This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

23. Some questions regarding partial ordering of function templates

Section: 13.7.7.3  [temp.func.order]     Status: NAD     Submitter: unknown     Date: unknown

Issue 1:

13.7.7.3 [temp.func.order] paragraph 2 says:

Given two overloaded function templates, whether one is more specialized than another can be determined by transforming each template in turn and using argument deduction (13.10.3 [temp.deduct] ) to compare it to the other.
13.10.3 [temp.deduct] now has 4 subsections describing argument deduction in different situations. I think this paragraph should point to a subsection of 13.10.3 [temp.deduct] .

Rationale:

This is not a defect; it is not necessary to pinpoint cross-references to this level of detail.

Issue 2:

13.7.7.3 [temp.func.order] paragraph 4 says:

Using the transformed function parameter list, perform argument deduction against the other function template. The transformed template is at least as specialized as the other if, and only if, the deduction succeeds and the deduced parameter types are an exact match (so the deduction does not rely on implicit conversions).
In "the deduced parameter types are an exact match", the terms exact match do not make it clear what happens when a type T is compared to the reference type T&. Is that an exact match?

Issue 3:

13.7.7.3 [temp.func.order] paragraph 5 says:

A template is more specialized than another if, and only if, it is at least as specialized as the other template and that template is not at least as specialized as the first.
What happens in this case: 
    template<class T> void f(T,int);
    template<class T> void f(T, T);
    void f(1,1);
For the first function template, there is no type deduction for the second parameter. So the rules in this clause seem to imply that the second function template will be chosen.

Rationale:

This is not a defect; the standard unambiguously makes the above example ill-formed due to ambiguity.

Additional note (April, 2011):

These points appear to have been addressed by previous resolutions, so presumably the issue is now NAD.

Rationale (August, 2011):

As given in the preceding note.