for a while i was trying to get the latest snapshot compiled on an old linux box. (running dapper).
while running make, i got the following error:

MAKE all cmd/
CC cmd/util.o
cc: '-b' must come at the start of the command line
make[1]: *** [util.o] Error 1
make: *** [dall] Error 2

but i couldn’t find the -b option anywhere grepping through the (make)files:

$ grep -w -r -- -b *
rc/sh.wmii:             dmenu -b -fn $WMII_FONT
rc/sh.wmii:     os -b -d ${hostenv HOME} $* &

eventuall it turned to be a very funky thing. namely, an older version of mercurial!
the command to generate the snapshot version was wonky, and thus returned the help output of hg, giving a -b option to the compiler….

after this was fixed, i got the following error:

CC cmd/menu/menu.o
cmd/menu/menu.c:228: error: 'XK_KP_Space' undeclared
cmd/menu/menu.c:228: error: 'XK_KP_Equal' undeclared
cmd/menu/menu.c:229: error: 'XK_KP_Enter' undeclared
cmd/menu/menu.c:230: error: 'XK_Return' undeclared

which lookes like missing a X11 include, and yes the following fixes that:

#include <X11/keysym.h>

happy wmii-3.6′ing!