Templates & Typdefs with g++ v4.0.0

[Pete]

In moving from gcc 3.4 to v4.0.0 my code stops working (what a
surprise).

Basically, I have a header file:
____________________
template<int I, int J>
class Inner
{
Inner(){};
};

class Outer
{
Outer(){};
typedef Inner<1,2> Foo;
};
---------------
and a source file:
___________________
#include "test.h"
int main(void)
{
};
template class Outer::Foo;
-------------------
which, when compiling, gives the errors

test.cpp:5: error: using typedef-name 'Outer::Foo' after 'class'
test.h:10: error: 'Outer::Foo' has a previous declaration here

VS.NET gives the error "C2242: typedef name cannot follow
class/struct/union"

I'm a bit stumped, and I don't know templates very well. The source
file code had originally read:

.....
template Outer::Foo;

which compiles under VS.NET, but gives the G++ error:

test.cpp:8: error: expected unqualified-id before ';' token

Unfortunately I am in the position that I need it to compile under both
OSs.

[Gernot Frisch]

"Pete" <si***@hotmail.com> schrieb im Newsbeitrag
news:11*********************@g49g2000cwa.googlegro ups.com...

In moving from gcc 3.4 to v4.0.0 my code stops working (what a
surprise).

Basically, I have a header file:
____________________
template<int I, int J>
class Inner
{
Inner(){};
};

class Outer
{
Outer(){};
typedef Inner<1,2> Foo;
};
---------------
and a source file:
___________________
#include "test.h"
int main(void)
{
};
template class Outer::Foo;

you don't refer to this line at all, why don't you just dump it? The
declaration of the "Outer" class including the "foo" _is_ done in the
header file.

[Pete]

In simplifying the problem, I may have oversimplified the (100K lines
of code) file structure to reproduce the error messages :-)

If the offending line is commented out I get a whole mass of nasties
popping up in other places (in g++, but not VS.NET!).

Just noticed that my start version of gcc was 3.2.2, not 3.4

[Gernot Frisch]

"Pete" <si***@hotmail.com> schrieb im Newsbeitrag
news:11*********************@o13g2000cwo.googlegro ups.com...

In simplifying the problem, I may have oversimplified the (100K
lines
of code) file structure to reproduce the error messages :-)

If the offending line is commented out I get a whole mass of nasties
popping up in other places (in g++, but not VS.NET!).

Just noticed that my start version of gcc was 3.2.2, not 3.4

So.. post these instead. Because what you do in the header is
sufficient for declaration.
-Gernot

[Rob Williscroft]

Gernot Frisch wrote in news:3i************@individual.net in
comp.lang.c++:

"Pete" <si***@hotmail.com> schrieb im Newsbeitrag
news:11*********************@o13g2000cwo.googlegro ups.com...

In simplifying the problem, I may have oversimplified the (100K
lines
of code) file structure to reproduce the error messages :-)

If the offending line is commented out I get a whole mass of nasties
popping up in other places (in g++, but not VS.NET!).

Just noticed that my start version of gcc was 3.2.2, not 3.4

So.. post these instead. Because what you do in the header is
sufficient for declaration.

Declaration isn't the point, the line:

template class Outer::Foo;

Is an attempt to explicitly instantiate the class Inner<1, 2>.

Writeing:

template class Inner< 1, 2 >;

should satisfy both g++ and MSVC.

From a brief reading of 14.7.2 Explicit instantiation, it seems that
the Standard doesn't require the use of 'class', but it does require
that the /declaraion/ following 'template' be either a /template-id/
or a /template-name/ a typedef is *never* one of those, so the only
portable solution is to use the replacment above.

Rob.
--
http://www.victim-prime.dsl.pipex.com/