Question

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include<time.h>

void insertionSort(int arr[], int n);
void merge(int a[], int l1, int h1, int h2);

void mergeSort(int a[], int l, int h)
{
int i, len=(h-l+1);
//Using insertion sort for small sized array
if (len<=5)
{
insertionSort(a+l, len);
return;
}
pid_t lpid,rpid;
lpid = fork();
if(lpid<0)
{
//Lchild proc not created
perror("Left Child Proc. not created\n");
_exit(-1);
}
else if (lpid==0)
{
mergeSort(a,l,l+len/2-1);
_exit(0);
}
else
{
rpid = fork();
if (rpid<0)
{
// Rchild proc not created
perror("Right Child Proc. not created\n");
_exit(-1);
}
else if(rpid==0)
{
mergeSort(a,l+len/2,h);
_exit(0);
}
}
int status;
//Wait for child processes to finish
waitpid(lpid, &status, 0);
waitpid(rpid, &status, 0);
//merge the sorted svbarrays
merge(a, l, l+len/2-1, h);
}

/* Function to sort an array using Insertion sort*/
void insertionSort(int arr[], int n)
{
int i, key, j;
for(i = 1; i < n; i++)
{
key = arr[i];
j = i - 1;
/* Move elements of arr[0..i-1], that are greater than key, to one position ahead of their current position */
while(j >= 0 && arr[j] > key)
{
arr[j+1] = arr[j];
j = j -1;
}
arr[j+1] = key;
}
}

//Method to merge sorted subarrays
void merge(int a[], int l1, int h1, int h2)
{
// We Can directly copy the sorted elements in the final array, no need for a temporary sorted array.
int count=h2-l1+1;
int sorted[count];
int i=l1, k=h1+1, m=0;
while (i<=h1 && k<=h2)
{
if (a[i]<a[k])
sorted[m++]=a[i++];
else if (a[k] < a[i])
sorted[m++] = a[k++];
else if (a[i] == a[k])
{
sorted[m++] = a[i++];
sorted[m++] = a[k++];
}
}
while (i<=h1)
sorted[m++] = a[i++];

while (k<=h2)
sorted[m++] = a[k++];

int arr_count = l1;
for( i = 0; i<count; i++, l1++)
a[l1] = sorted[i];
}

// To check if array is actually sorted or not
void isSorted(int arr[], int len)
{
if(len == 1)
{
printf("Sorting done successfully\n");
return;
}
int i;
for(i = 1; i<len; i++)
{
if (arr[i]<arr[i-1])
{
printf("Sorting not done\n");
return;
}
}
printf("Sorting done successfully\n");
return;
}

// To fill random values in array for testing purpose
void fillData(int a[], int len)
{
// Create random arrays
int i;
for (i=0; i<len; i++)
a[i] = rand();
return;
}

// Driver code
int main()
{
int shmid;
key_t key = IPC_PRIVATE;
int *shm_array;
int length = 128;
//Calculate segment length
size_t SHM_SIZE = sizeof(int)*length;
// Create the segment.
if ((shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0666)) < 0)
{
perror("shmget");
_exit(1);
}

// Now we attach the segment to our data space.
if ((shm_array = shmat(shmid, NULL, 0)) == (int *) -1)
{
perror("shmat");
_exit(1);
}

// Create a random array of given length
srand(time(NULL));
fillData(shm_array, length);

// Sort the created array
mergeSort(shm_array, 0, length-1);

//Check 1f array Is sorted or not
isSorted(shm_array, length);

/* Detach from the shared memory now that we are done using it. */
if (shmdt(shm_array) == -1)
{
perror("shmdt");
_exit(1);
}
/* Delete the shared memory segment. */
if (shmctl(shmid, IPC_RMID, NULL) == -1)
{
perror("shmctl");
_exit(1);
}
return 0;
}

WHAT IS WRONG WITH THIS CODE??

ERROR IM GETTING :

error: invalid conversion from ‘void*’ to ‘int*’ [-fpermissive]
154 | if ((shm_array = shmat(shmid, NULL, 0)) == (int *) -1)
| ~~~~~^~~~~~~~~~~~~~~~
| |
| void*

Answer 1

PLEASE FIND THE ANSWER(S) and EXPLANATION BELOW.

The question says there is a type conversion error.

error: invalid conversion from ‘void*’ to ‘int*’ [-fpermissive]
154 | if ((shm_array = shmat(shmid, NULL, 0)) == (int *) -1)
| ~~~~~^~~~~~~~~~~~~~~~
| |
| void*

But, there is no error in the code.

I am able to run the code as we can see it below.

For the reference, I am attaching some piece of code to print the array.

==========// print the data once
printf("The sorted array is: ");
for(int i=0;i<length;i++)
{
printf("%d, ",shm_array[i]);
}

===========

168 issorted(shm_array, length); 169 // print the data once 170 printf("The sorted array is: "); 171 for(int i=0;i<length; i++) 172 { 173 printf("%d, ", shm_array[i]); 174 } input Sorting done successfully The sorted array is: 1237315, 26071894, 29281474, 41569255, 55724756, 60068393, 65619223, 67891640, 92129742, 133510863, 148374162, 149611477, 212304629, 212660832, 258555107, 291184057, 294414451, 298627010, 308237470, 310912457, 347372484, 395651658, 396934941, 402775556, 427575722, 435047514, 444958940, 446196255, 454402266, 460539773, 466051964, 503844890, 509566736, 511482547, 556079529, 567207304, 581373144, 587696409, 595807732, 606494667, 610654618, 623060431, 650981737, 664419484, 702706785, 737435722, 739348158, 743585950, 755825033, 773166633, 835365061, 841354755, 856167666, 864453797, 869979436, 905741300, 926170457, 969371291, 983477509, 987997633, 1028521447, 1033259268, 1056395176, 1074828523, 1134999816, 1146491543, 1173993657, 1183922435, 1189782205, 1209200961, 1 215562912, 1222929123, 1232300002, 1285178475, 1306181751, 1310331768, 1311904562, 1320721302, 1337976456, 1366250144, 1372146847, 1377517308, 1382702501, 1387574191, 1418525023, 1432215240, 1437726 568, 1443864075, 1468306782, 1489429626, 1492307978, 1493864028, 1500501619, 1566120842, 1586621644, 1608827991, 1617476013, 1621845599, 1644876073, 1648888913, 1699631706, 1703536135, 1705808552, 1 709605755, 1733757473, 1735677649, 1738278526, 1779637442, 1785589937, 1786722429, 1804776485, 1815695628, 1833583741, 1841976457, 1854201689, 1892128834, 1921358158, 1931375920, 1944449132, 1956259 410, 1973982108, 2035324154, 2068317182, 2070760573, 2088597698, 2102053065, 2116479197, 2141346141, ... Program finished with exit code o Press ENTER to exit console.

Please run it properly.

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