gcc 4 can not resolve member var derived from base class in atemplate class

[steve yee]

#include <iostream>
#include <list>

template<class mt_policy>
class Base
{
public:
int a;
};

template<class mt_policy = int>
class signal0 : public Base<mt_policy>
{
public:
void aaa()
{
std::cout<<"a = "<<a<<std::endl ;
}
};

int main()
{
signal0<intp;
p.aaa();
}
~

test.cpp: In member function ‘void signal0<mt_poli cy>::aaa()’:
test.cpp:17: error: ‘a’ was not declared in this scope

[acehreli@gmail.com]

Re: gcc 4 can not resolve member var derived from base class in atemplate class

On Jul 1, 9:05 am, steve yee <yiton...@gmail .comwrote:

#include <iostream>
#include <list>
>
template<class mt_policy>
class Base
{
public:
int a;
>
};
>
template<class mt_policy = int>
class signal0 : public Base<mt_policy>
{
public:
void aaa()
{
std::cout<<"a = "<<a<<std::endl ;

This is the definition of class template signal0, not an instantiation
of it. So the compiler cannot know whether any Base<mt_policyw ill
provide an 'a'. For example, some specialization may not have an a.

The compiler cannot assume that a missing name will be available
through a templated base. What if there were two bases?

The solution is to fully qualify 'a': Base<mt_policy> ::a

}
>
};
>
int main()
{
signal0<intp;
p.aaa();}
>
~
>
test.cpp: In member function ‘void signal0<mt_poli cy>::aaa()’:
test.cpp:17: error: ‘a’ was not declared in this scope

Ali

[Juha Nieminen]

Re: gcc 4 can not resolve member var derived from base class in atemplate class

steve yee wrote:

test.cpp: In member function ‘void signal0<mt_poli cy>::aaa()’:
test.cpp:17: error: ‘a’ was not declared in this scope

You have to add this to your signal0 class:

using Base<mt_policy> ::a;

I don't remember now why this was standardized like that.

[steve yee]

Re: gcc 4 can not resolve member var derived from base class in atemplate class


so this is a standard, not a bug of gcc? but vc9 can compile it.


On Jul 2, 2:00 am, Juha Nieminen <nos...@thanks. invalidwrote:

steve yee wrote:

test.cpp: In member function ‘void signal0<mt_poli cy>::aaa()’:
test.cpp:17: error: ‘a’ was not declared in this scope

>
  You have to add this to your signal0 class:
>
using Base<mt_policy> ::a;
>
  I don't remember now why this was standardized like that.

[Juha Nieminen]

Re: gcc 4 can not resolve member var derived from base class in atemplate class

steve yee wrote:

so this is a standard, not a bug of gcc? but vc9 can compile it.

VC9 doesn't obey the standard in all respects.

[Kyle]

Re: gcc 4 can not resolve member var derived from base class in atemplate class

steve yee wrote:

#include<iostre am>
#include<list>
>
template<class mt_policy>
class Base
{
public:
int a;
};
>
template<class mt_policy = int>
class signal0 : public Base<mt_policy>
{
public:
void aaa()
{
std::cout<<"a ="<<a<<std::end l;

here you need to make name 'a' dependent on template parameter
one of ways to do this, is to access 'a' through this pointer:

std::cout<<"a ="<<this->a<<std::endl ;

}
};
>
int main()
{
signal0<int p;
p.aaa();
}
~
>
test.cpp: In member function ‘void signal0<mt_poli cy>::aaa()’:
test.cpp:17: error: ‘a’ was not declared in this scope

[Bo Persson]

Re: gcc 4 can not resolve member var derived from base class in a template class

Juha Nieminen wrote:

steve yee wrote:

>so this is a standard, not a bug of gcc? but vc9 can compile it.

>
VC9 doesn't obey the standard in all respects.

It does respect this, if you ask it too (option /Za). Default is to
compile old, pre-standard, Windows code.


Bo Persson