Re: [Boost-users] boost::exception_detail::error_info_base does not have virtual destructor

Subject: Re: [Boost-users] boost::exception_detail::error_info_base does not have virtual destructor
From: Kenny Riddile (kfriddile_at_[hidden])
Date: 2011-03-17 14:27:51

On 3/17/2011 2:17 PM, Ted Byers wrote:
> Hi Stevem,
>
>> -----Original Message-----
>> From: boost-users-bounces_at_[hidden]
> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Steven Watanabe
>> Sent: March-17-11 12:37 PM
>> To: boost-users_at_[hidden]
>> Subject: Re: [Boost-users] boost::exception_detail::error_info_base does
> not have virtual destructor
>>
>> AMDG
>>
>> On 03/17/2011 08:50 AM, Jens Auer wrote:
>>> I am compiling a project with a more strict warning set and got the
> following reports:
>>> Error	29	error C4265:
> 'boost::exception_detail::error_info_base' : class has virtual functions,
> but destructor is not virtual
> c:\work\svn\sandbox\externals\boost\include\boost-1_45\boost\exception\detai
> l\error_info_impl.hpp	36
>>>
>>> Error	30	error C4265: 'boost::error_info<Tag,T>' : class has
> virtual functions, but destructor is not virtual
> c:\work\svn\sandbox\externals\boost\include\boost-1_45\boost\exception\detai
> l\error_info_impl.hpp	69
>>>
>>> IMHO these classes should have a virtual destructor as they are intended
> to be used as base classes.
>>
>> No they shouldn't. A virtual destructor
>> is only needed when deleting through
>> a base class pointer. This is explicitly forbidden by making the destructor
> protected.
>
> I must respectfully disagree.
>
> There are two ways to look at this 'should'.  First, there is what is
> required or permitted by the standard.  Second, there is what is useful in
> managing a  software development project.  When I am trying to help my
> juniors develop good programming habits, one of the things I want them to do
> is always provide a virtual destructor whenever they make one or more member
> functions virtual.  That lets a team comprised of many more junior
> programmers than really really old guys like me avoid a lot of subtle bugs.
> And I don't see a significant down side to making a destructor virtual.
> Hence, when I am mentoring junior programmers, I routinely advise them to
> make destructors virtual whenever they need one of the other member
> functions to be virtual, whenever the issue arises.
>
> Are you aware of a significant downside to making destructors virtual as a
> matter of habit?
>
> Cheers
>
> Ted

Why not just encourage the habit of making *public* destructors virtual 
in the presence of one or more other virtual methods?  That is, after 
all, when a virtual destructor can be necessary.