alexmalmis@PC ~/dwm> make
dwm build options:
CFLAGS   = -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os -I/usr/X11R6/include -I/usr/include/freetype2 -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=2 -DVERSION="6.1" -DXINERAMA
LDFLAGS  = -L/usr/X11R6/lib -lX11 -lXinerama -lfontconfig -lXft
CC       = cc
cp config.def.h config.h
cc -c -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os -I/usr/X11R6/include -I/usr/include/freetype2 -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=2 -DVERSION=\"6.1\" -DXINERAMA drw.c
cc -c -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os -I/usr/X11R6/include -I/usr/include/freetype2 -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=2 -DVERSION=\"6.1\" -DXINERAMA dwm.c
dwm.c: In function ‘applysizehints’:
dwm.c:55:57: error: ‘gappx’ undeclared (first use in this function)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:325:14: note: in expansion of macro ‘WIDTH’
    *x = sw - WIDTH(c);
              ^~~~~
dwm.c:55:57: note: each undeclared identifier is reported only once for each function it appears in
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:325:14: note: in expansion of macro ‘WIDTH’
    *x = sw - WIDTH(c);
              ^~~~~
dwm.c: In function ‘configurerequest’:
dwm.c:55:57: error: ‘gappx’ undeclared (first use in this function)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:608:33: note: in expansion of macro ‘WIDTH’
     c->x = m->mx + (m->mw / 2 - WIDTH(c) / 2); /* center in x direction */
                                 ^~~~~
dwm.c: In function ‘manage’:
dwm.c:55:57: error: ‘gappx’ undeclared (first use in this function)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:1042:13: note: in expansion of macro ‘WIDTH’
  if (c->x + WIDTH(c) > c->mon->mx + c->mon->mw)
             ^~~~~
dwm.c: In function ‘movemouse’:
dwm.c:55:57: error: ‘gappx’ undeclared (first use in this function)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:1173:51: note: in expansion of macro ‘WIDTH’
    else if (abs((selmon->wx + selmon->ww) - (nx + WIDTH(c))) < snap)
                                                   ^~~~~
dwm.c: In function ‘resizeclient’:
dwm.c:1299:16: error: ‘gappx’ undeclared (first use in this function)
    gapoffset = gappx;
                ^~~~~
dwm.c: In function ‘showhide’:
dwm.c:55:57: error: ‘gappx’ undeclared (first use in this function)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:1651:28: note: in expansion of macro ‘WIDTH’
   XMoveWindow(dpy, c->win, WIDTH(c) * -2, c->y);
                            ^~~~~
dwm.c: In function ‘tile’:
dwm.c:56:57: error: ‘gappx’ undeclared (first use in this function)
 #define HEIGHT(X)               ((X)->h + 2 * (X)->bw + gappx)
                                                         ^~~~~
dwm.c:1715:10: note: in expansion of macro ‘HEIGHT’
    my += HEIGHT(c);
          ^~~~~~
make: *** [Makefile:18: dwm.o] Error 1