This is actually not necessary, because RGBLINK would warn about missing labels.
Besides, through semi-esoteric ways, it is possible to define more labels in this scope,
and there's no reason to prevent that.
POSIX leaves undefined the order of output if stderr is injected into stdout,
and in practice it differs on Windows (Linux buffers both streams separately,
Windows interleaves them as they arrive without buffering).
This should help testing on other platforms
