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David Carlton · Guest

Is code that does the following (in the order given) legal?

1) Define a templated class, but don't define all the methods in the
class.

2) Define an inlined function that uses one of the declared but not
defined methods in the class from step 1.

3) Define the method used in step 2.

4) Call the function from step 2.

I would assume not, but GCC 3.2, 3.3, and 3.4 all accept the example
code that I'll include after my signature. And I'm not good enough at
reading the standard to figure out whether the code is legal or not.

David Carlton
[email]carlton (AT) bactrian (DOT) org[/email]

#include <cstdio>

template< typename T >
class C {
public:
C( T data ) : data_( data ) {}

T data() const;

private:
T data_;
};

class D {
public:
int foo() { return C< int >( 17 ).data(); }
};

template< typename T >
T
C< T >::data() const {
return data_;
}

int
main() {
D d;

std::printf( "%dn", d.foo() );
}

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Francis Glassborow · Guest

In message <m3oerismap.fsf (AT) papaya (DOT) bactrian.org>, David Carlton
<carlton (AT) bactrian (DOT) org> writes

David Carlton · Guest

David Carlton <carlton (AT) bactrian (DOT) org> wrote

David Carlton · Guest

Here's another example involving methods of templated classes; I
guess I still don't understand the implications of what it means
for a member function of a templated class to be instantiated at
a given point in the code.

Question 1: Is this code legal? If it's not legal, is a compiler
allowed to accept it? (It compiles with GCC 3.2 and 3.4 but
not 3.3, for what that's worth.)

#include <cstdio>

template< typename T >
class D {
public:
D( T *data ) : data_( data ) {}
int foo();

private:
T *const data_;
};

template< typename T >
int D< T >::foo() {
return data_->foo();
}

class C;

class E {
public:
int foo( C *obj ) { return D< C >( obj ).foo(); }
};

class C {
public:
int foo() { return 123; }
};

int main() {
C c;
E e;

std::printf( "%dn", e.foo( &c ) );
}

Question 2: would it become legal if I were to move the definition
of D::foo() after the definition of C?

David Carlton
[email]carlton (AT) bactrian (DOT) org[/email]

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