[SOLVED] How can I modify a Makefile to support cross compilation?

How can I modify a Makefile to support cross compilation?

I have the following Makefile:

CC=g++

top_srcdir=$(SRC_DIR)/cpp/src/

INCLUDES:= -I $(top_srcdir) -I $(top_srcdir)command_classes -I $(top_srcdir)platform -I $(top_srcdir)value_classes
LIBS:= -lopenzwave -lpthread -ludev
LDFLAGS += -L$(SRC_DIR) -Wl,-R$(SRC_DIR) '-Wl,-R$$ORIGIN'

all:    ozw

ozw: Main.cpp
    $(CC) $(INCLUDES) -c Main.cpp -o ozw-power-on-off.o
    $(CC) $(LIBS) $(LDFLAGS) ozw-power-on-off.o -o ozw-power-on-off.out

clean:
    rm -rf *.o *.out

I execute it with the following command:

make ARCH=$TARGET_ARCH \
     CROSS_COMPILE=$TARGET_PREFIX \
     SRC_DIR=$ROOT/$PKG_BUILD

But it ignores the ARCH and CROSS_COMPILE values. I tried to replace $(CC) with $(MAKE) and added -$(MAKEFLAGS), but it was saying Nothing to be done for 'Main.cpp'.

How can I fix it and add cross compilation support?

Solution

A possible example of something I would try is below, assuming $ARCH gets mapped to "arm" in this trivial example. I haven't tested it, but I have done something similar before.

CC=g++
CC-arm=arm-g++

ozw: Main.cpp
    $(CC-$(ARCH)) $(INCLUDES) -c Main.cpp -o ozw-power-on-off.o
    $(CC-$(ARCH)) $(LIBS) $(LDFLAGS) ozw-power-on-off.o -o ozw-power-on-off.out

This assumes that the toolchain exists in your path.

It might also modify it such that CC=$(PREFIX)-g++. It all depends on what you pass into it maps against your toolchain's naming convention.