This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 114a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-04-18

2572. Address of overloaded function with no target

Section: 12.3  [over.over]     Status: review     Submitter: Jason Merrill     Date: 2022-04-26

Consider:

  template <class T> T f(T);   // #1
  template <class T> T* f(T*); // #2
  auto p = &f<int>;

Accoring to 12.3 [over.over] paragraph 3 and 12.3 [over.over] paragraph 5:

The specialization, if any, generated by template argument deduction (13.10.4 [temp.over], 13.10.3.3 [temp.deduct.funcaddr], 13.10.2 [temp.arg.explicit]) for each function template named is added to the set of selected functions considered.

[...]

Any given function template specialization F1 is eliminated if the set contains a second function template specialization whose function template is more specialized than the function template of F1 according to the partial ordering rules of 13.7.7.3 [temp.func.order]. After such eliminations, if any, there shall remain exactly one selected function.

Major implementations reject the example as ambiguous, yet the wording specifies to unambiguously choose #2.

Suggested resolution [SUPERSEDED]:

Change in 12.3 [over.over] paragraph 5 as follows:

Any given function template specialization F1 is eliminated if the set contains a second function template specialization whose function template is more specialized better than the function template of F1. If there is no target, a function template is better than another if it is more constrained than the other; otherwise a function template is better than another if it is more specialized than the other according to the partial ordering rules of 13.7.7.3 [temp.func.order]. After such eliminations, if any, there shall remain exactly one selected function.

Proposed resolution:

Change in 12.3 [over.over] paragraph 5 as follows:

Any If there is a target, any given function template specialization F1 is eliminated if the set contains a second function template specialization whose function template is more specialized than the function template of F1 according to the partial ordering rules of 13.7.7.3 [temp.func.order]. After such eliminations, if any, there shall remain exactly one selected function.