"comparison always false" is a problem or not?

[Joel Rees]

My experience is that this kind of thing tends to lead to dead code or 
endless loops. Do I need to dig in and find the macro declaration and 
see if I can fix it?

    warning: comparison is always false due to limited range of data 
type

regcomp.c:724
pp_sys.c:302
byterun.c:898
re_comp.c:724
Joel Rees