17 Bit Software 3: The Continuation/17-Bit_The_Continuation_Disc.iso/amigan/amigan 4/make/make.doc

Text File | 1994-01-27 | 5.5 KB | 103 lines

MAKE:  Brought to you by John Toebes and Jack Rouse of

|_o_o|\\   The           Dave Baker    Ed Burnette
|. o.| ||   Software     Stan Chow     Jay Denebeim
| .  | ||    Distillery  Gordon Keener Jack Rouse
| o  | ||                John Toebes   Doug Walker
|  . |//
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     MAKING IT WITH MAKE        MAKE is a UN*X utility which allows you to keep
                                track of your source files no matter how large
  For the Lazy and Ingenious    or complicated your project gets. Suppose you
                                have two source files for a C program: main.c
and subs.c. Let's also say they both #include foofile.h. If you change main.c,
you must recompile main.c and relink.  If you change foofile.h, you must re-
compile both main.c and subs.c.  This isn't too bad with only two files, but
just try to keep track of, say, eight source files...ten...a hundred. MAKE is
designed to help you whether you have one, ten, or one hundred source files.<

The principle behind MAKE is that you specify all the commands required to pro-
duce your program in a file (called 'makefile').  When you want to produce an
                                       up-to-date version of your program, you
program: main.o subs.o                 simply type 'make'; MAKE looks at the
 blink from main.o,subs.o to program   system dates on your source files, de-
 echo "all done!"                      termines which must be recompiled, then
                                       recompiles them and relinks your execut-
main.o: main.c foofile.h               able! A makefile for our simple program
 lc main.c                             with two source files is shown at left.

subs.o: subs.c foofile.h               This simple script tells MAKE that the
 lc subs.o                             file PROGRAM depends (:) on the files
                                       main.o and subs.o, and that to make the
file PROGRAM you execute the 'blink' command on the second line.  You can have
as many filenames separated by blanks as you wish after the colon.  Commands,
if present, must start with a blank or tab.  You may have as many commands as
you wish.

Note that there are entries for main.o, subs.o, and foofile.h. MAKE will see
that PROGRAM depends on main.o, and main.o depends on main.c; it will check the
dates on main.o and main.c to see if the 'lc main.c' (compile) command should
be performed before it links PROGRAM.

Instead of entering an lc command for each .c file you have, you can instead
enter a special dependency that looks like the one at left, below. This tells
           MAKE that whenever it sees an .o file, it must see a dependency upon
.c.o:      a .c file with the same prefixed name. You are relieved of any need
 lc $*.c   to put this dependency in every makefile; instead, MAKE allows you
           to put it in a file called "builtins.make" in your C: directory. If
the expression "$*" is seen in a builtin dependency, MAKE replaces it with the
file name being processed (minus the .c or .o extension, of course).

Now that your makefile is entered, how do you use it to make PROGRAM?  Quite
simple.  Just type 'make'.  MAKE looks in the makefile and sees that PROGRAM is
the first file listed; it therefore assumes that you mean to make PROGRAM. It
then does whatever is necessary to bring PROGRAM up to date.  But what if you
just want to compile 'main.c'?  Also simple. Type 'make main.o'. MAKE takes the
argument and figures out how to make it from the makefile.

In fact, if you have typed in the .c.o dependency above, you can MAKE FARKLE.O
when FARKLE is not even mentioned in the makefile.  As you can see, MAKE is
worth its weight in saved keystrokes alone!

There are several useful command line options on MAKE: "make -n ..." prints the
commands needed to bring "file" up to date to the screen but will not execute
them.  This is great if you just want to see how out-of-date your stuff is. A
"make -k ..." tells MAKE that it should proceed as far as it can without stop-
ping.  If a command fails, MAKE quits without this flag; with the flag, MAKE
continues until it needs the output file from the failed command.

This means that if you compile 50 files and number 27 fails, numbers 28 to 50
are compiled before MAKE needs the .o file for number 27. Last, "make -f <file-
name>" tells MAKE to get its instructions from <filename>, not from "makefile."

MAKE observes ^C interrupts; hit ^C and everything stops.  It also observes ^D
interrupts;  hit ^D and MAKE quits after the current command is executed.<

 FOR THE ADVANCED USER:  There is a limited ability to define macros in a make-
file. Macros are of the form NAME = STRING. Whenever the string $(NAME) is seen
                 in a makefile, STRING is put in its place. For example, you
LC = lc $*       can use the macros at left. This allows you to change your de-
LCD = lc -d $*   fault compiler options rapidly by simply changing the last line
.c.o:            to read $(LCD) [with a -d option] in place of $(LC).
 $(LC)
                 Normally, MAKE types each line to the screen before executing
it. If you prefer silent execution, preface a command with an '@'. Example:<

program: program.o
 @echo "Linking program. . ."
 @blink from lib:c.o,program.o to program verbose lib lib:lc.lib

Enjoy MAKE as much as I do!  Many thanks to John Toebes and Jack Rouse for MAKE-
ing it available!