Thread: Dynamically sized array function behavior

Notice if you use the same pointer as an argument and return to realloc() call you can end up with a memory leakage if realloc() fails. It is wise to use different pointers. Your code, changed a little bit:

Code:

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

int push_int( int **array, size_t *counter, int value )
{
  int *p;

  if ( ! ( p = realloc( *array, ( *counter + 1 ) * sizeof value ) ) )
    return 0;

  p[( *counter )++] = value;
  *array = p;  // update the pointer!

  return 1;
}

int main( int argc, char *argv[] )
{
  int *array;
  char *line;
  size_t len, counter;
  int number;

  if ( !( array = malloc( sizeof * array ) ) )
  {
    fputs( "ERROR allocating initial array.\n", stderr );
    return EXIT_FAILURE;
  }

  line = NULL;
  len = 0;
  counter = 0;

  // getline() will allocate a buffer for the line. This buffer must be freed
  // before calling getline() again!
  while ( getline( &line, &len, stdin ) != -1 )
  {
    if ( sscanf( line, "%d", &number ) != 1 )
    {
      fputs( "ERROR geting integer value.\n", stderr );
      free( line );
      free( array );
      return EXIT_FAILURE;
    }

    number = atoi( line );

    // free allocated line and prepare for next read.
    free( line );
    line = NULL;
    len = 0;

    if ( ! push_int( &array, &counter, number ) )
    {
      fputs( "ERROR pushing value.\n", stderr );
      free( array );
      return EXIT_FAILURE;
    }
  }

  // ... dosomething with the array here...
  // ...


  // Finally free the array and return with success.
  free( array );

  return EXIT_SUCCESS;
}