Chapter 1 (Introduction)

Advanced_Linux_Programming                                                 Chapter_2 

Contents:

ch1-reciprocal     ch1-make     debug.txt

ch1-reciprocal     ALP, p. 18-20

Folder reciprocal contains readme.txt, folder_include, folder_src.

readme.txt     ALP, p. 19-20

Open the terminal in folder reciprocal (Ctrl+Alt+T or F4).

Compile without linking:

gcc -c -I ./include ./src/main.c

gcc -c -D NDEBUG=3 -O2 -I ./include ./src/main.c

g++ -c -I ./include ./src/reciprocal.cpp

g++ -c -D NDEBUG=3 -O2 -I ./include ./src/reciprocal.cpp

Link object files and output the executable `reciprocal':

g++ main.o reciprocal.o -o reciprocal

g++ *.o -o reciprocal

Run the program:

./reciprocal

Usage: ./reciprocal n

n - integer

./reciprocal 1

The reciprocal of 1 is 1

./reciprocal 10

The reciprocal of 10 is 0.1

./reciprocal 7

The reciprocal of 7 is 0.142857

./reciprocal 0

The reciprocal of 0 is inf

NDEBUG disables run-time errors, to focus on programming errors. See:

https://cplusplus.com/reference/cassert/assert/

Clean:

rm *.o

*****************************************************************************************

*****************************************************************************************

*****************************************************************************************

Folder include contains the header file reciprocal.hpp.

reciprocal.hpp     ALP, p. 19

#ifdef __cplusplus

extern "C"

{

#endif

  extern double reciprocal (int i);

#ifdef __cplusplus

}

#endif

*****************************************************************************************

*****************************************************************************************

*****************************************************************************************

Folder src includes the source files reciprocal.cpp and main.c.

reciprocal.cpp     ALP, p. 19

#include <cassert> // for assert()

#include "reciprocal.hpp" // for reciprocal()

double reciprocal (int i)

{

  // i should be non-zero

  assert (i != 0);

  return 1.0 / i;

}

/*

g++ -c -I ./include ./src/reciprocal.cpp

g++ -c -D NDEBUG=3 -O2 -I ./include ./src/reciprocal.cpp

*/

*****************************************************************************************

*****************************************************************************************

*****************************************************************************************

main.c     ALP, p. 18-19

#include <stdio.h> // for printf(), fprintf(), stderr

#include <stdlib.h> // for atoi()

#include "reciprocal.hpp" // for reciprocal()

int main (int argc, char **argv)

{

  if (argc != 2)

  {

    fprintf(stderr, "Usage: ./reciprocal n\n");

    fprintf(stderr, "n - integer\n");

    return 1; // end program, signalling error

  }

  int i;

  i = atoi (argv[1]);

  printf ("The reciprocal of %d is %g\n", i, reciprocal (i));

  return 0; // end program normally

}

/*

gcc -c -I ./include ./src/main.c // compile without linking

gcc -c -D NDEBUG=3 -O2 -I ./include ./src/main.c

g++ -c -I ./include ./src/reciprocal.cpp

g++ -c -D NDEBUG=3 -O2 -I ./include ./src/reciprocal.cpp

Link object files and output the executable `reciprocal':

g++ main.o reciprocal.o -o reciprocal

g++ *.o -o reciprocal

./reciprocal

Usage: ./reciprocal n

n - integer

./reciprocal 1

The reciprocal of 1 is 1

./reciprocal 10

The reciprocal of 10 is 0.1

./reciprocal 7

The reciprocal of 7 is 0.142857

./reciprocal 0

The reciprocal of 0 is inf

rm *.o // clean

*/

*********************************************************************************

*********************************************************************************

*********************************************************************************

*********************************************************************************

*********************************************************************************

ch1-make     ALP, p. 21-22

Note:  We added the file Makefile to folder reciprocal.

Makefile     ALP, p. 21

reciprocal: main.o reciprocal.o

g++ $(CFLAGS) main.o reciprocal.o -o reciprocal

main.o: ./src/main.c ./include/reciprocal.hpp

gcc $(CFLAGS) -I ./include -c ./src/main.c

reciprocal.o: ./src/reciprocal.cpp ./include/reciprocal.hpp

g++ $(CFLAGS) -I ./include -c ./src/reciprocal.cpp

run: reciprocal

./reciprocal $(ARGS)

clean:

rm *.o

Note: The clean target could also remove the executable:

clean:

rm *.o reciprocal

Note:  We added the new tests to readme.txt.

readme.txt     ALP, p. 22

Open the terminal in folder reciprocal (Ctrl+Alt+T or F4).

