malloc function

Rosmayati · #1 18-May-2004, 02:32

I've tried to use malloc function for dynamic memory allocation since i will be using very large input data.unfortunately, i've got the error like below.could anyone tell me how to solve the error?

Cannot convert void * to int *

Max Payne · #2 18-May-2004, 03:13

Hi Rosmayati,

just like your other question, you posted the error but not the source codes.. in order to help you figure out what the problem is, you should post the codes that is causing you the error..

Rosmayati · #3 18-May-2004, 04:00

this is the source code

CPP / C++ / C Code:

#include <stdio.h>
#include <stdlib.h> /* required for the malloc and free functions */

int main() {
  int number;
  int *ptr;
  int i;

  printf("How many ints would you like store? ");
  scanf("%d", &number);

  ptr = malloc(number*sizeof(int)); /* allocate memory */
 
  if(ptr!=NULL) {
    for(i=0 ; i<number ; i++) {
      *(ptr+i) = i;
    }

    for(i=number ; i>0 ; i--) {
      printf("%d\n", *(ptr+(i-1))); /* print out in reverse order */
    }

    free(ptr); /* free allocated memory */
    return 0;
  }
  else {
    printf("\nMemory allocation failed - not enough memory.\n");
    return 1;
  }
}

Max Payne · #4 18-May-2004, 04:26

the line here is the problem:

CPP / C++ / C Code:

ptr = malloc(number*sizeof(int)); /* allocate memory */

malloc return a void* and you cannot change it to ptr which is an int*.
try casting like this to correct it:

CPP / C++ / C Code:

ptr = (int*)malloc(number*sizeof(int)); /* allocate memory */

WaltP · #5 18-May-2004, 17:15

I believe the problem is you are compiling your program as a C++ file, not a C file. In C you are not supposed to specify the type returned from malloc(). When I compile it, your original code works fine. When I compile it with a .cpp extension, I get the same error you do.

Look at your compiler's switches and add the switch that specifies C-compilation. Or if your file ends in .cpp, change it to .c

Rosmayati · #6 18-May-2004, 21:08

Okey, thanks for the solution. really appreciate it..

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