Opengl triangle not drawn - c++

Question

I'm trying to draw a simple triangle on the screen. The window gets properly set up and everything seems okay to the point, where I'm trying to actually draw stuff. I have the following code, but it doesn't work for some reason.
default_shader_program is program linking shaders shown after the function code
void window::run(void(*update)(), void(*draw)()) {
while (glfwWindowShouldClose(wnd) == 0)
{
update();
glClear(GL_COLOR_BUFFER_BIT);
draw();
GLuint vb;
GLfloat data[12]{
1.f, 1.f, 0.f,
1.f, -1.f, 0.f,
-1.f, 0.f, 0.f
};
glGenBuffers(1, &vb);
glBindBuffer(GL_ARRAY_BUFFER, vb);
glBufferData(GL_ARRAY_BUFFER, 12, data, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
GLuint va;
glGenVertexArrays(1, &va);
glBindVertexArray(va);
glUseProgram(default_shader_program);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vb);
glVertexAttribPointer(
0, // attribute 0. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(0);
glfwSwapBuffers(wnd);
glfwPollEvents();
}
glfwDestroyWindow(wnd);
}
Shaders:
vertexshader:
#version 330 core
layout(location=0) in vec3 vertexPosition;
void main() {
gl_Position = vec4(vertexPosition, 1);
}
fragmentshader:
#version 330 core
out vec3 color;
void main() {
color = vec3(1.0, 0.0, 0.0);
}
Yes, I know, that I am buffering data and doing other stuff in while loop. I know, that it shouldn't be done like that, but the actual problem occured somewhere else and I wanted to see if code will work properly directly inside the loop.

Answer 1

Your array contains 9 elements instead of 12, but that doesn't cause the issue.
The 2nd argument of glBufferData is the buffer size in bytes. Hence the size of the buffer is 9*sizeof(GLfloat) rather than 12:
glBufferData(GL_ARRAY_BUFFER, 12, data, GL_STATIC_DRAW);
glBufferData(GL_ARRAY_BUFFER, 9 * sizeof(GLfloat), data, GL_STATIC_DRAW);