Problems with Mutex

[Neven via Digitalmars-d-learn]

On Sunday, 26 October 2014 at 22:21:17 UTC, Damian wrote:
> On Sunday, 26 October 2014 at 22:14:25 UTC, Neven wrote:
>> I'm trying to use Mutex from core.sync.mutex; but when I try 
>> to initialize it at compile time this error pops up:
>>
>> Error: constructor core.sync.mutex.Mutex.this 
>> core.sync.mutex.Mutex cannot be constructed at compile time, 
>> because the constructor has no available source code
>>
>> So I try to initialize it at run time but whenever I use that 
>> mutex in code (via synchronized blocks) I get segmetation 
>> faults (SIGSEGV).
>>
>> Code here: http://pastebin.com/Z8Yj2kwY
>
> Try
> __gshared Mutex mutex;

Thanks, that works now; but why?

Why cannot I globally have auto mutex = new Mutex? And why it 
works now when I put __gshared?