Jonathon,
This is being tracked by our internal bug number 8590846. I'm told that the
workaround is to place the array within a structure:
__block struct {
double result[COUNT];
} results;
davez
On Dec 14, 2010, at 7:30 PM, Jonathon Kuo wrote:
> I'm trying to learn GCD and reading
> http://developer.apple.com/library/mac/#featuredarticles/BlocksGCD/index.html
> But the Global Concurrent Queues example in that document (last updated
> 2010-11-10) doesn't even compile. It complains about accessing array 'result'
> from within the block:
>
> #define COUNT 128
> __block double result[COUNT];
> dispatch_apply(COUNT, q_default, ^(size_t i){
> result[i] = complex_calculation(i); /* <=== ERROR HERE!
> });
> double sum = 0;
> for (int i=0; i < COUNT; i++) sum += result[i];
>
>
> What is wrong here? This looks like it should work. Below is my full program.
> -Jonathon
>
>
> #include <dispatch/dispatch.h>
> #include <stdio.h>
> #define COUNT 128
>
> double complex_calculation( int i )
> {
> return i * 3.14;
> }
>
> int main()
> {
> int i = 0;
> __block double result[COUNT];
>
> dispatch_queue_t q_default;
> /* get default queue */
> q_default = dispatch_get_global_queue(0, 0);
>
> dispatch_apply(COUNT, q_default, ^(size_t i) {
> result[i] = complex_calculation(i); /* <=== ERROR HERE!
> });
>
> double sum = 0;
> for (i=0; i < COUNT; i++) sum += result[i];
> printf("%f\n", sum);
> return 0;
> }
>
> $ cc -g blk3.c -o blk3
> blk3.c: In function ‘__main_block_invoke_1’:
> blk3.c:20: error: cannot access __block variable of array type inside block
>
>
> _______________________________________________
>
> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
>
> Please do not post admin requests or moderator comments to the list.
> Contact the moderators at cocoa-dev-admins(at)lists.apple.com
>
> Help/Unsubscribe/Update your Subscription:
> http://lists.apple.com/mailman/options/cocoa-dev/zarzycki%40apple.com
>
> This email sent to zarzy...@apple.com
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
