Re: -Wweak-vtables warnings (was: Bison 3.2.91 released [beta])

[Derek Clegg]

Hi, Akim —

On Jan 19, 2019, at 11:49 PM, Akim Demaille <address@hidden> wrote:
> 
> Hi Derek!
> 
>> Le 19 janv. 2019 à 20:47, Derek Clegg <address@hidden> a écrit :
>> 
>> I ran into just one issue:
>> 
>> aux/parser-internal.h:429:12: error: 'syntax_error' has no out-of-line 
>> virtual
>>     method definitions; its vtable will be emitted in every translation unit
>>     [-Werror,-Wweak-vtables]
>>   struct syntax_error : std::runtime_error
>>          ^
>> 1 error generated.
> 
> I don't think I will address this warning, the cure is way worse than the 
> problem.
> 
> To add the destructor, I must make the signature explicit, and it cannot be 
> different from the one in the base class, so I must add noexcept:
> 
>   ~syntax_error () YY_NOEXCEPT;

In C++98 the signature is
  virtual ~exception() throw();
and in C++11 the signature is
  virtual ~exception();
so this only has to be handled specially for C++98.

Wouldn’t it be sufficient to explicitly write

#if 201103L <= YY_CPLUSPLUS
  ~syntax_error();
#else
  ~syntax_error() throw();
#endif

and similarly for the definition?

It seems problematic to redefine YY_NOEXCEPT, especially since “noexcept” and 
“throw()” aren’t used equivalently.

Derek