I
think I could figure out the reason of this problem. Actually emergency
stretch is broken in all cases it seems. In luatex source code I see:
source/texk/web2c/luatexdir/tex/commands.w:
primitive_tex("emergencystretch",
assign_dimen_cmd, dimen_base
+ emergency_stretch_code, dimen_base);
source/texk/web2c/luatexdir/tex/equivalents.h:#define
emergency_stretch_par
glue_par(emergency_stretch_code)
source/texk/web2c/luatexdir/tex/equivalents.h:#
define glue_par(A) equiv(glue_base+(A))
I
could be wrong but to me it seems we assign some value to emergency
stretch “variable” setting using “emergencystretch” command and we use
another via emergency_stretch_par.
Unfortunately
I am not able to build luatex locally on Windows Platform, only sync
code from SVN repository.