Compile without linking:

make main.o

gcc -c -I ./include ./src/main.c

make main.o CFLAGS="-D NDEBUG=3 -O2"

gcc -c -D NDEBUG=3 -O2 -I ./include ./src/main.c

make reciprocal.o

g++ -c -I ./include ./src/reciprocal.cpp

make reciprocal.o CFLAGS="-D NDEBUG=3 -O2"

g++ -c -D NDEBUG=3 -O2 -I ./include ./src/reciprocal.cpp

Link object files and output the executable `reciprocal':

make reciprocal

make

g++ main.o reciprocal.o -o reciprocal

g++ *.o -o reciprocal

Run the program:

make run

./reciprocal

Usage: ./reciprocal n

n - integer

make: *** [Makefile:8: run] Error 1

make run ARGS=1

./reciprocal 1

The reciprocal of 1 is 1

make run ARGS=10

./reciprocal 10

The reciprocal of 10 is 0.1

make run ARGS=7

./reciprocal 7

The reciprocal of 7 is 0.142857

make run ARGS=0

./reciprocal 0

The reciprocal of 0 is inf

NDEBUG disables run-time errors, to focus on programming errors. See:

https://cplusplus.com/reference/cassert/assert/

Clean:

make clean

rm *.o

make run ARGS=1

gcc  -I ./include -c ./src/main.c

g++  -I ./include -c ./src/reciprocal.cpp

g++  main.o reciprocal.o -o reciprocal

./reciprocal 1

The reciprocal of 1 is 1

make run ARGS=0

./reciprocal 0

reciprocal: ./src/reciprocal.cpp:7: double reciprocal(int): Assertion `i != 0' failed.

make: *** [Makefile:8: run] Aborted (core dumped)

make clean

rm *.o

make run CFLAGS="-D NDEBUG=3 -O2" ARGS=1

S="-D NDEBUG=3 -O2" ARGS=1

gcc -D NDEBUG=3 -O2 -I ./include -c ./src/main.c

g++ -D NDEBUG=3 -O2 -I ./include -c ./src/reciprocal.cpp

g++ -D NDEBUG=3 -O2 main.o reciprocal.o -o reciprocal

./reciprocal 1

The reciprocal of 1 is 1

make run ARGS=0

./reciprocal 0

The reciprocal of 0 is inf

make clean

rm *.o

*********************************************************************************

*********************************************************************************

*********************************************************************************

*********************************************************************************

*********************************************************************************

debug.txt     ALP, p. 23-24

make CFLAGS=-g

gcc -g -I ./include -c ./src/main.c

g++ -g -I ./include -c ./src/reciprocal.cpp

g++ -g main.o reciprocal.o -o reciprocal

gdb reciprocal

(gdb) run 0

// reciprocal: ./src/reciprocal.cpp:7: double reciprocal(int):

// Assertion `i != 0' failed.

// Program received signal SIGABRT, Aborted.

(gdb) where

#0  ...

#1  ...

#2  assertion=... "i != 0", 

    file=... "./src/reciprocal.cpp", line=7, 

#3  function=... "double reciprocal(int)")

#4  in reciprocal (i=0) at ./src/reciprocal.cpp:7

#5  in main (argc=2, argv=...) at ./src/main.c:17

(gdb) up

#1 ...

(gdb) up 3

#4 ...

(gdb) print i

// $1 = 0

(gdb) down

#3 ...

(gdb) down 2

#1 ...

(gdb) next

// Program terminated with signal SIGABRT, Aborted.

// The program no longer exists.

(gdb) break main

// Breakpoint 1, main (argc=..., argv=...) at ./src/main.c:6

(gdb) break reciprocal

// Breakpoint 2 at ...: file ./src/reciprocal.cpp, line 5.

(gdb) run 0

// Breakpoint 1, main

(gdb) next

// if (argc != 2)

(gdb) next

// i = atoi (argv[1]);

(gdb) next

// printf ("The reciprocal of %d is %g\n", i, reciprocal (i));

(gdb) step

// Breakpoint 2, reciprocal

(gdb) step

// assert (i != 0);

(gdb) step

// __GI___assert_fail (assertion=... "i != 0", 

//  file=... "./src/reciprocal.cpp", line=7, 

//  function=... "double reciprocal(int)")

(gdb) next

// reciprocal: ./src/reciprocal.cpp:7: double reciprocal(int):

// Assertion `i != 0' failed.

// Program received signal SIGABRT, Aborted.

(gdb) next

// Program terminated with signal SIGABRT, Aborted.

// The program no longer exists.

(gdb) next

// The program is not being run.

(gdb) q // quit debugger

make clean

rm *.o

Advanced_Linux_Programming                                 Back_to_Top                              Chapter_2