In my c/c++ files, there are multiple #define. As an example:
#ifdef LIBVNCSERVER_HAVE_LIBZ
/* some code */
#ifdef LIBVNCSERVER_HAVE_LIBJPEG
/* some more cod
-DLIBVNCSERVER_HAVE_LIBZ -DLIBVNCSERVER_HAVE_LIBJPEG
You could pass those in CPPFLAGS
,
CPPFLAGS = -DLIBVNCSERVER_HAVE_LIBZ -DLIBVNCSERVER_HAVE_LIBJPEG
or make new variable
CUSTOMDEFINES = -DLIBVNCSERVER_HAVE_LIBZ -DLIBVNCSERVER_HAVE_LIBJPEG
and pass it to CPPFLAGS = -DEXISTINGFLAGS $(CUSTOMDEFINES)
Those are finally will pass to gcc/g++ -D...
$(CC) $(CPPFLAGS)