[Bug c++/18306] New: seems not possible to specialize a template member function

[Bug c++/18306] New: seems not possible to specialize a template member function

[ramya dot chandar at wipro dot com]

Environment     : i686-pc-linux-gnu
Compiler Version: GCC 3.3.2 
Kernel Version  : 2.4.7-10

It seems, not possible to specialize a template member functions const. I got a
file(.impl) which got the following template functions( generalized and
specialized template functions ) and i got the corresponding header file ( where
this .impl file is getting included ).

IOCM::Status IOCM_SequenceTempl<IOCM::Char>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<IOCM::Octet>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<IOCM::Short>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<IOCM::UShort>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<IOCM::Long>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<IOCM::ULong>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<IOCM::Float>::_skip(IOCM::MessageBox& msgBox);
IOCM::Status IOCM_SequenceTempl<T>::_skip(IOCM::MessageBox& msgBox);


But, the build is getting failed, with the following error( for all the template
functions ).

/cm4/objects/gant-c/ghostr/cm4/fsn/app/asam/eqptDomain/eqptMgntCore/common/AppliqueSensorListener.o(.text+0x0):
In function `IOCM_SequenceTempl<char>::_size() const':
/cm4/fsn/include/iocm/Sequence.impl:293: multiple definition of
`IOCM_SequenceTempl<char>::_size() const'
/cm4/objects/gant-c/ghostr/cm4/fsn/app/asam/eqptDomain/eqptMgntCore/common/AppliqueHandler.o(.text+0x0):/cm4/fsn/include/iocm/Sequence.impl:293:
first defined here
/cm4/objects/gant-c/ghostr/cm4/fsn/app/asam/eqptDomain/eqptMgntCore/common/AppliqueSensorListener.o(.text+0x18):
In function `IOCM_SequenceTempl<char>::_pack(IOCM_MessageBox&) const':
/cm4/fsn/include/iocm/Sequence.impl:305: multiple definition of
`IOCM_SequenceTempl<char>::_pack(IOCM_MessageBox&) const'
/cm4/objects/gant-c/ghostr/cm4/fsn/app/asam/eqptDomain/eqptMgntCore/common/AppliqueHandler.o(.text+0x18):/cm4/fsn/include/iocm/Sequence.impl:305:
first defined here

There is no problem with 2.95.3

But, when i remove the .impl file( which got the template function definitions )
from the corresponding header file, compilation went through, but its failing
during linking stage for the same reason giving the following error message for
all the template functions.

Linking fails with the following error( for all the template functions ).

/cm4/fsn/app/asam/atm2/nt/../export/idl/AtmApplication_ifc.cc:344: undefined
reference to `IOCM_SequenceTempl<Eqpt::LogicalIfIndex>::_size(void) const'
/cm4/fsn/app/asam/atm2/nt/../export/idl/AtmApplication_ifc.cc:349: undefined
reference to `IOCM_SequenceTempl<Eqpt::LogicalIfIndex>::_pack(IOCM_MessageBox &)
const'

-- 
           Summary: seems not possible to specialize a template member
                    function
           Product: gcc
           Version: 3.2.2
            Status: UNCONFIRMED
          Severity: critical
          Priority: P1
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ramya dot chandar at wipro dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[ramya dot chandar at wipro dot com]

------- Additional Comments From ramya dot chandar at wipro dot com  2004-11-05 04:19 -------
Created an attachment (id=7476)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7476&action=view)
preprocessed source for AppliqueHandler.cc


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[ramya dot chandar at wipro dot com]

------- Additional Comments From ramya dot chandar at wipro dot com  2004-11-05 04:21 -------
Created an attachment (id=7477)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7477&action=view)
preprocessed code for AppliqueSensorListener.cc


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-05 04:28 -------
As I said before the code you have here is invalid C++.

you have to add
template<> in front of each of the specialization of a template member function.

Also you have problems with template namelookup also (read the 3.4 release notes for the problems 
which I am talking about).

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-05 05:03 -------
Invalid, as what you are doing is called explicit specializtion and when this happens you instantiate the 
template and now you are violating the one defintional rule (which is 14.7/5 in the C++ standard).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-11-05 19:27 -------
These are all duplicates of PR 15552 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-11-05 19:29 -------
Duplicate of PR 15552. 

*** This bug has been marked as a duplicate of 15552 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[ramya dot chandar at wipro dot com]

------- Additional Comments From ramya dot chandar at wipro dot com  2004-11-23 12:31 -------
Subject: Re:  seems not possible to specialize a template member
 function

clarification please...

I tried including "template<>" in front of each of the specialized template member functions. It doesn't solve the problem.

