A weird example of .toUTF16z concatination side-effects in wcsncat

[Stanislav Blinov]

On Thursday, 7 April 2022 at 10:50:35 UTC, BoQsc wrote:

> 	wchar_t* clang_string         = cast(wchar_t *)"AAAAAAAAAA";

You're witnessing undefined behavior. "AAAAAAAAAA" is a string 
literal and is stored in the data segment. Mere cast to wchar_t* 
does not make writing through that pointer legal. Moreover, even 
if it was legal to write through it, that alone wouldn't be 
sufficient. From documentation of `wcsncat`:

> The behavior is undefined if the destination array is not large 
> enough for the contents of both str and dest and the 
> terminating null wide character.

`wcsncat` does not allocate memory, it expects you to provide a 
sufficiently large mutable buffer. For example, like this:

```d
     // ...
     auto cls = new wchar_t[256];
     cls[] = 0;
     cls[0..10] = 'A';
     wchar_t* clang_string = cls.ptr;
     // ...
```