If rendering with LittleCMS2 is activated (see rendering method) you can define how to handle out-of-gamut colors when converting between color spaces. A selection box in the export, output color profile, and soft proof modules gives you a choice of the following rendering intents:

perceptual
Best suited to photographs as it maintains the relative position of colors. This is usually the best choice.
relative colorimetric
Out-of-gamut colors are converted to colors having the same lightness, but different saturation. Other colors remain unmodified.
saturation
Saturation is retained but lightness is slightly changed.
absolute colorimetric
Keep the white point.