How to write a Makefile

1
How to write a Makefile

• Based on tutorial at
• http//www.dirac.org/p/TA/tutorials/makefiles/make
  files.html

2
Introduction

• Tool used to make it easier to compile
• Compile only what needs to be compiled
• Every line of a makefile is one of three types
• Assignments
• Target lines
• Rule lines

3
Assignments

• By convention, all variables in a makefile are
  uppercase.
• Spaces are irrelevant around the sign.
• CC gcc
• This is valid
• LIBS "-lncurses -lm -lsdl"
• Quote the asterisk
• MYFACE ")"
• The following line prints the string "gcc"
• CC gcc
• echo CC

4
Target Lines

• Here is an example of a target line with
  dependencies
• all main.o main.h mycode.o mycode.h
• and here is a target line without dependencies
• clean
• Do not begin with a space/tab

5
Rule Lines

• Each target line is followed by 0 or more rule
  lines
• Each rule line must start with a TAB
• Examples
• ltTABgt gcc -g -o myfile myfile.c
• ltTABgt rm -rf core .o
• ltTABgt echo "hello"

6
Dependencies

• OBJS mycode.o
• CC gcc
• CFLAGS -Wall -O3
• all OBJS
• ltTABgt CC CFLAGS OBJS -o mycode
• mycode.o mycode.c
• ltTABgt CC -c CFLAGS mycode.c

7
Some points to note

• make executes the first target
• Note that the rule to make dependents must come
  AFTER you declare them to be a dependence
• So following example is incorrect
• mycode1.o
• ltTABgt gcc -c -Wall mycode1.c
• all mycode1.o mycode2.o
• ltTABgt gcc -Wall mycode1.o mycode2.o -o
  CoolProgram
• mycode2.o
• ltTABgt gcc -c -Wall mycode2.c

8
Example

• CC gcc
• OBJS mycode1.o mycode2.o
• CFLAGS -c -O3 -g -Wall
• LFLAGS -O3 -g -Wall
• all OBJS
• ltTABgt CC LFLAGS OBJS -o MultiFileCode
• mycode1.o mycode1.c
• ltTABgt CC CFLAGS mycode1.c
• mycode2.o mycode2.c
• ltTABgt CC CFLAGS mycode2.o

9
Improved Example

• CC gcc
• OBJS mycode1.o mycode2.o
• CFLAGS -c -O3 -g -Wall
• LFLAGS -O3 -g -Wall
• all OBJS
• ltTABgt CC LFLAGS OBJS -o MultiFileCode
• .c.o
• ltTABgt CC CFLAGS lt

10
Another Example

• EXE animals
• SRC animals.c foo.c bar.c
• CC gcc
• CC_OPTIONS -g -Wall
• CS678 /home/user/prasun/678
• INCLUDES -I(CS678)
• CFLAGS (CC_OPTIONS) (INCLUDES)
• LIBS -L(CS678) lcs678
• OBJ (SRC.c.o)
• (EXE) (OBJ)
• ltTABgt (CC) (CC_OPTIONS) -o _at_ (OBJ) (LIBS)
• clean
• ltTABgt rm -f (EXE) .o a.out core
• depend Makefile (SRC)
• ltTABgt makedepend (INCLUDES) (SRC)
• end of Makefile DO NOT DELETE THIS LINE --
  make depend depends on it.

11
Other pointers

• Symbols in makefile
• http//www.informatik.uni-freiburg.de/mai/files/m
  akeReference.html
• Makefile Tutorial at College of Hawaii
• http//www.eng.hawaii.edu/Tutor/Make/
• Makefile Tutorial at Rutgers
• http//www.hsrl.rutgers.edu/ug/make_help.html