Re: [Boost-users] [mpl] Is it possible to mpl_assert dependingonthe derivation of a class

-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Martin Apel Sent: 21 August 2007 15:00 To: boost-users@lists.boost.org Subject: Re: [Boost-users] [mpl] Is it possible to mpl_assert dependingonthe derivation of a class

Hughes, James wrote:

...

Just a quick addendum to this. I tried out a combination of the two - using a BOOST_STATIC_ASSERT((boost::is_base_of >::value)) inside the do_it function described above, and found what I thought was odd behaviour with is_base_of.

The following excerpt shows the behaviour

class A {};

class B : public A {};

typedef A C;

BOOST_STATIC_ASSERT((boost::is_base_of >::value))

// this

...

passes

BOOST_STATIC_ASSERT((boost::is_base_of >::value))

// this

...

fails

I would expect both to pass, as is_base_of should

return true when

...

both parameters are the same, and I thought that

typedef did make

...

classes the same/equivalent

http://www.boost.org/doc/html/boost_typetraits/reference.html#boost_ty

...

petraits.is_base_of

Is there something I am missing about typedef? Or is boost::is_base_of unable to handles the aliasing?

James

Hi James,

I tried this with GCC 4.2 and 3.4.6 under Linux. It passes for both cases. So it might be your compiler, which is doing something wrong.

Martin

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I'm using gcc 3.4.3 (Cross compiler to Arm). I had a thought it might be down to having some pure virtual functions in A, which meant that my typedef resulting in an incomplete type, but I removed those as a test and still got the same error. But that wouldn't explain why changing from a typedef to a derivation fixed the problem. Using boost 1.33.1 btw. I'll assume it's the compiler for now!! James This message (including any attachments) contains confidential and/or proprietary information intended only for the addressee. Any unauthorized disclosure, copying, distribution or reliance on the contents of this information is strictly prohibited and may constitute a violation of law. If you are not the intended recipient, please notify the sender immediately by responding to this e-mail, and delete the message from your system. If you have any questions about this e-mail please notify the sender immediately.