Re: What does zero-length array mean at file scope?

[Dave Korn <dave dot korn dot cygwin at googlemail dot com>]

Dave Korn wrote:
> Dave Korn wrote:
>> I've read http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html about six
>> times and can't see anywhere it even hints that you can use this syntax
>> anywhere except as the trailing member of a struct.
> 
> Andrew Haley wrote:
>> But zero-length arrays are a gcc extension.  There's nothing that limits
>> them to the last member of a struct.  zero-length arrays must be rejected
>> with -pedantic, but not otherwise.
> 
>> Because it's a documented gcc extension.
> 
>   Obviously I can't see for looking; can you please point me to the precise
> chapter/page/paragraph/line that I should have found earlier?

  (I honestly mean that, no sarcasm intended; it was late at night and I was
tired, I could easily have misread or overlooked something.)  I did find this
comment in varasm.c:assemble_noswitch_variable() that says we need to handle
this case:

  /* Don't allocate zero bytes of common,
     since that means "undefined external" in the linker.  */
  if (size == 0)
    rounded = 1;

... so I guess it counts as a backend bug if the backend still emits a zero in
the .comm directive, and that the documentation of ASM_OUTPUT.*COMMON should
probably be improved to warn of the danger that size may be zero.

    cheers,
      DaveK