Question

Create a function, void allocate_mem(unsigned int** input_one, unsigned int** input_two, unsigned long int** output, int num_ints) in C.

This function allocates enough memory to the three arrays to store num_ints elements each.

This function should exit with EXIT_FAILURE if the program fails to allocate the memory.

input parameters:

unsigned int* input_one

unsigned int* input_two

unsigned long int* output

int num_ints

return parameters:

none

Do NOT hard code the size of the unsigned (long) integer arrays

Answer 1

Two things:

1. It is NOT possible to explicitly check whether a pointer has been allocated memory or not so we'll check by allocating values and displaying.
2. Secondly, we don't have exception handling (try..catch) in C so we'll use a #define workaround.

//Program in C

#include <setjmp.h>
#include <stdlib.h>
#include <stdio.h>

#define FALSE 0
//define try block for exception handling simulation
#define TRY_BLOCK do{ jmp_buf buffer; if( setjmp(buffer) == FALSE ){
//define catch block for exception handling simulation
#define CATCH_BLOCK } else {
//define exit block for exception handling simulation
#define EXIT_BLOCK } }while(FALSE)

//function to allocate memory
void allocate_mem(unsigned int** input_one, unsigned int** input_two,
unsigned long int** output, int num_ints)
{
//start try block
TRY_BLOCK
{
*input_one = (unsigned int*)malloc(num_ints * sizeof(input_one));
*input_two = (unsigned int*)malloc(num_ints * sizeof(input_one));
*output = (unsigned long int*)malloc(num_ints * sizeof(input_one));
}
//exit using catch block
CATCH_BLOCK
{
exit(EXIT_FAILURE);
}
EXIT_BLOCK;
//assign values to arrays
for(int i=0; i<num_ints; i++)
*(*input_one+ i) = i*1;
for(int i=0; i<num_ints; i++)
*(*input_two+ i) = i*2;
for(int i=0; i<num_ints; i++)
*(*output+ i) = i*3;
}

//main function
int main()
{
//declare pointers to arrays
unsigned int *ptr1,*ptr2;
unsigned long *ptr3;
//declare size variable
int size;
//get size of array
printf("Enter Size: ");
scanf("%d", &size);
//call the function to allocate memory
allocate_mem( &ptr1 , &ptr2 , &ptr3 , size );
//print the arrays
printf("\nArray 1 is: ");
for(int i=0; i<size ;i++)
printf("%d\t", ptr1[i]);
printf("\nArray 2 is: ");
for(int i=0; i<size ;i++)
printf("%d\t", ptr2[i]);
printf("\nArray 3 is: ");
for(int i=0; i<size ;i++)
printf("%ld\t", ptr3[i]);
free(ptr1);
free(ptr2);
free(ptr3);
return 0;
}

//Output

Enter Size: 6
Array 1 is: 0   1   2   3   4   5  
Array 2 is: 0   2   4   6   8   10  
Array 3 is: 0   3   6   9   12   15  

//Screenshot of Output & Code (For reference to indentation)

> Run C++10 co c o S Reset Copy Copy * > Run+URL (Generates URL as C++ C++14 C# 42 Java Perl PHP Time(sec): 0 49 Memory(MB): 1.5225436108398 Python Python 3 Shortcuts 40 int main() 41 - { 7/declare pointers to arrays unsigned int *ptri, *ptr2; unsigned long *ptr3; 45 //declare size variable 46 int size; //get size of array printf("Enter Size: "); scanf("%d", &size); //call the function to allocate memory allocate_mem( &ptri , &ptr2 , &ptr3 , size //print the arrays printf("\nArray 1 is: "); for(int i=0; i<size ; i++) printf("%d\t", ptr1[i]); printf("\nArray 2 is: "); for(int i=0; i<size ; i++) printf("%d\t", ptr2[i]); printf("\nArray 3 is: "); for(int i=0; i<size ; i++) printf("%d\t", ptr3[i]); free(ptri); 63 free(ptr2); free(ptr); return 0; 66 Output: Copy Scala HTML & Enter Size: Array 1 is: 0 Array 2 is: 6 Array 3 is: 1 2 3 4 6 6 9 8 12 10 15