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Hi,
I have the following code which compiles and runs fine on GCC 4.3.2:

//--------------------------------------------------------
struct A {virtual int getnum()=0;};

A* func(int numin) {
static int num;
num=numin;
struct B : public A {
int getnum(){
delete this;
return num;
}
};
return new B();
}

int main() {
func(3)->getnum();
return 0;
}
//--------------------------------------------------------

But when I do the same thing with a templated type instead of 'int',
the code compiles but I get a link error:

//--------------------------------------------------------
template<typename T>
struct A {virtual T getnum()=0;};

template<typename T>
A<T>* func(T numin) {
static T num;
num=numin;
struct B : public A<T> {
T getnum(){
delete this;
return num; // <----- link error: undefined reference
to 'num'
}
};
return new B();
}

int main() {
func(3)->getnum();
return 0;
}
//--------------------------------------------------------

Is this a compiler bug, or is this actually not supposed to work with
templates?

wrote:
> Hi,
> I have the following code which compiles and runs fine on GCC 4.3.2:
>
[snip]
>
> But when I do the same thing with a templated type instead of 'int',
> the code compiles but I get a link error:
>
> //--------------------------------------------------------
> template<typename T>
> struct A {virtual T getnum()=0;};
>
> template<typename T>
> A<T>* func(T numin) {
> static T num;
> num=numin;
> struct B : public A<T> {
> T getnum(){
> delete this;
> return num; // <----- link error: undefined reference
> to 'num'
> }
> };
> return new B();
> }
>
> int main() {
> func(3)->getnum();
> return 0;
> }
> //--------------------------------------------------------
>
> Is this a compiler bug, or is this actually not supposed to work with
> templates?

This is a compiler bug. AFAIK the program is well formed Comeau compiles
it without problem.

--
Michael

On Feb 3, 2:36 pm, Michael DOUBEZ <michael.dou...@free.fr> wrote:
> ym...@hotmail.com wrote:

> > I have the following code which compiles and runs fine on
> > GCC 4.3.2:

> [snip]

> > But when I do the same thing with a templated type instead
> > of 'int', the code compiles but I get a link error:

> > //--------------------------------------------------------
> > template<typename T>
> > struct A {virtual T getnum()=0;};

> > template<typename T>
> > A<T>* func(T numin) {
> > static T num;
> > num=numin;
> > struct B : public A<T> {
> > T getnum(){
> > delete this;
> > return num; // <----- link error: undefined reference
> > to 'num'
> > }
> > };
> > return new B();
> > }

> > int main() {
> > func(3)->getnum();
> > return 0;
> > }
> > //--------------------------------------------------------

> > Is this a compiler bug, or is this actually not supposed to
> > work with templates?

> This is a compiler bug. AFAIK the program is well formed
> Comeau compiles it without problem.

Does it link as well? His problem only occured when linking.

According to the standard (at least as far as I can tell), it's
legal, and any conforming compiler should be able to handle it.
The basic rule (in §9. says that "Declarations in a local
class can use only type names, static variables, extern
variables and functions, and enumerators from the enclosing
scope", and I can't find anything which would change this in a
template. (There are a few special rules for locally declared
names in templates, but either they apply only to class
templates, or they only concern the template parameters
themselves.)

--
James Kanze (GABI Software) email:
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