Creating a Makefile
-------------------

A Makefile is used for automatically compiling and linking your programs 
together.  The first homework assignment used a Makefile for the C++
code.  Here is a sample Makefile:


# makefile for gl prog10.c

CC= cc

# flags 

CFLAGS= -O
LDFLAGS= -s

MODULES=

LIBS= -lgl_s -lc_s

default: prog10

# main compile module

prog10: ${MODULES} prog10.o
        ${CC} ${LDFLAGS} ${MODULES} prog10.o -o prog10 ${LIBS}

# source compilations

prog10.o: prog10.c
        ${CC} -c ${CFLAGS} prog10.c

# remove .o files

clean:
        rm *.o


Rules about Makefiles are as follows:

	1.  Type everything as it is into a file called "Makefile" except
	    the lines after the following lines:

		prog10: ${...

		prog10.o: prog...

		clean:

	    The line that follows each of these line must start with a
	    <tab>.  For example,

	    <tab>${CC} ${LDFLAGS} ${MODULES} prog10.c -o prog10 ${LIBS}

	2.  The lines starting with a "#" sign are comment lines.

	3.  Blank lines are ignored.

	4.  The line containing variable assignment CC= cc is the way to
	    assign a compiler.  These variables are not shell variables, but
	    a special type of variables used only in Makefiles.  You do not
	    necessarily need to use these variables, but I suggest using this
	    Makefile as a template and modifying it for the projects you work
	    on in the near future.

	    Different options here for compilers are:

		cc	Standard C compiler
		CC 	Standard C++ compiler
		gcc	GNU C compiler
		g++	GNU C++ compiler

	    Note: If you want to use gcc as your compiler for your gl C code,
		  you will need to include the -lX11_s library option to
		  the variable called LIBS (further down).

	5.  The line containing CFLAGS is for compiling flags which you so far
	    haven't used when compiling.  The one used in this Makefile is the
	    -O option, which tells the compile to optimize at the default level.
	    Optimization makes things go slightly faster.  You may even use
	    different levels such as -O2 or -O3.  Depending on the machine you
	    are on.

	6.  The line containing LDFLAGS is for linking flags which you also have
	    not used so far.  In this case just accept the flag they use called
	    -s which basically is involved with the linking of the .o files.

	7.  The line containing MODULES is for adding additional C modules such
	    as in the last assignment (Part 3).  There were 3 different modules
	    besides the main module.  In this example, there are no additional
	    modules.

	8.  The line containing LIBS is for including the libraries that you 
	    wish to use.  You already have been using the shared C library,
	    -lc_s, and the shared gl library, -lgl_s.  These are listed here.

	9.  The line containing default: is the line where you put your default
	    compile program.  In other words, when you type "make" it looks for
	    this default line and uses "prog10" in this case.  If this line is
	    not there, you would have to type "make prog10".  This line is useful
	    in case you have more than one program you wish to compile.

	10. The next section is where you put your default main compile module.
	    Always use the name that you are going to call when you use "make
	    name" or in the default: line when you use "make" first.  The format
	    is:

		name: ${MODULES} name.o
		<tab>${CC} ${LDFLAGS} ${MODULES} name.o -o name ${LIBS}

	11. The next section is where you put the source compilation part.  The
	    format is:

		name.o: name.c
		<tab>${CC} -c ${CFLAGS} name.c

	               :
		       :
		    <more modules can go here, see the Makefile used in
		     Part 3 of Homework #4 for examples. >

	12. The last section is for removing old .o files.  All you need to
	    do is leave this part like it is.  Be sure to use the <tab> before
	    the "rm *.o" command.  You need not use the name "clean:" as well.
	    You could put "erase:" instead or whatever you like.


A more complicated Makefile looks like this (this is the one used for the 
homework project #1 and Part 3 of Homework #4):


#
# makefile
#
CC= g++
#
# flags for cs machines
#
CFLAGS= -O 
LDFLAGS = -s
#
AM= am_gl.o am_read.o


LIBS= -lmalloc /usr/lib/libimage.a -lfm_s -lgl_s\
        -lX11_s -lm -lc_s
#

default: am

#### Art Maker Main Compile ####

am: ${AM} am.o
        ${CC} ${LDFLAGS} ${AM} am.o -o am ${LIBS}

#### Vision Studio Object Compile ####

am.o: am.cc
        ${CC} -c ${CFLAGS} am.cc

am_gl.o: am_gl.cc
        ${CC} -c ${CFLAGS} am_gl.cc

am_read.o: am_read.cc
        ${CC} -c ${CFLAGS} am_read.cc


#### CLEAN .o FILES ####

clean:
        rm *.o


Try typing in the first one.  You will be using it in the next project.