My triangle doesn't render when I use OpenGL Core Profile 3.2 - cocoa

Question

I have a Cocoa (OSX) project that is currently very simple, I'm just trying to grasp the general concepts behind using OpenGL. I was able to get a triangle to display in my view, but when I went to write my vertex shaders and fragment shaders, I realized I was running the legacy OpenGL core profile. So I switched to the OpenGL 3.2 profile by setting the properties in the pixel format of the view in question before generating the context, but now the triangle doesn't render, even without my vertex or fragment shaders.
I have a controller class for the view that's instantiated in the nib. On -awakeFromNib it sets up the pixel format and the context:
NSOpenGLPixelFormatAttribute attr[] =
{
NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersion3_2Core,
0
};
NSOpenGLPixelFormat *glPixForm = [[NSOpenGLPixelFormat alloc] initWithAttributes:attr];
[self.mainView setPixelFormat:glPixForm];
self.glContext = [self.mainView openGLContext];
Then I generate the VAO:
glGenVertexArrays(1, &vertexArrayID);
glBindVertexArray(vertexArrayID);
Then the VBO:
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);
g_vertex_buffer_data, the actual data for that buffer is defined as follows:
static const GLfloat g_vertex_buffer_data[] = {
-1.0f, -1.0f, 0.0f,
1.0f, -1.0f, 0.0f,
0.0f, 1.0f, 0.0f,
};
Here's the code for actually drawing:
[_glContext setView:self.mainView];
[_glContext makeCurrentContext];
glViewport(0, 0, [self.mainView frame].size.width, [self.mainView frame].size.height);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer);
glVertexAttribPointer(
0,
3,
GL_FLOAT,
GL_FALSE,
0,
(void*)0
);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3); // Starting from vertex 0; 3 vertices total -> 1 triangle
glDisableVertexAttribArray(0);
glFlush();
This code draws the triangle fine if I comment out the NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersion3_2Core, in the NSOpenGLPixelFormatAttribute array, but as soon as I enable OpenGL Core Profile 3.2, it just displays black. Can anyone tell me what I'm doing wrong here?
EDIT: This issue still happens whether I turn my vertex and fragment shaders on or not, but here are my shaders in case it is helpful:
Vertex shader:
#version 150
in vec3 position;
void main() {
gl_Position.xyz = position;
}
Fragment shader:
#version 150
out vec3 color;
void main() {
color = vec3(1,0,0);
}
And right before linking the program, I make this call to bind the attribute location:
glBindAttribLocation(programID, 0, "position");
EDIT 2:
I don't know if this helps at all, but I just stepped through my program, running glGetError() and it looks like everything is fine until I actually call glDrawArrays(), then it returns GL_INVALID_OPERATION. I'm trying to figure out why this could be occurring, but still having no luck.

Answer 1

I figured this out, and it's sadly a very stupid mistake on my part.
I think the issue is that you need a vertex shader and a fragment shader when using 3.2 core profile, you can't just render without them. The reason it wasn't working with my shaders was...wait for it...after linking my shader program, I forgot to store the programID in the ivar in my class, so later when I call glUseProgram() I'm just calling it with a zero parameter.
I guess one of the main sources of confusion was the fact that I expected the 3.2 core profile to work without any vertex or fragment shaders.