title: Defining Macros on the Command Line And In The Makefile ,Working on linux using gcc, writing c code
body: <p>I have a file named: Makefile and a main.c file 
  i am doing the next code in the main.c file</p>
  
  <pre><code>int main(int argc, char *argv[])
  {
  
      //if 0 then it is default scheduling which is Round Robin.
      //if 1 then the scheduling will be Round Robin.
      //if 2 then the scheduling will be Priority based.
      //if 3 then both scheduling are acceptable, and we decide to use Round Robin.
      int scheduling = 0; 
      #ifdef SCHED_RR
              printf("SCHED_RR is defined\n");
              #ifdef SCHED_PB
                      printf("and also SCHED_PB is defined\n");
                      scheduling = 3;
              #else
                      scheduling = 1;
              #endif
      #elseif SCHED_PB
              printf("SCHED_PB is defined\n")
              scheduling = 2;
      #endif
  
      printf("the number of the scheduling is %d\n",scheduling);
      printf("bye bye\n");
  
      return 0;
  
  }//main
  </code></pre>
  
  <p>as you can see i am checking if a macro has been defined and which one.
  now i want to run the program with my Makefile doing the next command line</p>
  
  <pre><code>make some_var=SCHED_RR
  </code></pre>
  
  <p>this pseudo command (because i don't know how to really do it) is meant to predefine the macro SCHED_RR
  also i want to be able to write the command</p>
  
  <pre><code>make some_var=SCHED_PB
  </code></pre>
  
  <p>and </p>
  
  <pre><code>make some_var1=SCHED_RR some_var2=SCHED_PB
  </code></pre>
  
  <p>the last one is for the case that someone would want to predefine both scheduling</p>
  
  <p>now my problem is: i don't know how and where to write it in my Makefile
  and also how to write it in the command line?</p>
  
  <p>this is my Makefile which of course shows that my real program is bigger
  so where and what should i add to this make file</p>
  
  <pre><code>OBJS = \
      bio.o\
      console.o\
      exec.o\
      file.o\
      fs.o\
      ide.o\
      ioapic.o\
      kalloc.o\
      kbd.o\
      lapic.o\
      log.o\
      main.o\
      mp.o\
      picirq.o\
      pipe.o\
      proc.o\
      spinlock.o\
      string.o\
      swtch.o\
      syscall.o\
      sysfile.o\
      sysproc.o\
      timer.o\
      trapasm.o\
      trap.o\
      uart.o\
      vectors.o\
      vm.o\
  
  
  
  # Cross-compiling (e.g., on Mac OS X)
  #TOOLPREFIX = i386-jos-elf-
  
  # Using native tools (e.g., on X86 Linux)
  #TOOLPREFIX = 
  
  # Try to infer the correct TOOLPREFIX if not set
  ifndef TOOLPREFIX
  TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2&gt;&amp;1 | grep '^elf32-i386$$' &gt;/dev/null 2&gt;&amp;1; \
      then echo 'i386-jos-elf-'; \
      elif objdump -i 2&gt;&amp;1 | grep 'elf32-i386' &gt;/dev/null 2&gt;&amp;1; \
      then echo ''; \
      else echo "***" 1&gt;&amp;2; \
      echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1&gt;&amp;2; \
      echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1&gt;&amp;2; \
      echo "*** If your i386-*-elf toolchain is installed with a command" 1&gt;&amp;2; \
      echo "*** prefix other than 'i386-jos-elf-', set your TOOLPREFIX" 1&gt;&amp;2; \
      echo "*** environment variable to that prefix and run 'make' again." 1&gt;&amp;2; \
      echo "*** To turn off this error, run 'gmake TOOLPREFIX= ...'." 1&gt;&amp;2; \
      echo "***" 1&gt;&amp;2; exit 1; fi)
  endif
  
