Asp Forum - template related query

Soumen

10/10/2008 1:22:00 PM

I've a templatized class member function calling templatized member
function of another class.

//A.h
template <class T>
class A {
public:
static T* create();
};

//B.h
class B {

template<class T>
T* makeData();

};

template<class T>
T* B::makeData()
{
return A<T>::create();
}

I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
(Error is on the line where I include, not where I instantiate).

But I don't get compile error with gcc 4.2.2. Is there any way that I
can avoid this error in gcc3.3.6?

Regards,
~ Soumen

12 Answers

Soumen

10/10/2008 1:28:00 PM

On Oct 10, 6:22 pm, Soumen <soume...@gmail.com> wrote:
> I've a templatized class member function calling templatized member
> function of another class.
>
> //A.h
> template <class T>
> class A {
> public:
> static T* create();
>
> };
>
> //B.h
> class B {
> public:
> template<class T>
> T* makeData();
>
> };
>
> template<class T>
> T* B::makeData()
> {
> return A<T>::create();
>
> }
>
> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
> (Error is on the line where I include, not where I instantiate).
>
> But I don't get compile error with gcc 4.2.2. Is there any way that I
> can avoid this error in gcc3.3.6?
>
> Regards,
> ~ Soumen

Little correction A is not templatized class, rather create is
templatized method.

class A {
public:
template <class T>
static T* create();
};

Also, B::makeData() is like following:

//B.h
class B {
public:
template<class T>
T* makeData();

};

template<class T>
T* B::makeData()
{
return A::create<T>();
}

Hendrik Schober

10/10/2008 2:46:00 PM

Soumen wrote:
> [...]
> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
> (Error is on the line where I include, not where I instantiate).

So it must suspect you've done something wrong there.

> But I don't get compile error with gcc 4.2.2. Is there any way that I
> can avoid this error in gcc3.3.6?

Post the exact code that reproduces the error, tell us the
exact error message, and we can begin to speculate about the
compiler's reasoning and whether it's right or wrong.
Don't be as specific, and the answers probably won't get more
specific than mine from above.

> ~ Soumen

Schobi

Victor Bazarov

10/10/2008 3:02:00 PM

Hendrik Schober wrote:
> Soumen wrote:
>> [...]
>> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
>> (Error is on the line where I include, not where I instantiate).
>
> So it must suspect you've done something wrong there.

... or the compiler is incapable of processing the code because it is
malfunctioning due to a bug or to a misinterpretation of the Standard.
There is no way to tell for sure.

>
>> But I don't get compile error with gcc 4.2.2. Is there any way that I
>> can avoid this error in gcc3.3.6?
>
> Post the exact code that reproduces the error, tell us the
> exact error message, and we can begin to speculate about the
> compiler's reasoning and whether it's right or wrong.
> Don't be as specific, and the answers probably won't get more
> specific than mine from above.

Most likely the difference between versions is because the compiler
developers have caught up with the Standard or fixed some bugs in their
product. It would be wise to ask this question in the GCC forum [as
well as, not instead of, here].

>
>> ~ Soumen
>
> Schobi

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

Hendrik Schober

10/10/2008 5:54:00 PM

Victor Bazarov wrote:
> Hendrik Schober wrote:
>> Soumen wrote:
>>> [...]
>>> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
>>> (Error is on the line where I include, not where I instantiate).
>> So it must suspect you've done something wrong there.
>
> ... or the compiler is incapable of processing the code because it is
> malfunctioning due to a bug or to a misinterpretation of the Standard.

What would be the difference?

> [...]
> V

Schobi

Kai-Uwe Bux

10/10/2008 11:20:00 PM

Hendrik Schober wrote:

> Victor Bazarov wrote:
>> Hendrik Schober wrote:
>>> Soumen wrote:
>>>> [...]
>>>> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
>>>> (Error is on the line where I include, not where I instantiate).
>>> So it must suspect you've done something wrong there.
>>
>> ... or the compiler is incapable of processing the code because it is
>> malfunctioning due to a bug or to a misinterpretation of the Standard.
>
> What would be the difference?

The difference, as I understand it, is _who_ had done something wrong: the
programmer of the code or the programmer of the compiler.

