The vertex shader:

in vec3 a_Position;
in vec4 a_Color;
in float a_Width;
in vec4 a_JointProduct;
in int a_EntityID;

layout(location=0) out vec3 pos;
layout(location=1) out vec4 color;
layout(location=2) out float v_stroke_width;
layout(location=3) out flat int v_EntityID;
layout(location=4) out vec4 v_joint_product;

layout(std140, binding = 0) uniform Camera
{
  mat4 u_ViewProjection;
};


void main(){
    gl_Position = u_ViewProjection * vec4(a_Position, 1.0);
    pos = vec3(1.0, 1.0, 1.0);
    color = vec4(1.0);
    v_stroke_width = a_Width;
    //v_joint_product = a_JointProduct;
    //v_EntityID = a_EntityID;
}

The fragment shader:

layout(location = 0) out vec4 frag_color;

layout(location=0) in vec3 pos;
layout(location=1) in vec4 v_color;
layout(location=2) in float v_stroke_width;
layout(location=3) in flat int v_EntityID;
layout(location=4) in vec4 v_joint_product;


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

With the above code (and some test data), the follwing is rendered:

Now, if I change the fragment shader //v_joint_product = a_JointProduct; -> v_joint_product = a_JointProduct; (Remove the comment on either of the two commented lines), I get a completely empty result, no triangles, nothing.

I’m running this with the follwing specs, since it may be a driver issue:

Vendor: ATI Technologies Inc.
Renderer: AMD Radeon(TM) Graphics
Version: 4.5.14802 Core Profile/Debug Context 21.40.18.15 30.0.14018.15002

I am incredibly confused as to why this is happening, the shader compiles and links and I get 0 errors, it simply stops working, sorry if it’s an obvious question but I really can’t figure it out, any help is much appreciated.