source: drbl_ui/backup/test_busybox/busybox-1.7.2/scripts/Makefile.host @ 59

# ==========================================================================
# Building binaries on the host system
# Binaries are used during the compilation of the kernel, for example
# to preprocess a data file.
#
# Both C and C++ is supported, but preferred language is C for such utilities.
#
# Samle syntax (see Documentation/kbuild/makefile.txt for reference)
# hostprogs-y := bin2hex
# Will compile bin2hex.c and create an executable named bin2hex
#
# hostprogs-y    := lxdialog
# lxdialog-objs := checklist.o lxdialog.o
# Will compile lxdialog.c and checklist.c, and then link the executable
# lxdialog, based on checklist.o and lxdialog.o
#
# hostprogs-y      := qconf
# qconf-cxxobjs   := qconf.o
# qconf-objs      := menu.o
# Will compile qconf as a C++ program, and menu as a C program.
# They are linked as C++ code to the executable qconf

# hostprogs-y := conf
# conf-objs  := conf.o libkconfig.so
# libkconfig-objs := expr.o type.o
# Will create a shared library named libkconfig.so that consist of
# expr.o and type.o (they are both compiled as C code and the object file
# are made as position independent code).
# conf.c is compiled as a c program, and conf.o is linked together with
# libkconfig.so as the executable conf.
# Note: Shared libraries consisting of C++ files are not supported

__hostprogs := $(sort $(hostprogs-y)$(hostprogs-m))

# hostprogs-y := tools/build may have been specified. Retreive directory
obj-dirs += $(foreach f,$(__hostprogs), $(if $(dir $(f)),$(dir $(f))))
obj-dirs := $(strip $(sort $(filter-out ./,$(obj-dirs))))


# C code
# Executables compiled from a single .c file
host-csingle  := $(foreach m,$(__hostprogs),$(if $($(m)-objs),,$(m)))

# C executables linked based on several .o files
host-cmulti := $(foreach m,$(__hostprogs),\
       $(if $($(m)-cxxobjs),,$(if $($(m)-objs),$(m))))

# Object (.o) files compiled from .c files
host-cobjs  := $(sort $(foreach m,$(__hostprogs),$($(m)-objs)))

# C++ code
# C++ executables compiled from at least on .cc file
# and zero or more .c files
host-cxxmulti := $(foreach m,$(__hostprogs),$(if $($(m)-cxxobjs),$(m)))

# C++ Object (.o) files compiled from .cc files
host-cxxobjs  := $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))

# Shared libaries (only .c supported)
# Shared libraries (.so) - all .so files referenced in "xxx-objs"
host-cshlib := $(sort $(filter %.so, $(host-cobjs)))
# Remove .so files from "xxx-objs"
host-cobjs  := $(filter-out %.so,$(host-cobjs))

#Object (.o) files used by the shared libaries
host-cshobjs  := $(sort $(foreach m,$(host-cshlib),$($(m:.so=-objs))))

__hostprogs     := $(addprefix $(obj)/,$(__hostprogs))
host-csingle  := $(addprefix $(obj)/,$(host-csingle))
host-cmulti := $(addprefix $(obj)/,$(host-cmulti))
host-cobjs  := $(addprefix $(obj)/,$(host-cobjs))
host-cxxmulti := $(addprefix $(obj)/,$(host-cxxmulti))
host-cxxobjs  := $(addprefix $(obj)/,$(host-cxxobjs))
host-cshlib := $(addprefix $(obj)/,$(host-cshlib))
host-cshobjs  := $(addprefix $(obj)/,$(host-cshobjs))
obj-dirs        := $(addprefix $(obj)/,$(obj-dirs))

