[patch] fix _OBJC_Module defined but not used warning

[Iain Sandoe]

Hi Aldy,

On 7 Jun 2015, at 12:37, Aldy Hernandez wrote:

> On 06/07/2015 06:19 AM, Andreas Schwab wrote:
>> Another fallout:
>> 
>> FAIL: obj-c++.dg/try-catch-5.mm -fgnu-runtime (test for excess errors)
>> Excess errors:
>> <built-in>: warning: '_OBJC_Module' defined but not used [-Wunused-variable]
> 
> check_global_declarations is called for more symbols now.  All the defined but not used errors I've seen in development have been legitimate.  For tests, the tests should be fixed.  For built-ins such as these, does the attached fix the problem?
> 
> It is up to the objc maintainers, we can either fix this with the attached patch,

The current patch is OK.

> or setting DECL_IN_SYSTEM_HEADER.

This seems a better long-term idea; however, I would prefer to go through all the cases where it would be applicable (including for the NeXT runtime) and apply that change as a coherent patch.  At the moment dealing with the NeXT stuff is a bit hampered by pr66448.

thanks,
Iain