Hi,

When compiling this GLSL compute shader:

===
#version 430

layout(local_size_x = 1) in;
uniform restrict writeonly image2D outbuf;

vec4 CS_OUTPUT_VAL;

vec4 func() {
        return CS_OUTPUT_VAL;
}

void main()
{       
        CS_OUTPUT_VAL = vec4(0.0, 0.0, 0.0, 1.0);
        vec4 val = func(); 
        imageStore(outbuf, ivec2(0, 0), val);
}
===

I get this warning:

Shader compile log: 0:9(9): warning: `CS_OUTPUT_VAL' used uninitialized

If I move func() below main() (with a forward declaration), the warning goes away.