[require]
GLSL >= 1.10

/* built-in function could be overriden, but should not impact
   another shader.
*/

[vertex shader file]
glsl-mvp.vert

[fragment shader]
float myfunc(float);

float abs(float f)
{
    return f-1.0; 
}

void main()
{
    gl_FragColor = vec4(abs(1.0), myfunc(1.0), 0.0, 1.0);
}

[fragment shader]
float myfunc(float f)
{
    return abs(f);
}

[test]
draw rect -1 -1 2 2
probe all rgba 0.0 1.0 0.0 1.0