[cfe-dev] Question about arrays in blocks

[Adler, Arik]

Does Clang supposed to disallow such feature for the sake of efficiency?
Isn't a warning message will be more suitable in this case?


From: jahanian [mailto:fjahanian at apple.com]
Sent: Wednesday, June 19, 2013 21:32
To: Adler, Arik
Cc: cfe-dev at cs.uiuc.edu
Subject: Re: [cfe-dev] Question about arrays in blocks

It is an efficiency issue. It requires copying entire array into the block descriptor.
- Fariborz

On Jun 19, 2013, at 2:53 AM, "Adler, Arik" <arik.adler at intel.com<mailto:arik.adler at intel.com>> wrote:



I am now testing blocks usage in OpenCL.
I noticed that Clang forbids using an arrays within blocks (Clang forbid array capturing)

For Example, the following code will fail to compile because there is a reference to an array within a block.
But if the line referring to block will comment out and the line with reference to integer pointer ('j') will comment in, the code will pass.

void block_arr()
{
  int res = 0;
  int i[4] = { 3, 4, 4, 1 };
  int* j = i;

  int (^test_block )(int) = ^(int num)
    {
      return num + i[1];      // This is an error: "error: cannot refer to declaration with an array type inside block"
//      return num + j[1];    // This would work
    };

    res = test_block(7);
}


Do you know what is the reason behind this limitation?
And why it is possible to use a regular pointers but arrays are forbidden?

Thanks,
Arik

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