pointers - Type conversion issue in C# -

i'm trying (originally comes here) heap , pointer on c# console project. , program looks this:

using system; using system.collections.generic; using system.linq; using system.text; using system.threading.tasks; using system.runtime.interopservices;  public class win32 { [dllimport("user32.dll", charset = charset.auto)] public static extern intptr malloc(int size);  [dllimport("user32.dll", charset = charset.auto)] public static extern int free(intptr region); //change intptr befroe free method int ---update--- }  public class program {     public unsafe void heap()     {         int* num1, num2, answer;         num1 = win32.malloc(sizeof(int));         *num1 = 999; // 999 should value stored @ pointer num1 refers          num2 = win32.malloc(sizeof(int));         *num2 = 1; // 1 should value stored @ pointer num2 refers          answer = win32.malloc(sizeof(int));         *answer = *num1 + *num2; // 1000 should value of pointer answer's reference          console.writeline(*answer); // 1000?         win32.free(num1);         win32.free(num2);         win32.free(answer);     } } 

after debugging, got error message says:

error 1 cannot implicitly convert type 'system.intptr' 'int*'. explicit conversion exists (are missing cast?)

error cs1502: best overloaded method match 'win32.free(system.intptr)' has invalid arguments  error cs1503: argument 1: cannot convert 'int*' 'system.intptr' 

my questions here why can't use intptr before malloc , free, since both method return void? changes should make on codes? thank help.

---update---

change: public static extern intptr free(int hwnd); public static extern int free(intptr region); , free(*num) free(num)

gives 'cs1502' , 'cs1503' 2 errors.

---second update--- c# deal heap thing automatically. there no equivalent of malloc in c#. it's dead end. t_t

a few mistakes:

in c/c++

void * malloc(int sizetoallocate); int free(void * region); 

you pass free value returned malloc. imports should be:

[dllimport("user32.dll", charset = charset.auto)] public static extern intptr malloc(int size);   [dllimport("user32.dll", charset = charset.auto)] public static extern int free(intptr region);  

and consequently freeing code should become:

 var num1ptr = win32.malloc(sizeof(int));  int * num1 = (int*) num1ptr.topointer();   ...   var num2ptr = win32.malloc(sizeof(int));  int * num2 = (int*) num2ptr.topointer();   ...   var answerptr = win32.malloc(sizeof(int));  int * answer = (int*) answerptr.topointer();   ...   win32.free(num1ptr);  win32.free(num2ptr);  win32.free(answerptr);