TRUE);
}

GLuint create_program(const char* vertex_source, const char* fragment_source)
{

}

layout(location = 0) in vec3 vertex_position;

void main()
{
gl_Position = vec4(vertex_position, 1.0);
}
);

out vec4 frag_color;

void main()
{
frag_color = vec4(1.0, 0.0, 0.0, 1.0);
}
);

int main(int argc, char* argv[])
{
if(!glfwInit())
exit(EXIT_FAILURE);

glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
//if we set GLFW_OPENGL_PROFILE to GLFW_OPENGL_CORE_PROFILE
//instead of GLFW_OPENGL_COMPAT_PROFILE the program will
//segfault at line 98, call to glGenVertexArrays
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

GLFWwindow* window = glfwCreateWindow(512, 512, "OpenGL", NULL, NULL);

if(!window)
{
glfwTerminate();
exit(EXIT_FAILURE);
}

glfwSetKeyCallback(window, key_callback);
glfwMakeContextCurrent(window);

GLenum glewError = glewInit();

if(glewError != GLEW_OK)
{
glfwTerminate();
exit(EXIT_FAILURE);
}

printf("OpenGL Version: %s\n\n", glGetString(GL_VERSION));

float position[] =
{
1.0f, 1.0f, 0.0f,
-1.0f, 1.0f, 0.0f,
1.0f, -1.0f, 0.0f,
-1.0f, -1.0f, 0.0f
};

unsigned short indices[] =
{
1, 0, 2,
3, 1, 2
};

GLuint vao = 0;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

GLuint index_buffer = 0;
GLuint vertex_buffer = 0;

glGenBuffers(1, &index_buffer);
glGenBuffers(1, &vertex_buffer);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), &indices, GL_STATIC_DRAW);

glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(position), &position, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(0);

while(!glfwWindowShouldClose(window))
{
glClear(GL_COLOR_BUFFER_BIT);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, NULL);
glfwSwapBuffers(window);
glfwPollEvents();
}

glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}

Edited by Chris_F
0

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For glGenVertexArrays, try setting glewExperimental = GL_TRUE before calling glewInit. And glGetString is not in the core profile, so you can't use it.

Edit. I read some stuff wrong.

Edited by Sponji
2

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