Re: [Help-gsl] Re: Reg :: Error in declaring typedef of template class

[Sumit Adhikari]

Hello Akanksh,
  You are correct. but the base classes were written by myself and then I
wont be having any risk of memory leakage.
  By the way I cannot activate c++0x in my compiler :(, also I cannot
install the latest versions of g++ as my OS kernel is old :(
Regards,
Sumit

On Wed, Nov 11, 2009 at 2:59 PM, Akanksh Vashisth <address@hidden>wrote:

> Sorry about the earlier post, made a mistake there, only the base class
> non-virtual destructor shall be called, and the overhead will be the extra
> constructor of the derived class.
>
>
> 2009/11/11 Akanksh Vashisth <address@hidden>
>
>> Hello Sumit,
>>
>> I would advice against using this form:
>>
>> template<class T> class m_signal_out_if<T> : public m_signal_inout_if<T>
>> {};
>>
>> to do a pseudo-typedef, because here the assumption is that m_signal_inout_if
>> has a virtual destructor, because if m_signal_inout_if does not have a
>> virtual destructor, than the destruction of the base class shall not be
>> correct and might result in memory leaks if any of the base classes free up
>> allocated memory while destructing.
>>
>> So this technique works fine if the base class is known to not do any
>> allocations (and you are happy with undefined destruction behaviour) or if
>> it is known that the base class has a virtual destructor. Even so, the
>> overhead of the compiler generating the constructor and destructor of this
>> derived class is not acceptable or needed.
>>
>> And yes, C++0x will have support for templated typedefs.
>>
>> 2009/11/11 Sumit Adhikari <address@hidden>
>>
>>> Hello Akanksh,
>>> I already had a solution through which I could have wrote(in fact I used
>>> if you see mt other template classes) it as follows :
>>>    template<class T> class m_signal_out_if<T> : public
>>> m_signal_inout_if<T> {};
>>> But I was curious about this specific implementation of templated
>>> typedef. Well it is not supported. I do  know it is supported in c++0x.
>>> Thanks for the reply,
>>> Regards,
>>> Sumit
>>>
>>>
>>>
>>> On Wed, Nov 11, 2009 at 2:37 PM, Akanksh Vashisth <address@hidden>wrote:
>>>
>>>> Also, if a collection of such typedefs is needed, something like this
>>>> can be done ( but I would not suggest it as a default solution )
>>>>
>>>> template<typename T>
>>>> struct MyType
>>>> {
>>>>      typedef  m_signal_inout_if < T >  m_signal_out_if;
>>>>      typedef something_else_01<T> something_01;
>>>>      typedef something_else_02<T> something_02;
>>>> }
>>>>
>>>> and these can now be used as:
>>>>
>>>> MyType<SomeType1>:: m_signal_out_if variable_name_01;
>>>> MyType<SomeType2>:: something_01   variable_name_02;
>>>> MyType<SomeType3>:: something_02   variable_name_03;
>>>>
>>>> Hope this helps.
>>>>
>>>> Akanksh Vashisth
>>>> Graphics Engine Programmer
>>>> ArtVPS Ltd.
>>>> Cambridge, UK
>>>>
>>>> 2009/11/11 Akanksh Vashisth <address@hidden>
>>>>
>>>> Hello Sumit,
>>>>>
>>>>> In C++ typedef of a template is illegal, so the following code
>>>>>
>>>>>
>>>>> template < class T >
>>>>> typedef  m_signal_inout_if < T >  m_signal_out_if < T > ;
>>>>>
>>>>> will not compile.
>>>>>
>>>>> If you do want to typedef something like this, you need to surround it
>>>>> with a class definition, such as:
>>>>>
>>>>> template<typename T>
>>>>> struct m_signal_out_if
>>>>> {
>>>>>     typedef m_signal_inout_if  < T > type;
>>>>> }
>>>>>
>>>>> This can now be used as a type in the following way:
>>>>>
>>>>> m_signal_out_if<SomeType>::type variable_name;
>>>>>
>>>>> But seeing that the difference in you typedef name and the original
>>>>> class name is not a lot, the overhead and complexity of this typedef is 
>>>>> (in
>>>>> my opinion) not acceptable.
>>>>>
>>>>> Hope this helps.
>>>>>
>>>>> Akanksh Vashisth
>>>>> Graphics Engine Programmer
>>>>> ArtVPS Ltd.
>>>>> Cambridge, UK
>>>>>
>>>>> 2009/11/11 Sumit Adhikari <address@hidden>
>>>>>
>>>>> A little correction :
>>>>>>
>>>>>> # ifndef M_SIGNAL_OUT_IF_H_
>>>>>> # define M_SIGNAL_OUT_IF_H_
>>>>>>
>>>>>>
>>>>>> # include "m_signal_inout_if.h"
>>>>>>
>>>>>> template < class T > typedef  m_signal_inout_if < T >  m_signal_out_if
>>>>>> < T > ;
>>>>>>
>>>>>>
>>>>>>
>>>>>> # endif /*M_SIGNAL_OUT_IF_H_*/
>>>>>>
>>>>>>
>>>>>>
>>>>>> --------------------------------------------
>>>>>> Sumit Adhikari
>>>>>> System Design Engineer
>>>>>> austriamicrosystems AG
>>>>>> Business Unit : Automotive
>>>>>> Mob : 00-91-9885271710/00-91-9000161710
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 11/11/2009 8:49 AM, Sumit Adhikari wrote:
>>>>>>
>>>>>>> Hello All,
>>>>>>>
>>>>>>> I have a template class like as follows :
>>>>>>>
>>>>>>> # ifndef M_SIGNAL_INOUT_IF_H_
>>>>>>> # define M_SIGNAL_INOUT_IF_H_
>>>>>>>
>>>>>>> # include "m_signal_in_if.h"
>>>>>>>
>>>>>>> template < class T > class m_signal_inout_if : public m_signal_in_if
>>>>>>> < T > {
>>>>>>>   public :
>>>>>>>      virtual void write (const T&) = 0 ;
>>>>>>>      virtual void initialize(const T&) = 0;
>>>>>>> };
>>>>>>>
>>>>>>>
>>>>>>> # endif /*M_SIGNAL_INOUT_IF_H_*/
>>>>>>>
>>>>>>> I want to declare typedef of m_signal_inout_if and I have done it as
>>>>>>> follows :
>>>>>>>
>>>>>>> # ifndef M_SIGNAL_OUT_IF_H_
>>>>>>> # define M_SIGNAL_OUT_IF_H_
>>>>>>>
>>>>>>>
>>>>>>> # include "m_signal_inout_if.h"
>>>>>>>
>>>>>>> template < class T > m_signal_inout_if < T >  m_signal_out_if < T > ;
>>>>>>>
>>>>>>>
>>>>>>> # endif /*M_SIGNAL_OUT_IF_H_*/
>>>>>>>
>>>>>>>
>>>>>>> But I am getting syntax error in this process.
>>>>>>> Can anybody please tell me what is the wrong with it ?
>>>>>>> Regards,
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Help-gsl mailing list
>>>>>> address@hidden
>>>>>> http://lists.gnu.org/mailman/listinfo/help-gsl
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>>
>>> --------------------------------------------
>>> Sumit Adhikari
>>> System Design Engineer
>>> austriamicrosystems AG
>>> Business Unit : Automotive
>>> Mob : 00-91-9885271710/00-91-9000161710
>>>
>>
>>
>


-- 

--------------------------------------------
Sumit Adhikari
System Design Engineer
austriamicrosystems AG
Business Unit : Automotive
Mob : 00-91-9885271710/00-91-9000161710