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Make

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Make
Make
Makefile
Example makefile

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Reading: None, but check out this tutorial on make and/or the make man page

Make

• One of the basic Unix programming tools is "make"

• Make allows you to manage large programming projects
• Allows you to break things into smaller chunks so compiles can be smaller

• Though make is designed for programming tasks, it can be used for any task that requires something to be done when files change

Makefile

• To make make do its thing, you need to give it some instructions
• The instructions are in a file called a makefile

• The file can have any name, but if it is "Makefile" or "makefile," you don't need to specify a name on the command line
• We'll call it a "makefile," no matter what it's called

• Format

• The Makefile contains 4 types of lines, plus comments

• Comments begin with "#"
• Target lines define target files and their dependencies
• Shell command lines define how to create targets
• Macro lines define macros to save typing in the makefile
• Make directive lines

• Target lines

• Format: target: dependencies
• If anything in the dependency list is newer than the target, the target will be regenerated

• "Newer" is simply based on the modification time of the file

• Shell command lines

• Immediately follow a target line, and define how to generate the target
• Any shell command is valid
• Must be preceeded by a tab character

• Macros

• Allow defining a chunk of text by name
• Format: name = value
• Referenced by $(name)
• Macros may be defined in the makefile or on the command line

• Other makefile features

• By default, make knows that you can make a ".o" file from a ".c" file of the same name with "cc -o file.c", so you don't need to specify this command if that's all there is to it
• Make pre-defines some macros

• CC Defines the command name of the C compiler. The default is "cc".
• CFLAGS Defines flags that should always be added to the compiler (for example "-g" to enable debugging)
• $@ Defines the full name of the current target.
• $? Defines the list of dependency files for the current target that are out of date
• $< Defines the name of the current dependency

Simple Example makefile

# I am a comment, and I want to say that the variable CC will be

# the compiler to use.

CC=g++

# Hey!, I am comment number 2. I want to say that CFLAGS will be the

# options I'll pass to the compiler.

CFLAGS=-c -Wall

all: hello

hello: main.o factorial.o hello.o

$(CC) main.o factorial.o hello.o -o hello

main.o: main.cpp

$(CC) $(CFLAGS) main.cpp

factorial.o: factorial.cpp

$(CC) $(CFLAGS) factorial.cpp

hello.o: hello.cpp

$(CC) $(CFLAGS) hello.cpp

clean:

rm *o hello

Less simple makefile (auto-generated)

Here is an example makefile that shows a straightforward use of make.

 
# Makefile for ephem, v 4.28
 
CLDFLAGS =
CFLAGS = $(CLDFLAGS) -O
LDFLAGS = $(CLDFLAGS)
LIBS = -ltermcap -lm
 
EPHEM= aa_hadec.o altj.o altmenus.o anomaly.o cal_mjd.o circum.o comet.o compiler.o constel.o eq_ecl.o flog.o formats.o io.o listing.o main.o mainmenu.o moon.o moonnf.o nutation.o objx.o obliq.o parallax.o pelement.o plans.o plot.o popup.o precess.o reduce.o refract.o riset.o riset_c.o sel_fld.o sex_dec.o srch.o sun.o time.o utc_gst.o version.o watch.o
 
ephem: $(EPHEM)
 cc $(LDFLAGS) -o $@ $(EPHEM) -ltermcap -lm
 
aa_hadec.o: astro.h
 
altj.o: astro.h circum.h screen.h
 
altmenus.o: astro.h circum.h screen.h
 
anomaly.o: astro.h
 
cal_mjd.o: astro.h
 
circum.o: astro.h circum.h screen.h
 
comet.o: astro.h
 
compiler.o: screen.h
 
constel.o: astro.h circum.h screen.h
 
eq_ecl.o: astro.h
 
flog.o: screen.h
 
formats.o: astro.h screen.h
 
io.o: screen.h
 
listing.o: screen.h
 
main.o: astro.h circum.h screen.h
 
mainmenu.o: astro.h circum.h screen.h
 
moon.o: astro.h
 
moonnf.o: astro.h
 
nutation.o: astro.h
 
objx.o: astro.h circum.h screen.h
 
obliq.o: astro.h
 
parallax.o: astro.h
 
pelement.o: astro.h
 
plans.o: astro.h
 
plot.o: screen.h
 
popup.o: screen.h
 
precess.o: astro.h
 
reduce.o: astro.h
 
refract.o: astro.h
 
riset.o: astro.h
 
riset_c.o: astro.h circum.h screen.h
 
sel_fld.o: screen.h
 
srch.o: screen.h
 
sun.o: astro.h
 
time.o: astro.h circum.h
 
utc_gst.o: astro.h
 
version.o: screen.h
 
watch.o: astro.h circum.h screen.h

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