Re: what is this [0 ... n] array notation?

[Troy Hanson <thanson@xxxxxxxx>]

Robert P. J. Day wrote:

On Tue, 16 Jan 2007, Mike Frysinger wrote:

  

On 1/16/07, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
    

drivers/scsi/ipr.c:
        const u8 zero_sn[IPR_SERIAL_NUM_LEN] = { [0 ...
IPR_SERIAL_NUM_LEN-1] = '0' };

where does this "..." range syntax come from?  i know gcc supports the
*case* range extension, but i don't know where the above *arrray*
range syntax comes from.
      

just like it looks ... instead of writing '0' IPR_SERIAL_NUM_LEN
times, gcc will fill it for you
    

sorry, i wasn't clear.  i wanted to know where that syntax is
*defined*.  i don't see it in my C99 spec, and it's not listed as a
gcc extension.  so where did it come from?

rday
  

The range initialization syntax is a GNU extension.

>From http://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html:

To initialize a range of elements to the same value, write `[first ... last] = value'. This is a GNU extension. For example,

     int widths[] = { [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 };

If the value in it has side-effects, the side-effects will happen only once, not for each initialized field by the range initializer.

Note that the length of the array is the highest value specified plus one.