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:
> 
>>   ELF GAS/LD seem happy enough when presented with a ".comm foo,0" directive,
>> but PE does rather literally what you asked, and gives you no data object,
>> leading to i0 in the above being an undefined reference at link time.
> 
>   After a bit further digging, it turns out that this is because PE uses the
> same representation for an external symbol as would represent a common of size
> 0, so if you define such a common, it magically becomes an undefined external
> symbol instead!

  And testing it on Linux, I see that the linker goes ahead and assigns zero
bytes of the common area to i0, then assigns four bytes of common space to i1
at the same address, so writing to i0[0] aliases and alters i1.  That
certainly sounds like undefined behaviour to me!

    cheers,
      DaveK