#####
# Handle options to gcc. Support building with separate output directory

_hostc_flags   = $(HOSTCFLAGS)   $(HOST_EXTRACFLAGS)   $(HOSTCFLAGS_$(*F).o)
_hostcxx_flags = $(HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) $(HOSTCXXFLAGS_$(*F).o)

ifeq ($(KBUILD_SRC),)
__hostc_flags = $(_hostc_flags)
__hostcxx_flags = $(_hostcxx_flags)
else
__hostc_flags = -I$(obj) $(call flags,_hostc_flags)
__hostcxx_flags = -I$(obj) $(call flags,_hostcxx_flags)
endif

hostc_flags    = -Wp,-MD,$(depfile) $(__hostc_flags)
hostcxx_flags  = -Wp,-MD,$(depfile) $(__hostcxx_flags)

#####
# Compile programs on the host

# Create executable from a single .c file
# host-csingle -> Executable
quiet_cmd_host-csingle  = HOSTCC  $@
      cmd_host-csingle  = $(HOSTCC) $(hostc_flags) -o $@ $< \
      $(HOST_LOADLIBES) $(HOSTLOADLIBES_$(@F))
$(host-csingle): %: %.c FORCE
  $(call if_changed_dep,host-csingle)

# Link an executable based on list of .o files, all plain c
# host-cmulti -> executable
quiet_cmd_host-cmulti = HOSTLD  $@
      cmd_host-cmulti = $(HOSTCC) $(HOSTLDFLAGS) -o $@ \
        $(addprefix $(obj)/,$($(@F)-objs)) \
        $(HOST_LOADLIBES) $(HOSTLOADLIBES_$(@F))
$(host-cmulti): %: $(host-cobjs) $(host-cshlib) FORCE
  $(call if_changed,host-cmulti)

# Create .o file from a single .c file
# host-cobjs -> .o
quiet_cmd_host-cobjs  = HOSTCC  $@
      cmd_host-cobjs  = $(HOSTCC) $(hostc_flags) -c -o $@ $<
$(host-cobjs): %.o: %.c FORCE
  $(call if_changed_dep,host-cobjs)

# Link an executable based on list of .o files, a mixture of .c and .cc
# host-cxxmulti -> executable
quiet_cmd_host-cxxmulti = HOSTLD  $@
      cmd_host-cxxmulti = $(HOSTCXX) $(HOSTLDFLAGS) -o $@ \
        $(foreach o,objs cxxobjs,\
        $(addprefix $(obj)/,$($(@F)-$(o)))) \
        $(HOST_LOADLIBES) $(HOSTLOADLIBES_$(@F))
$(host-cxxmulti): %: $(host-cobjs) $(host-cxxobjs) $(host-cshlib) FORCE
  $(call if_changed,host-cxxmulti)

# Create .o file from a single .cc (C++) file
quiet_cmd_host-cxxobjs  = HOSTCXX $@
      cmd_host-cxxobjs  = $(HOSTCXX) $(hostcxx_flags) -c -o $@ $<
$(host-cxxobjs): %.o: %.cc FORCE
  $(call if_changed_dep,host-cxxobjs)

# Compile .c file, create position independent .o file
# host-cshobjs -> .o
quiet_cmd_host-cshobjs  = HOSTCC  -fPIC $@
      cmd_host-cshobjs  = $(HOSTCC) $(hostc_flags) -fPIC -c -o $@ $<
$(host-cshobjs): %.o: %.c FORCE
  $(call if_changed_dep,host-cshobjs)

# Link a shared library, based on position independent .o files
# *.o -> .so shared library (host-cshlib)
quiet_cmd_host-cshlib = HOSTLLD -shared $@
      cmd_host-cshlib = $(HOSTCC) $(HOSTLDFLAGS) -shared -o $@ \
        $(addprefix $(obj)/,$($(@F:.so=-objs))) \
        $(HOST_LOADLIBES) $(HOSTLOADLIBES_$(@F))
$(host-cshlib): %: $(host-cshobjs) FORCE
  $(call if_changed,host-cshlib)

targets += $(host-csingle)  $(host-cmulti) $(host-cobjs)\
     $(host-cxxmulti) $(host-cxxobjs) $(host-cshlib) $(host-cshobjs)