Next-to-next-to-leading order QCD analysis of combined data for $xF_3$ structure function and higher--twist contribution

The simultaneous QCD analysis of the $xF_3$ structure functions measured in deep-inelastic scattering by several collaborations is done up to 3--loop order of QCD. The x dependence of the higher--twist contribution is evaluated and turns out to be in a qualitative agreement with the results of "old" CCFR data analysis and with renormalon approach predictions. The Gross--Llewellyn Smith sum rule and its higher--twist corrections are evaluated.