[cfe-dev] Question about arrays in blocks

[Adler, Arik]

Another alternative is to copy the pointer and not the whole array (as it done in C)


From: Eli Friedman [mailto:eli.friedman at gmail.com]
Sent: Wednesday, June 19, 2013 20:46
To: Adler, Arik
Cc: cfe-dev at cs.uiuc.edu
Subject: Re: [cfe-dev] Question about arrays in blocks

On Wed, 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?


IIRC, it's just so that people don't accidentally make implicit copies of large arrays.

-Eli
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