OpenGL 2.1 VBO not rendering, blank screen.

OpenGL OpenGL: Basic Coding
1

I’m trying to draw a simple triangle with VBOs, however I can’t get it to work, it’s a blank screen.
What is the issue?

#include<SDL2/SDL.h>
#include<GL/glew.h>
#include<GL/gl.h>

const char* vertshaderSource = R"(
    #version 120
    attribute vec3 pos;

    void main() {
        gl_Position = vec4(pos.xyz, 1);
    }
)";
const char* fragshaderSource = R"(
    #version 120

    void main() {
        gl_FragColor = vec4(1, 0, 0, 1);
    }
)";

struct vert {
    float x, y, z;
};

int main(int argc, char** argv) {
    SDL_Window* window = SDL_CreateWindow("A", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_OPENGL);

    SDL_GLContext glctx = SDL_GL_CreateContext(window);

    glewExperimental = false;
    glewInit();

    SDL_ShowWindow(window);

    glViewport(0, 0, 640, 480);

    GLint vertshader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertshader, 1, &vertshaderSource, 0);
    glCompileShader(vertshader);

    GLint fragshader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragshader, 1, &fragshaderSource, 0);
    glCompileShader(fragshader);

    GLint prog = glCreateProgram();
    glAttachShader(prog, vertshader);
    glAttachShader(prog, fragshader);
    glLinkProgram(prog);

    glEnable(GL_VERTEX_ARRAY);
    vert tri[3] = {{0, 0, 0}, {1, 0, 0}, {0.5f, 1, 0}};
    GLuint trivbo;
    glGenBuffers(1, &trivbo);
    glBindBuffer(GL_ARRAY_BUFFER, trivbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(tri), tri, GL_DYNAMIC_DRAW);

    glClearColor(0, 1, 0.5f, 1);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glUseProgram(prog);
    glBindBuffer(GL_ARRAY_BUFFER, trivbo);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, (void*) 0);
    glDrawArrays(GL_TRIANGLES, 0, 3);

    SDL_GL_SwapWindow(window);

    SDL_Delay(5000);

    SDL_GL_DeleteContext(glctx);
    SDL_DestroyWindow(window);

    return 0;
}
2

This shouldn’t be here.

The second parameter should be 3.

3

Oh wow, I mistook it for the size of a float, sorry.
Thank you so much for this!