Subj : Re: Adding thread support for C...
To   : comp.programming.threads
From : Ian
Date : Sat Jul 23 2005 12:11 pm

Joe Seigh wrote:
>> The compiler was eliminating the wait-loops [as it should]. We had to 
>> introduce a mechanism to inhibit this optimization.
>>
>> It turns out that, as the compiler starts optimizing more, and worse, 
>> doing whole program optimizations, it becomes critical with 
>> multi-threaded programs to make sure that the compiler can distinguish 
>> between optimizations that would be correct in single-threaded C but 
>> are invalid in multi-threaded codes.
>>
> 
> What you won't get is support for writing your own synchronization api's,
> Not unless you can construct them out of the synchronization functions they
> give you.  Probablly something like the atomic stuff in JSR 166.  You
> might want to take a look at that.
> 
> Also look at the current discussion of what's being looked at for C++.
> http://decadentplace.org.uk/pipermail/cpp-threads_decadentplace.org.uk/
> 
> What people don't realize is that most C compilers can't do all the 
> optimization
> they could do because they'd break all kinds of things,  Linux kernel 
> and lot's
> of device drivers for instance.  Once you put in official thread support 
> you can
> be rigidly restricted to the rules.  No more coding outside the box.
> 
I've seen a couple of embedded compilers that provide extensions to work 
round these issues, maybe a better solution is through pragmas or 
compiler options as this stuff tends to be platform specific.

Ian

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