Best

Kai-Uwe Bux

Hendrik Schober

10/11/2008 11:43:00 PM

Kai-Uwe Bux wrote:
> Hendrik Schober wrote:
>
>> Victor Bazarov wrote:
>>> Hendrik Schober wrote:
>>>> Soumen wrote:
>>>>> [...]
>>>>> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
>>>>> (Error is on the line where I include, not where I instantiate).
>>>> So it must suspect you've done something wrong there.
>>> ... or the compiler is incapable of processing the code because it is
>>> malfunctioning due to a bug or to a misinterpretation of the Standard.
>> What would be the difference?
>
> The difference, as I understand it, is _who_ had done something wrong: the
> programmer of the code or the programmer of the compiler.

If I say the compiler /suspects/ the programmer has done
something wrong, then who's accused? :)

> Kai-Uwe Bux

Schobi

Kai-Uwe Bux

10/14/2008 2:11:00 PM

Hendrik Schober wrote:

> Kai-Uwe Bux wrote:
>> Hendrik Schober wrote:
>>
>>> Victor Bazarov wrote:
>>>> Hendrik Schober wrote:
>>>>> Soumen wrote:
>>>>>> [...]
>>>>>> I get a compile error (gcc 3.3.6) when I include B.h in some X.cpp.
>>>>>> (Error is on the line where I include, not where I instantiate).
>>>>> So it must suspect you've done something wrong there.
>>>> ... or the compiler is incapable of processing the code because it is
>>>> malfunctioning due to a bug or to a misinterpretation of the Standard.
>>> What would be the difference?
>>
>> The difference, as I understand it, is _who_ had done something wrong:
>> the programmer of the code or the programmer of the compiler.
>
> If I say the compiler /suspects/ the programmer has done
> something wrong, then who's accused? :)

The programmer and not the compiler. In the vast majority of cases, the
compilers suspicions are right. I get compiler errors almost all the time,
but I have found only 10 compiler bugs so far.

Best

Kai-Uwe Bux

Hendrik Schober

10/15/2008 11:47:00 AM

Kai-Uwe Bux wrote:
> [...] I get compiler errors almost all the time,
> but I have found only 10 compiler bugs so far.

You need to do more porting. Or more template stuff. Or both. :)

> Kai-Uwe Bux

Schobi

James Kanze

10/15/2008 7:21:00 PM

On Oct 15, 1:46 pm, Hendrik Schober <spamt...@gmx.de> wrote:
> Kai-Uwe Bux wrote:
> > [...] I get compiler errors almost all the time,
> > but I have found only 10 compiler bugs so far.

> You need to do more porting. Or more template stuff. Or both. :)

It depends on what his boss is paying him to do: write working
(and maintainable) code, or stress test compilers. With modern
compilers, it's actually fairly rare to stumble on a compiler
bug unless you're pushing the envelope well beyond what is
reasonable in a normal production environment.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34

Hendrik Schober

10/18/2008 7:48:00 PM

James Kanze wrote:
> On Oct 15, 1:46 pm, Hendrik Schober <spamt...@gmx.de> wrote:
>> Kai-Uwe Bux wrote:
>>> [...] I get compiler errors almost all the time,
>>> but I have found only 10 compiler bugs so far.
>
>> You need to do more porting. Or more template stuff. Or both. :)
>
> It depends on what his boss is paying him to do: write working
> (and maintainable) code, or stress test compilers. With modern
> compilers, it's actually fairly rare to stumble on a compiler
> bug unless you're pushing the envelope well beyond what is
> reasonable in a normal production environment.

In the last decade I have written code that needed to compile
using several versions of Borland, Microsoft, Metrowerks, GCC,
multiplied with several std lib implementations (and versions
thereof) and, at least with GCC, several platforms. Although,
in my experience, too, most of the time when at first I thought
I'd found a compiler error I have found one of my own, I did
find several dozen of compiler errors in that time -- and not
just in obscure corner cases. And quite a lot of my 10 years
old code is still in use (although it doesn't need all that
much maintenance nowadays).
But, yes, I was paid to write portable code (and to get compiler
vendors to send us hotfixes).

Schobi

comp.lang.c++

template related query

Soumen

Soumen

Hendrik Schober

Victor Bazarov

Hendrik Schober

Kai-Uwe Bux

Hendrik Schober

Kai-Uwe Bux

Hendrik Schober

James Kanze

Hendrik Schober

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