[c-common.c] warnings: -Wformat and -Wnonnull

[Paolo Bonzini]

DJ Delorie wrote:
>>| Not sure what to do about this one though:
>>| 
>>|   if (warn_format || warn_missing_format_attribute)
>>|       check_function_format (attrs, params);
>>
>>could we leave it as is?  Or do you see some potential confusion?
> 
> I meant, which OPT_* to pass to warning() for the warnings within
> check_function_format().

There are further if's within the function.

The sole call to warning() is already guarded by OPT_Wattributes which 
is wrong and should be changed to OPT_Wmissing_format_attribute. 
check_format_info, instead, is called by check_function_format and 
warnings there should be guarded by OPT_Wformat.

HTH,

Paolo