Looking at my code, for my knowledge, it doesn't look like violating the rule (14.7/5). Can you please tell me what exacting is going wrong and how does it violates the rule. 

According to 14.7/5 rule, 
A  non-exported template that is neither explicitly specialized nor explicitly instan-
  tiated must be defined in  every  translation  unit  in  which  it  is implicitly   instantiated or  explicitly  instantiated; no diagnostic is required. An  exported  template need  only  be declared (and not necessarily defined) in a translation unit in which it is instantiated.  A template function  declared  both exported and inline is just inline and not exported.

But, in the code i have attached,( since the generalised and specialized template member functions ) are explicitely instantiated in a module( Sequence.impl ), its not defined separately in any of the translation unit. Still why does it fail.

I don't know how is it violating the rule. Can you please tell me, what needs to be done exactly.

Thanks,
Ramya.

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-05 04:28 -------
As I said before the code you have here is invalid C++.

you have to add
template<> in front of each of the specialization of a template member function.

Also you have problems with template namelookup also (read the 3.4 release notes for the problems 
which I am talking about).

-- 

pinskia at gcc dot gnu dot org wrote:

>------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-05 05:03 -------
>Invalid, as what you are doing is called explicit specializtion and when this happens you instantiate the 
>template and now you are violating the one defintional rule (which is 14.7/5 in the C++ standard).
>
>  
>




-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[ramya dot chandar at wipro dot com]

------- Additional Comments From ramya dot chandar at wipro dot com  2004-11-24 06:55 -------
clarification please...

I tried including "template<>" in front of each of the specialized template
member functions. It doesn't solve the problem.

But, in the code i have attached,( since the generalised and specialized
template member functions ) are explicitely instantiated in a module(
Sequence.impl ), its not defined separately in any of the translation unit.
Still why does it fail.

I don't know how is it violating the rule. Can you please tell me, what needs to
be done exactly.



-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|DUPLICATE                   |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-24 19:11 -------
Invalid, as what you are doing is called explicit specializtion and when this happens you instantiate the 
template and now you are violating the one defintional rule (which is 14.7/5 in the C++ standard).

Note that if you use 3.4.0, it works with adding template<>.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306

[Bug c++/18306] seems not possible to specialize a template member function

[ramya dot chandar at wipro dot com]

------- Additional Comments From ramya dot chandar at wipro dot com  2005-03-08 09:44 -------
(In reply to comment #9)
> Invalid, as what you are doing is called explicit specializtion and when this
happens you instantiate the 
> template and now you are violating the one defintional rule (which is 14.7/5
in the C++ standard).
> 
> Note that if you use 3.4.0, it works with adding template<>.

(In reply to comment #9)
> Invalid, as what you are doing is called explicit specializtion and when this
happens you instantiate the 
> template and now you are violating the one defintional rule (which is 14.7/5
in the C++ standard).
> 
> Note that if you use 3.4.0, it works with adding template<>.


Since solving this Compiler error is very critical to us, We made  some more
investigation in our code to see if it violates the one defintional rule of C++.

Here is our consolidated investigation.

Explicit template specialization itself does NOT instantiate the template. It
only specializes it. Hence, we feel, it is not violating any C++ standard rules.

E.g.,

template<class T> class A {
    public:
        void f(T t) { /* ... */ } // definition in general case
};

template<> void A<int>::f(int i) { /* ... */ } // definition in specific, i.e.,
'T=int' case

The above code does NOT instantiate the template, it only does explicit
specialization of its 'f' member function for the case of  'T= int'.

Template instantiation is an another issue, and it can happen either implicitly
or explicitly.
Implicit template instantiation happens when the template is being used in the
way that its usage requires the instantiation.
E.g.,

A<int>* aP; // No instantiation happens!
A<int>  a;  // Implicit template instantiation happens!

Explicit template instantiation happens when the explicit template instantiation
syntax is applied.
E.g.,

template class A<int>;
template void A<int>::f(int);
template class A<char>;

Looking at our IOCM Sequence.hh and Sequence.impl  files, within these files the
templates, that generate errors with the new GNU compiler( 3.3.2), are surely
NOT instantiated.

However it is true that the template specializations in the Sequence.impl files
should have template<> prefix (but most of the compilers are actually accept
them without this as well).

I checked these files with the Microsoft Visual Studio .Net 2003 which is
commonly known as having one of the compilers that most follow the C++ standard.
With this compiler everything compiles well (in fact, with or without the
template<> prefix).

Can you please explain us,  if it is the problem with  GCC 3.3.2 compiler.
surprisingly, with  GCC 2.95.3 compiler, we are able to compile the same code
without any changes.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18306