Malloc question,... again!

**audinue** · 10-28-2008

Please take a look on this...

Code:

#include <stdlib.h> //malloc, free, itoa
#include <stdio.h>  //printf

#define POSSIBLE_MAXIMUM_INT_VALUE 10

char *IntToStr(int value)
{
  char *buffer = malloc(POSSIBLE_MAXIMUM_INT_VALUE);
  itoa(value, buffer, 10);
                   // ^-- base 10
  return buffer;
}

int main()
{
  int value = 2008;

  printf("%s\n", IntToStr(value));  // >> 2008
  //Question: Should we deallocate the returned value?

  //do we need to get the buffer first??

  //get the returned value
  char *buffer = IntToStr(value);

  //do something with buffer
  printf("%s\n", buffer);           // >> 2008

  //deallocate the buffer
  free(buffer);
}

Thanks in advance V(^_^)V

**zacs7** · 10-28-2008

There is really only 1 question... and the answer is yes.

Don't forget to check the return value of malloc() before using it.

**audinue** · 10-28-2008

Then we should warn users to deallocate our returned value in our documentation... *sob*

**zacs7** · 10-28-2008

You should provide some sort of "deallocation" function. Since the users (or in future; you) may use some other function other than free() (ie you didn't use malloc or some such).

This ensures that your pointer returned from malloc() will be free'd by its direct sister free(). IMO, a better method in this case is to have the user pass in a char pointer to where they want the data to go;

Code:

#include <stdio.h>

int IntToStr(int value, char * str, size_t n)
{
   /* you can now do error checking and return a result (ie, 0 pass, non-zero fail) */

}

int main(void)
{
   char x[6];

   if(IntToStr(50, x, sizeof(x)) != 0)
   {
      printf("error!\n");
   }
   return 0;
}

**audinue** · 10-28-2008

Thanks zacs7!

I think I should change "the way" to develop a function.

**Elysia** · 10-28-2008

In a nutshell, because you return a pointer which points to malloced memory, you must free it.
For every time you call malloc, you call free.
What did you think there was an exception or were confused?

**audinue** · 10-28-2008

What did you think there was an exception or were confused?

Well, I just curious about this statement:

Code:

printf("%s\n", IntToStr(value));

A wrong way to make a function in C. (~*.*~)"

**Elysia** · 10-28-2008

A wrong way to make a function? Huh?

**~~master5001~~** · 10-28-2008

It is the wrong way to format something that is supposed to return an integer.

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