[Dev-luatex] offset in texdeffont.w/tex_def_font

I'm confused by this one: ../../../source/texk/web2c/luatexdir/tex/texdeffont.w: In function ‘tex_def_font’: ../../../source/texk/web2c/luatexdir/tex/texdeffont.w:88:5: warning: variable ‘offset’ set but not used [-Wunused-but-set-variable] Studying the routine I see that gcc is right - but what's the use of the offset keyword then? Best Martin