_____                __  __       _
 | ____|_   _____ _ __|  \/  | __ _| | _____
 |  _| \ \ / / _ \ '__| |\/| |/ _` | |/ / _ \
 | |___ \ V /  __/ |  | |  | | (_| |   <  __/
 |_____| \_/ \___|_|  |_|  |_|\__,_|_|\_\___|
 
 Because, why would anyone reimplement make in 
 Javascript when make makes it's own Makefiles? 
 Let Make do the grunt work! *wink* *wink*

NAME

Makefile

DESCRIPTION

This is an auto-regenerating, portable Makefile. just add new sources to your tree and run make. if new sources are found, it will make itself anew to include the new source, no maintenance required. I use ths as a template in subdirectories with sources, my main Makefile (using bsdmake) descends into subdirs and include them. As this is a dependency of itself, new sources will trigger EvermMake to make itself anew! how meta!

USAGE

Just add new sources and run make

EXAMPLE

The "header" part of the Makefile is not automatically generated and is carried from one version to the next. It has the executable mainx depend on the Makefile and below it depends on the .o files. The Makefile itself depends on the sources in the current directory. If you add a new source file, say sub4.c, make will then execute the action for the Makefile target.

The action is a very sophisticated use of shell looping. It passes the Makefile through sed to cut out the header part, then echo and append the sentinel lines to Makefile. The for loop keys on every .c file in the current directory.

It uses basename to create variables with the .o name. The action uses gcc -MM to parse a source file to generate a target with prerequisites.

The following echos generate dependencies for mainx <- .o file <- .c file, etc.

Next, it creates a collected action, clean, for removing the .o file.

Finally, the action does a recursive make to build the executable with the new Makefile!

#
# Evermake Makefile 
#
LD	= gcc
SHELL	= /bin/sh
mainx : Makefile
	$(LD) -o mainx *.o

clean ::
	-$(RM) mainx

Makefile : *.c
	@sed -e '/^### Do Not edit this line$$/,$$d' Makefile \
		> MMM.$$$$ && mv MMM.$$$$ Makefile
	@echo "### Do Not edit this line" >> Makefile
	@echo "### Everything below is auto-generated" >> Makefile
	@for f in *.c ; do echo ===$$f=== 1>&2 ; ff=`basename $$f .c`.o ; \
	gcc -MM $$f ; echo ""; echo "mainx : $$ff" ; echo "$$ff : $$f" ; \
	echo '	$$(CC) $$(CFLAGS) -c '"$$f" ; echo "" ; echo "clean ::" ; \
	echo '	-$$(RM) '"$$ff" ; echo "" ; done >> Makefile
	@$(MAKE)

### Do Not edit this line
### Everything below is auto-generated
main.o: main.c proj.h

mainx : main.o
main.o : main.c
	$(CC) $(CFLAGS) -c main.c

clean ::
	-$(RM) main.o

sub1.o: sub1.c proj.h

mainx : sub1.o
sub1.o : sub1.c
	$(CC) $(CFLAGS) -c sub1.c

clean ::
	-$(RM) sub1.o

sub2.o: sub2.c proj.h

mainx : sub2.o
sub2.o : sub2.c
	$(CC) $(CFLAGS) -c sub2.c

clean ::
	-$(RM) sub2.o

sub3.o: sub3.c proj.h

mainx : sub3.o
sub3.o : sub3.c
	$(CC) $(CFLAGS) -c sub3.c

clean ::
	-$(RM) sub3.o

Suppose the source sub4.c is added to the existing project. It need not be explicitly added to the Makefile, just type make. It regenerates the Makefile and builds the executable accordingly.

% make
===main.c===
===sub1.c===
===sub2.c===
===sub3.c===
===sub4.c===
make[1]: Entering directory `/u/owen/rk/make/src/ex5
'
cc  -c sub4.c
gcc -o mainx *.o
make[1]: Leaving directory `/u/owen/rk/make/src/ex5'
make: `mainx' is up to date.

AUTHORS

Dr R.K. Owens https://owen.sj.ca.us/~rk