  # If the makefile can't find QEMU, specify its path here
  #QEMU = 
  
  # Try to infer the correct QEMU
  ifndef QEMU
  QEMU = $(shell if which qemu &gt; /dev/null; \
      then echo qemu; exit; \
      else \
      qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \
      if test -x $$qemu; then echo $$qemu; exit; fi; fi; \
      echo "***" 1&gt;&amp;2; \
      echo "*** Error: Couldn't find a working QEMU executable." 1&gt;&amp;2; \
      echo "*** Is the directory containing the qemu binary in your PATH" 1&gt;&amp;2; \
      echo "*** or have you tried setting the QEMU variable in Makefile?" 1&gt;&amp;2; \
      echo "***" 1&gt;&amp;2; exit 1)
  endif
  
  
  CC = $(TOOLPREFIX)gcc
  AS = $(TOOLPREFIX)gas
  LD = $(TOOLPREFIX)ld
  OBJCOPY = $(TOOLPREFIX)objcopy
  OBJDUMP = $(TOOLPREFIX)objdump
  #CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
  CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
  CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null &gt;/dev/null 2&gt;&amp;1 &amp;&amp; echo -fno-stack-protector)
  ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
  # FreeBSD ld wants ``elf_i386_fbsd''
  LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2&gt;/dev/null)
  
  xv6.img: bootblock kernel fs.img
      dd if=/dev/zero of=xv6.img count=10000
      dd if=bootblock of=xv6.img conv=notrunc
      dd if=kernel of=xv6.img seek=1 conv=notrunc
  
  xv6memfs.img: bootblock kernelmemfs
      dd if=/dev/zero of=xv6memfs.img count=10000
      dd if=bootblock of=xv6memfs.img conv=notrunc
      dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc
  
  bootblock: bootasm.S bootmain.c
      $(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
      $(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
      $(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
      $(OBJDUMP) -S bootblock.o &gt; bootblock.asm
      $(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
      ./sign.pl bootblock
  
  entryother: entryother.S
      $(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S
      $(LD) $(LDFLAGS) -N -e start -Ttext 0x7000 -o bootblockother.o entryother.o
      $(OBJCOPY) -S -O binary -j .text bootblockother.o entryother
      $(OBJDUMP) -S bootblockother.o &gt; entryother.asm
  
  initcode: initcode.S
      $(CC) $(CFLAGS) -nostdinc -I. -c initcode.S
      $(LD) $(LDFLAGS) -N -e start -Ttext 0 -o initcode.out initcode.o
      $(OBJCOPY) -S -O binary initcode.out initcode
      $(OBJDUMP) -S initcode.o &gt; initcode.asm
  
  kernel: $(OBJS) entry.o entryother initcode kernel.ld
      $(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
      $(OBJDUMP) -S kernel &gt; kernel.asm
      $(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' &gt; kernel.sym
  
  # kernelmemfs is a copy of kernel that maintains the
  # disk image in memory instead of writing to a disk.
  # This is not so useful for testing persistent storage or
  # exploring disk buffering implementations, but it is
  # great for testing the kernel on real hardware without
  # needing a scratch disk.
  MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
  kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode fs.img
      $(LD) $(LDFLAGS) -Ttext 0x100000 -e main -o kernelmemfs entry.o  $(MEMFSOBJS) -b binary initcode entryother fs.img
      $(OBJDUMP) -S kernelmemfs &gt; kernelmemfs.asm
      $(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' &gt; kernelmemfs.sym
  
  tags: $(OBJS) entryother.S _init
      etags *.S *.c
  
  vectors.S: vectors.pl
      perl vectors.pl &gt; vectors.S
  
  ULIB = ulib.o usys.o printf.o umalloc.o uthread.o
  
  _%: %.o $(ULIB)
      $(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^
      $(OBJDUMP) -S $@ &gt; $*.asm
      $(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' &gt; $*.sym
  
  _forktest: forktest.o $(ULIB)
      # forktest has less library code linked in - needs to be small
      # in order to be able to max out the proc table.
      $(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o
      $(OBJDUMP) -S _forktest &gt; forktest.asm
  
  mkfs: mkfs.c fs.h
      gcc -DVarName=$(VarName) -m32 -Werror -Wall -o mkfs mkfs.c
  
