Re: problem with default argument with template args

From:

red floyd <redfloyd@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 18 Nov 2009 12:46:37 CST

Message-ID:

<d2d42b94-8027-40fb-8df9-9cff0791b531@k9g2000vbl.googlegroups.com>

On Nov 17, 6:13 pm, Andrew <marlow.and...@googlemail.com> wrote:

On 17 Nov, 21:02, Neil Butterworth <nbutterworth1...@gmail.com> wrote:

Andrew wrote:

I cannot see what is wrong with the code below:

template<class A, class B>
class Arg {
public:
     Arg() {};
};

template<class A, class B>
class User {
public:
     User(const char* username,
          Arg<A,B> arg = Arg<A,B>(),
          bool flag = false)
     {
     };
};

gcc fails to compile it. The error output is:

ex2.cpp:12: error: expected `,' or `...' before '>' token
ex2.cpp:12: error: missing `>' to terminate the template argument list
ex2.cpp:12: error: wrong number of template arguments (1, should be 2)
ex2.cpp:3: error: provided for `template<class A, class B> class Arg'

Taking out the defaulting of the template argument makes the problem
go away.

It compiles for me with g++ 4.4.0 - which version of g++ are you using?

3.4.4-3. I realise this is quite old. It is where gcc is in cygwin at
the moment. AFAIK the only way to get a more recent one is to build it
from the source. I might just do that.

So it looks like the code is legal than. Good. I must admit, I
couldn't see what was wrong with it.

4.1.0 (at least shipped with SLES 10 also has the bug.

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