for the reason i don’t understand sampling a cube map does not work inside a function (when the texture is not set)

here it works:

uniform samplerCube skybox;

void main() {
  color = texture(skybox, vec3(1));
}

result is black as expected

here it does not work:

uniform samplerCube skybox;

vec4 get_skybox_color() {
  return texture(skybox, vec3(1));
}

void main() {
  color = get_skybox_color();
}

in that case it just does not render anything at all and there are no errors produced

it does not work even if i do it like that:

uniform samplerCube skybox;

vec4 get_skybox_color() {
  return vec4(1);
  return texture(skybox, vec3(1)); // this line is never executed obviously
}

void main() {
  color = get_skybox_color();
}

opengl 4.1

could you please help me to understand what’s happening here
thx