  We analyse all available observations of GX 339--4 by XMM-Newton in the hard
spectral state. We jointly fit the spectral data by Comptonization and the
currently best reflection code, relxill. We consider in detail a contribution
from a standard blackbody accretion disc, testing whether its inner radius can
be set equal to that of the reflector. However, this leads to an unphysical
behaviour of the disc truncation radius, implying the soft X-ray component is
not a standard blackbody disc. This appears to be due to irradiation by the
hard X-rays, which strongly dominate the total emission. We consider a large
array of models, testing, e.g., the effects of the chosen energy range, of
adding unblurred reflection, and assuming a lamppost geometry. We find the
effects of relativistic broadening to be relatively weak in all cases. In the
coronal models, we find the inner radius to be large. In the lamppost model,
the inner radius is unconstrained, but when fixed to the innermost stable
orbit, the height of the source is large, which also implies a weak
relativistic broadening. In the former models, the inner radius correlates with
the X-ray hardness ratio, which is consistent with the presence of a truncated
disc turning into a complete disc in the soft state. We also find the degree of
the disc ionization to anti-correlate with the hardness, leading to strong
spectral broadening due to scattering of reflected photons in the reflector in
the softest studied states.
