How to get mbstowcs_s result variable return from function

Question

I made a post yesterday and screwed it up a bit. I still got a great answer, I did some more work, but I remain having an issue. how do I get the "return_address" from mbstowcs_s into my main dir_path?

.h file:

void* get_absolute_path(char *directory, u16 *return_address, int len);

Function .c file:

void* get_absolute_path(char *directory, u16 *return_address, int len) {
    u64 dest;
    int errorDir = mbstowcs_s(&dest, return_address, len, directory, len);
    return return_address;
}

main, function caller:

int main(void) {

    char dir[] = "C:\\Windows\\";
    u16 return_address[268];
    u16 dir_path = get_absolute_path(dir, return_address, 268);

    return true;
}

I get a clang error:

fatal error LNK1120: 1 unresolved externals
clang: error: linker command failed with exit code 1120 (use -v to see invocation)
make: *** [link] Error 1120
Error:2

---

BUT If I remove the "*" from the void's, I get a different error:

error: void function 'get_absolute_path' should not return a value
      [-Wreturn-type]
    return return_address;

But this thing is incredible unstable! If I remove the "*" from void, run it, and than re-type the * after the voids as posted, I get a different error this time:

 warning: incompatible pointer to integer conversion
      initializing 'u16' (aka 'unsigned short') with an expression of type 'void *'
      [-Wint-conversion]
    u16 dir_path = get_absolute_path(dir, return_address, 268);
        ^          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Do I run it again a 2nd time, than I get the original error again: I restarted the pc, but this unstable error thing keeps happening.

u16 is unsigned short. u64 is unsigned long long.

Your help is greatly appreciated, thank you.

I'm new to C and I understand the point thing on paper, in practise I have some issues with it. So I played around with making pointers at different places and so on. I very much would like to make this work without allocating.

Adding a "*" before dir_path:

u16 dir_path = get_absolute_path(dir, return_address, 268);

to:

u16 *dir_path = get_absolute_path(dir, return_address, 268);

Gives the error:

fatal error LNK1120: 1 unresolved externals
clang: error: linker command failed with exit code 1120 (use -v to see invocation)
make: *** [link] Error 1120

u16

Changing void* tot u16, I get the error:

warning: incompatible pointer to integer conversion returning
      'u16 *' (aka 'unsigned short *') from a function with result type 'u16'
      (aka 'unsigned short'); dereference with * [-Wint-conversion]
    return return_address;
           ^~~~~~~~~~~~~~

So adding the "*" at return,

return *return_address;

:

 fatal error LNK1120: 1 unresolved externals
clang: error: linker command failed with exit code 1120 (use -v to see invocation)
make: *** [link] Error 1120
Error:2

u16*

Changing the void* tot u16*:

warning: incompatible pointer to integer conversion
      initializing 'u16' (aka 'unsigned short') with an expression of type 'u16 *'
      (aka 'unsigned short *'); dereference with * [-Wint-conversion]
    u16 dir_path = get_absolute_path(dir, return_address, 268);

So as stated, now I add the "*" :

u16 dir_path = *get_absolute_path(dir, return_address, 268);

And from this I get:

 fatal error LNK1120: 1 unresolved externals
clang: error: linker command failed with exit code 1120 (use -v to see invocation)
make: *** [link] Error 1120

    ^          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~