Re: References to references
on Tue Dec 27 2011, Kelvin Chung <kelvSYC-AT-mac.com> wrote:
I'm getting an unforseen problem when I'm trying to compile code for
older compilers. The following code compiles in clang 3.0 on a Mac:
template <class Key>
struct Foo {
typedef Key& key_type;
virtual Bar mapKey(const key_type& key) = 0;
};
However, when I compile with gcc 4.1.2 on SUSE Linux, I get "cannot declare reference to 'Key&', specifically wrt to mapKey().
I'm trying to find the root cause of this: Is it a C++11-specifc
thing,
Yes, reference-collapsing is a new feature in C++11.
and thus barfing on gcc 4.1.2, which IIRC has no C++11 support? Is it
simply that I am expecting that "const key_type&" resolves to "Key&"
(ie. the references "collapse"), when it shouldn't? What should be
the workaround for getting this snippet to compile under gcc 4.1.2?
virtual Bar mapKey(
const
typename remove_reference<key_type>::type // <== here
& key
) = 0;
You can find remove_reference in Boost if it's not in gcc 4.1.2 in
namespace std::tr1 (I don't remember if they supply it in that version).
--
Dave Abrahams
BoostPro Computing
http://www.boostpro.com
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