I want to add a Phobos module with template mixins for common idioms.

[Diggory]

On Monday, 20 May 2013 at 06:53:34 UTC, Idan Arye wrote:
> On Monday, 20 May 2013 at 05:39:42 UTC, Diggory wrote:
>> In your logic you're assuming that the order of operations is 
>> maintained - without the correct memory barriers or 
>> synchronisation both the compiler and CPU are free to 
>> completely reorder any operations you do. That's why it's 
>> always a bug to access mutable shared data without 
>> synchronisation - any read not using some form of 
>> synchronisation could give you back any value that the memory 
>> is ever set to during the course of the program.
>
> It can't be THAT chaotic. Neither the compiler nor the CPU will 
> perform a check on a value and then go back in time to fetch an 
> old version of that value and return it. This kind of behavior 
> would break non-threaded code.

Of course it's possible, for example the code may produce the 
expected result if some invariant holds which does in fact hold 
if there was a single thread running, but with multiple threads 
the invariant is broken. Or more simply - the fact remains that 
you are writing on one thread (correctly using synchronisation) 
and reading from another (not using synchronisation) and 
synchronisation is required on both the read and the write. The 
compiler/CPU is then free to reorder the reads under the 
assumption that the value won't change, and this assumption is 
clearly wrong.

Basically most of your argument is just hoping that it will 
behave the way you want, but without having any real guarantees, 
and that's not the way to write thread-safe code, especially if 
it's going to be part of the standard library.