Sean Kelly wrote:
> I suppose the obvious question here is: what if I want to create a mutex
> in D?

Why do you need volatile for that?

Walter Bright wrote:
> Sean Kelly wrote:
>> I suppose the obvious question here is: what if I want to create a mutex
>> in D?
> 
> Why do you need volatile for that?

To restrict compiler optimizations performed on the code.


Sean

Sean Kelly wrote:
> Walter Bright wrote:
>> Sean Kelly wrote:
>>> I suppose the obvious question here is: what if I want to create a mutex
>>> in D?
>>
>> Why do you need volatile for that?
> 
> To restrict compiler optimizations performed on the code.

The optimizer won't move global or pointer references across a function call boundary.

Walter Bright wrote:

> Sean Kelly wrote:
>> Walter Bright wrote:
>>> Sean Kelly wrote:
>>>> I suppose the obvious question here is: what if I want to create a mutex in D?
>>>
>>> Why do you need volatile for that?
>> 
>> To restrict compiler optimizations performed on the code.
> 
> The optimizer won't move global or pointer references across a function call boundary.

Is that true for all compiler's or only DigitalMars ones?

-- 
Lars Ivar Igesund
blog at http://larsivi.net
DSource, #d.tango & #D: larsivi
Dancing the Tango

Walter Bright wrote:
> Sean Kelly wrote:
>> Walter Bright wrote:
>>> Sean Kelly wrote:
>>>> I suppose the obvious question here is: what if I want to create a mutex
>>>> in D?
>>>
>>> Why do you need volatile for that?
>>
>> To restrict compiler optimizations performed on the code.
> 
> The optimizer won't move global or pointer references across a function call boundary.

Even if the function is inlined?


Sean

Lars Ivar Igesund wrote:
> Walter Bright wrote:
> 
>> Sean Kelly wrote:
>>> Walter Bright wrote:
>>>> Sean Kelly wrote:
>>>>> I suppose the obvious question here is: what if I want to create a
>>>>> mutex in D?
>>>> Why do you need volatile for that?
>>> To restrict compiler optimizations performed on the code.
>> The optimizer won't move global or pointer references across a function
>> call boundary.
> 
> Is that true for all compiler's or only DigitalMars ones?

DM ones certainly. Others, I don't know about.

Sean Kelly wrote:
> Walter Bright wrote:
>> Sean Kelly wrote:
>>> Walter Bright wrote:
>>>> Sean Kelly wrote:
>>>>> I suppose the obvious question here is: what if I want to create a mutex
>>>>> in D?
>>>>
>>>> Why do you need volatile for that?
>>>
>>> To restrict compiler optimizations performed on the code.
>>
>> The optimizer won't move global or pointer references across a function call boundary.
> 
> Even if the function is inlined?

No, but a mutex involves an OS call. Inlining is also easily prevented.

Walter Bright wrote:

> Lars Ivar Igesund wrote:
>> Walter Bright wrote:
>> 
>>> Sean Kelly wrote:
>>>> Walter Bright wrote:
>>>>> Sean Kelly wrote:
>>>>>> I suppose the obvious question here is: what if I want to create a mutex in D?
>>>>> Why do you need volatile for that?
>>>> To restrict compiler optimizations performed on the code.
>>> The optimizer won't move global or pointer references across a function call boundary.
>> 
>> Is that true for all compiler's or only DigitalMars ones?
> 
> DM ones certainly. Others, I don't know about.

So you are saying that you're removing (or not going to implement) a feature due to a restriction in the DM optimizer?

-- 
Lars Ivar Igesund
blog at http://larsivi.net
DSource, #d.tango & #D: larsivi
Dancing the Tango

Walter Bright wrote:
> Sean Kelly wrote:
>> Walter Bright wrote:
>>> Sean Kelly wrote:
>>>> Walter Bright wrote:
>>>>> Sean Kelly wrote:
>>>>>> I suppose the obvious question here is: what if I want to create a mutex
>>>>>> in D?
>>>>>
>>>>> Why do you need volatile for that?
>>>>
>>>> To restrict compiler optimizations performed on the code.
>>>
>>> The optimizer won't move global or pointer references across a function call boundary.
>>
>> Even if the function is inlined?
> 
> No, but a mutex involves an OS call. Inlining is also easily prevented.

An OS call isn't always involved.  See, for example: http://en.wikipedia.org/wiki/Futex.


Sean

Reply to Walter,

> No, but a mutex involves an OS call. Inlining is also easily
> prevented.
> 

using atomic ASM ops a (single process) mutex can be implemented with no OS interaction at all.