Low-level programming & Algorithm - Hatching out

C - Preprocessor

Resources

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Read or watch:

Understanding C program Compilation Process
Object-like Macros
Macro Arguments
Pre Processor Directives in C
The C Preprocessor
Standard Predefined Macros
include guard
Common Predefined Macros

Learning Objectives

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General

• What are macros and how to use them
• What are the most common predefined macros
• How to include guard your header files
  
  

Requirements

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General

• Allowed editors: vi, vim, emacs
• All your files will be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89
• All your files should end with a new line
• Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl
• You are not allowed to use global variables
• No more than 5 functions per file
• The only C standard library functions allowed are malloc, free and exit. Any use of functions like printf, puts, calloc, realloc etc… is forbidden
• All your header files should be include guarded

More Info

You do not have to learn about calloc and realloc.

Tasks

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0. Object-like Macro

Create a header file that defines a macro named SIZE as an abbreviation for the token 1024.

pie@ubuntu:~/0x0c. macro, structures$ cat 0-main.c
#include "0-object_like_macro.h"
#include "0-object_like_macro.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    int s;

    s = 98 + SIZE;
    printf("%d\n", s);
    return (0);
}
pie@ubuntu:~/0x0c. macro, structures$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 0-main.c -o a
pie@ubuntu:~/0x0c. macro, structures$ ./a 
1122
pie@ubuntu:~/0x0c. macro, structures$ 

Repo:

• GitHub repository: alx-low_level_programming
• Directory: 0x0D-preprocessor
• File: 0-object_like_macro.h
  

1. Pi

Create a header file that defines a macro named PI as an abbreviation for the token 3.14159265359.

pie@ubuntu:~/0x0c. macro, structures$ cat 1-main.c
#include "1-pi.h"
#include "1-pi.h"
#include <stdio.h>

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    float a;
    float r;

    r = 98;
    a = PI * r * r;
    printf("%.3f\n", a);
    return (0);
}
pie@ubuntu:~/0x0c. macro, structures$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 1-main.c -o b
pie@ubuntu:~/0x0c. macro, structures$ ./b
30171.855
pie@ubuntu:~/0x0c. macro, structures$ 

Repo:

• GitHub repository: alx-low_level_programming
• Directory: 0x0D-preprocessor
• File: 1-pi.h
  

2. File name

Write a program that prints the name of the file it was compiled from, followed by a new line.

• You are allowed to use the standard library

  pie@ubuntu:~/0x0c. macro, structures$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 2-main.c -o c
  pie@ubuntu:~/0x0c. macro, structures$ ./c 
  2-main.c
  pie@ubuntu:~/0x0c. macro, structures$ cp 2-main.c 02-main.c
  pie@ubuntu:~/0x0c. macro, structures$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 02-main.c -o cc
  pie@ubuntu:~/0x0c. macro, structures$ ./cc
  02-main.c
  pie@ubuntu:~/0x0c. macro, structures$ 

Repo:

• GitHub repository: alx-low_level_programming
• Directory: 0x0D-preprocessor
• File: 2-main.c
  

3. Function-like macro

Write a function-like macro ABS(x) that computes the absolute value of a number x.

pie@ubuntu:~/0x0c. macro, structures$ cat 3-main.c
#include <stdio.h>
#include "3-function_like_macro.h"
#include "3-function_like_macro.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    int i;
    int j;

    i = ABS(-98) * 10;
    j = ABS(98) * 10;
    printf("%d, %d\n", i, j);
    return (0);
}
pie@ubuntu:~/0x0c. macro, structures$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 3-main.c -o d
pie@ubuntu:~/0x0c. macro, structures$ ./d 
980, 980
pie@ubuntu:~/0x0c. macro, structures$ 

Repo:

• GitHub repository: alx-low_level_programming
• Directory: 0x0D-preprocessor
• File: 3-function_like_macro.h
  

4. SUM

Write a function-like macro SUM(x, y) that computes the sum of the numbers x and y.

pie@ubuntu:~/0x0c. macro, structures$ cat 4-main.c
#include <stdio.h>
#include "4-sum.h"
#include "4-sum.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    int s;

    s = SUM(98, 1024);
    printf("%d\n", s);
    return (0);
}
pie@ubuntu:~/0x0c. macro, structures$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 4-main.c -o e
pie@ubuntu:~/0x0c. macro, structures$ ./e 
1122
pie@ubuntu:~/0x0c. macro, structures$ 

Repo:

• GitHub repository: alx-low_level_programming
• Directory: 0x0D-preprocessor
• File: 4-sum.h