  UPROGS=\
      _cat\
      _echo\
      _forktest\
      _grep\
      _init\
      _kill\
      _ln\
      _ls\
      _mkdir\
      _rm\
      _sh\
      _stressfs\
      _usertests\
      _wc\
      _zombie\
      _main\
  
  fs.img: mkfs README $(UPROGS)
      ./mkfs fs.img README $(UPROGS)
  
  -include *.d
  
  clean: 
      rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
      *.o *.d *.asm *.sym vectors.S bootblock entryother \
      initcode initcode.out kernel xv6.img fs.img kernelmemfs mkfs \
      .gdbinit \
      $(UPROGS)
  
  # make a printout
  FILES = $(shell grep -v '^\#' runoff.list)
  PRINT = runoff.list runoff.spec README toc.hdr toc.ftr $(FILES)
  
  xv6.pdf: $(PRINT)
      ./runoff
      ls -l xv6.pdf
  
  print: xv6.pdf
  
  # run in emulators
  
  bochs : fs.img xv6.img
      if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi
      bochs -q
  
  # try to generate a unique GDB port
  GDBPORT = $(shell expr `id -u` % 5000 + 25000)
  # QEMU's gdb stub command line changed in 0.11
  QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
      then echo "-gdb tcp::$(GDBPORT)"; \
      else echo "-s -p $(GDBPORT)"; fi)
  ifndef CPUS
  CPUS := 1
  endif
  QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS) -m 512 $(QEMUEXTRA)
  
  qemu: fs.img xv6.img
      $(QEMU) -serial mon:stdio $(QEMUOPTS)
  
  qemu-memfs: xv6memfs.img
      $(QEMU) xv6memfs.img -smp $(CPUS)
  
  qemu-nox: fs.img xv6.img
      $(QEMU) -nographic $(QEMUOPTS)
  
  .gdbinit: .gdbinit.tmpl
      sed "s/localhost:1234/localhost:$(GDBPORT)/" &lt; $^ &gt; $@
  
  qemu-gdb: fs.img xv6.img .gdbinit
      @echo "*** Now run 'gdb'." 1&gt;&amp;2
      $(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB)
  
  qemu-nox-gdb: fs.img xv6.img .gdbinit
      @echo "*** Now run 'gdb'." 1&gt;&amp;2
      $(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
  
  # CUT HERE
  # prepare dist for students
  # after running make dist, probably want to
  # rename it to rev0 or rev1 or so on and then
  # check in that version.
  
  EXTRA=\
      mkfs.c ulib.c user.h cat.c echo.c forktest.c grep.c kill.c\
      ln.c ls.c mkdir.c rm.c stressfs.c usertests.c wc.c zombie.c\
      printf.c umalloc.c main.c\
      README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\
      .gdbinit.tmpl gdbutil\
  
  dist:
      rm -rf dist
      mkdir dist
      for i in $(FILES); \
      do \
          grep -v PAGEBREAK $$i &gt;dist/$$i; \
      done
      sed '/CUT HERE/,$$d' Makefile &gt;dist/Makefile
      echo &gt;dist/runoff.spec
      cp $(EXTRA) dist
  
  dist-test:
      rm -rf dist
      make dist
      rm -rf dist-test
      mkdir dist-test
      cp dist/* dist-test
      cd dist-test; $(MAKE) print
      cd dist-test; $(MAKE) bochs || true
      cd dist-test; $(MAKE) qemu
  
  # update this rule (change rev#) when it is time to
  # make a new revision.
  tar:
      rm -rf /tmp/xv6
      mkdir -p /tmp/xv6
      cp dist/* dist/.gdbinit.tmpl /tmp/xv6
      (cd /tmp; tar cf - xv6) | gzip &gt;xv6-rev5.tar.gz
  
  .PHONY: dist-test dist
  </code></pre>
  
  <p>thank you</p>