extern const initialized warns in C

[Georg-Johann Lay]

On 22.01.2018 16:20, Jonathan Wakely wrote:
> On 21 January 2018 at 12:08, Georg-Johann Lay wrote:
>> Jay K schrieb:
>>>
>>> extern const int foo = 123;
>>>
>>> Why does this warn?
>>> This is a valid portable form, with the same meaning
>>> across all compilers, and, importantly, portably
>>> to C and C++.
>>
>> I also wondered about this.
>>
>> In C99 §6.9.2 "External object definitions" there's actually
>> the following example in clause 4:
>>
>> extern int i3 = 3; // definition, external linkage
> 
> That's a different case. There's no advantage to the 'extern' here,
> because the code means the same thing in C and C++ without the
> 'extern', so just leave it out.

I'd rather like to know why GCC is throwing a warning here.

It's clear how to hack the C source, but that's a different point.

It's just the case that I don't see any problem with that construct,
and it was worth an explicit example in the standard.  Or is it
common practice to warn constructs that are "no advantage"?

Johann