On Fri, Sep 4, 2009 at 12:11 AM, Bakul Shah
<bakul+pl...@bitblocks.com<bakul%2bpl...@bitblocks.com>
> wrote:
> On Thu, 03 Sep 2009 22:35:35 PDT David Leimbach <leim...@gmail.com>
> wrote:
> >
> >
> > Actually, reading on a bit more they deal with the "variable capture"
> > talking about const copies.
> >
> > Automatic storage variables not marked with __block are imported as
> > const copies.
> >
> > The simplest example is that of importing a variable of type int.
> >
> > int x = 10;
> > void (^vv)(void) = ^{ printf("x is %d\n", x); }
> > x = 11;
> > vv();
> >
> > would be compiled
> >
> > struct __block_literal_2 {
> > void *isa;
> > int flags;
> > int reserved;
> > void (*invoke)(struct __block_literal_2 *);
> > struct __block_descriptor_2 *descriptor;
> > const int x;
> > };
> >
> > void __block_invoke_2(struct __block_literal_2 *_block) {
> > printf("x is %d\n", _block->x);
> > }
> >
> > static struct __block_descriptor_2 {
> > unsigned long int reserved;
> > unsigned long int Block_size;
> > } __block_descriptor_2 = { 0, sizeof(struct __block_literal_2) };
> >
> > and
> >
> > struct __block_literal_2 __block_literal_2 = {
> > &_NSConcreteStackBlock,
> > (1<<29), <uninitialized>,
> > __block_invoke_2,
> > &__block_descriptor_2,
> > x
> > };
> >
> > In summary, scalars, structures, unions, and function pointers are
> > generally imported as const copies with no need for helper functions.
>
> Just read this after posting my last message.
>
> But this has no more to do with parallelism than any other
> feature of C. If you used __block vars in a block, you'd
> still need to lock them when the block is called from
> different threads.
>
>
I just wrote a prime sieve with terrible shutdown synchronization you can
look at here:
http://paste.lisp.org/display/86549
Dave
