Question

I am trying to make my Makefiles platform conditional with statements like:

ifeq ($(UNAME), Linux)
# LINUX version
program_NAME := lib$(TARGET).so
OBJDIR = ../build/linux
endif

ifeq ($(UNAME), MINGW32_NT-6.1)
# WINDOWS version
program_NAME := lib$(TARGET).dll
OBJDIR = ../build/windows
endif

and:

ifeq ($(UNAME), Linux)
# LINUX version
program_INCLUDE_DIRS := \
    /home/ben/projects/g2/src \
    /home/ben/projects/pulse_IO/src \
    /home/ben/projects/core/src

endif

ifeq ($(UNAME), MINGW32_NT-6.1)

# WINDOWS Virtual Machine version
program_INCLUDE_DIRS := \
    E:/g2/src \
    E:/pulse_IO/src \
    E:/core/src

endif

I then compile the src either under Linux or Windows 7 running as a VM (via virtualbox) on a Linux host OS. Problem I haven’t managed to solve is how to get the object files and resulting shared libraries or executables to be written to a platform specific directory, e.g. /build/linux or /build/windows where the source code is in /src

As you can see I’ve added an OBJDIR variable but I can’t figure out how to use that to redirect the .o, .so, .dll, .exe files to the correct dir conditional on platform. I’m sure it should be easy but my research keeps bogging down with articles on vpath usage which I don’t think is what I’m after.

The part of my Makefile I think I need to modify is as follows:

LINK.c := $(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH)

$(program_NAME): $(program_OBJS)
    $(LINK.c) -shared -Wl,-soname,$(program_NAME) $(program_OBJS) -o $(program_NAME)

I should probably be using something smarter like autotools or cmake but it would be great just to get this working for now.

should also add, my list of object files is created as follows:

program_C_OBJS := ${program_C_SRCS:.c=.o}

Have tried:

program_OBJS := $(addprefix $(OBJDIR)/$program_C_OBJS)

but make compains that addprefix has the wrong no. of arguments

Answer 1

For gmake, see Here:

 OBJDIR := objdir
 OBJS := $(addprefix $(OBJDIR)/,foo.o bar.o baz.o)

 $(OBJDIR)/%.o : %.c
         $(COMPILE.c) $(OUTPUT_OPTION) $<

 all: $(OBJS)

 $(OBJS): | $(OBJDIR)

 $(OBJDIR):
         mkdir $(OBJDIR)