deriving template classes: gcc 3.4 complains

deriving template classes: gcc 3.4 complains

[Joachim Schoeberl]

The piece of C++ code below compiles with gcc 3.3,
but gcc version 3.4 20030924 (experimental) complains:

test34.cpp: In constructor `derived<A>::derived(int)':
test34.cpp:14: error: `i' undeclared (first use this function)
test34.cpp:14: error: (Each undeclared identifier is reported only once 
for each function it appears in.)

Is there something wrong with my code ?

thanks, Joachim



template <typename A>
class base
{
public:
  int i;
};

template <typename A>
class derived : public base<A>
{
public:
  derived (int ai)
    { i = ai; }
};

int main ()
{
  derived<int> i(5);
  return 0;
}

Re: deriving template classes: gcc 3.4 complains

[Gerald Pfeifer]

On Wed, 1 Oct 2003, Joachim Schoeberl wrote:
> test34.cpp: In constructor `derived<A>::derived(int)':
> test34.cpp:14: error: `i' undeclared (first use this function)
> test34.cpp:14: error: (Each undeclared identifier is reported only once
> for each function it appears in.)
>
> Is there something wrong with my code ?

I believe the third item under C++ at

  http://gcc.gnu.org/gcc-3.4/changes.html

might be relevant here.

Gerald
-- 
Gerald Pfeifer (Jerry)   gerald@pfeifer.com   http://www.pfeifer.com/gerald/

Re: deriving template classes: gcc 3.4 complains

[George Garvey]

On Wed, Oct 01, 2003 at 08:51:58PM +0200, Gerald Pfeifer wrote:
>   http://gcc.gnu.org/gcc-3.4/changes.html

Quoting from the above document, is this a typo:

The cast-as-lvalue extension has been removed. In particular, code like this: 

        int i;
        (char)a = 5;
        

is no longer accepted.

Re: deriving template classes: gcc 3.4 complains

[Andrew Pinski]

On Oct 1, 2003, at 19:48, George Garvey wrote:

> On Wed, Oct 01, 2003 at 08:51:58PM +0200, Gerald Pfeifer wrote:
>>   http://gcc.gnu.org/gcc-3.4/changes.html
>
> Quoting from the above document, is this a typo:
>
> The cast-as-lvalue extension has been removed. In particular, code 
> like this:
>
>         int i;
>         (char)a = 5;
>
>
> is no longer accepted.
>

No it is not, the extension causes too many problems than the benefits 
you get from it.
Any way why do you think it is a typo?

Thanks,
Andrew Pinski

Re: deriving template classes: gcc 3.4 complains

[George Garvey]

On Wed, Oct 01, 2003 at 08:00:28PM -0700, Andrew Pinski wrote:
> >
> >        int i;
> >        (char)a = 5;

   I assumed it should be:

	(char)i = 5;

   I don't personally care. I've never used that extension. But I do not
understand the example.

Re: deriving template classes: gcc 3.4 complains

[Gabriel Dos Reis]

George Garvey <tmwg-gcc@inxservices.com> writes:

| On Wed, Oct 01, 2003 at 08:00:28PM -0700, Andrew Pinski wrote:
| > >
| > >        int i;
| > >        (char)a = 5;
| 
|    I assumed it should be:
| 
| 	(char)i = 5;

Indeed.

-- Gaby

Re: deriving template classes: gcc 3.4 complains

[Matt Austern]

On Oct 1, 2003, at 11:51 AM, Gerald Pfeifer wrote:

> On Wed, 1 Oct 2003, Joachim Schoeberl wrote:
>> test34.cpp: In constructor `derived<A>::derived(int)':
>> test34.cpp:14: error: `i' undeclared (first use this function)
>> test34.cpp:14: error: (Each undeclared identifier is reported only 
>> once
>> for each function it appears in.)
>>
>> Is there something wrong with my code ?
>
> I believe the third item under C++ at
>
>   http://gcc.gnu.org/gcc-3.4/changes.html
>
> might be relevant here.

For more information, possibly more than you want, see section 9.4.2, 
"Dependent Base Classes", of Vandevoorde and Josuttis's book _C++ 
Templates: The Complete Guide_.

This behavior is a fairly straightforward consequence of C++'s name 
lookup rules.  (Of course, I also have to admit that I didn't realize 
this was a consequence of those rules until I started using a compiler 
that actually enforced them.  I think HP's compiler may have been the 
first.)

			--Matt