converting D's string to use with C API with unicode

[tsbockman]

On Saturday, 5 December 2020 at 21:55:13 UTC, Jack wrote:
> my code now look like this, still there's a memory corrupt. 
> Could anyone help point out where is it?
>
> ...
>
>> foreach(i; 0..output.length) {
>>     wstring ws;
>>     transcode(output[i], ws);
>>     auto s = malloc(ws.length + 1);
>>     if(!s) {
>>         onOutOfMemoryError();
>>     }
>>     memcpy(s, ws.ptr, ws.length);

`ws.length` is the length in `wchar`s, but `memcpy` expects the 
size in bytes. (This is because it takes `void*` pointers as 
inputs, and so does not know the element type or its size.)

Also, I think you need to manually zero-terminate `s`. You 
allocate space to do so, but don't actually use it. (I believe 
that transcode will only zero-terminate the destination if the 
source argument is already zero-terminated.)

>>     r.output[i] = cast(wchar*)s;
>> }