Section: 16.4.5.3 [reserved.names] Status: CD1 Submitter: Peter Dimov Opened: 2000-04-18 Last modified: 2016-01-28
Priority: Not Prioritized
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Discussion:
17.4.3.1/1 uses the term "depends" to limit the set of allowed specializations of standard templates to those that "depend on a user-defined name of external linkage."
This term, however, is not adequately defined, making it possible to construct a specialization that is, I believe, technically legal according to 17.4.3.1/1, but that specializes a standard template for a built-in type such as 'int'.
The following code demonstrates the problem:
#include <algorithm>template<class T> struct X { typedef T type; };namespace std { template<> void swap(::X<int>::type& i, ::X<int>::type& j); }
Proposed resolution:
Change "user-defined name" to "user-defined type".
Rationale:
This terminology is used in section 2.5.2 and 4.1.1 of The C++ Programming Language. It disallows the example in the issue, since the underlying type itself is not user-defined. The only possible problem I can see is for non-type templates, but there's no possible way for a user to come up with a specialization for bitset, for example, that might not have already been specialized by the implementor?
[Toronto: this may be related to issue 120.]
[post-Toronto: Judy provided the above proposed resolution and rationale.]