how to free memory

[kfaday]

I've got a char array

char *vec;

and i allocate memory for a number of elemets

vec = (char*) malloc ((sizeof(char))*(number_of_elemets));

i do that in main.
then i call a free function

free_mem (vec);

the function code is:

void free_mem (char *vec,number_of _elements)
{   
        for (i=0;i<(number_of _elements);i++)
	{
                 	free (vec[i]);
	}
}

it gives me errors
what's wrong?
thanks!!

[CBasicNet]

free() takes in a address as argument

you can just do this,

free(vec);

[kfaday]

i tried but it gave me a runtime error when it gets to free (vec)

NOTE: i can only use ansi c, that's why i use malloc instead of new

[Paul McKenzie]

Originally posted by kfaday

void free_mem (char *vec,number_of _elements)
{   
        for (i=0;i<(number_of _elements);i++)
       {
               	free (vec[i]); // Wrong
      }
}

This is totally wrong.

You call free() on the value returned by malloc(). You are not doing this in the code you're showing -- you're calling free() on each of the characters, which is invalid and leads to undefined behavior.

free(vec);

That's it.

i tried but it gave me a runtime error when it gets to free (vec)

Then you are corrupting the heap somewhere else in your program. You will see that there is nothing wrong when you do this:

#include <stdlib.h>

int main()
{
   char *vec;
   int number_of_elements = 100;
   vec = (char*) malloc ((sizeof(char))*(number_of_elemets));
   free(vec);
}

Do you get a runtime error when you run this program? If not, it is what you're doing in your program between the calls to malloc and free that is causing the problem.

Regards,

Paul McKenzie

[cma]

You don't need the loop, just

free(vec)

.

[Andreas Masur]

Well..just out of curiosity...is there any special need that you are using a C character array (like limited to C programming)? Otherwise, I would suggest using one of the C++ standard classes 'vector' or 'string' (depending on what your array will contain) which contains their own memory management...

[Rabelo]

just do:

void free_mem (char *vec)
{   	
  free (vec);
}

then free_mem is not necessary..
You´re not allocating an array. You´re allocating a continuos block of memory so you have to deallocating it once.

Rabelo

[kfaday]

i was writing one position over what i reserved
i reserved x places and i wrote the x+1 place
now i can do free (vec) and it works
thanks

[Andreas Masur]

Originally posted by kfaday
i was writing one position over what i reserved
i reserved x places and i wrote the x+1 place
now i can do free (vec) and it works
thanks

And that is one of the best reasons for using the standard 'vector' class instead...as long as you are programming in C++...