1520. INVOKE on member data pointer with too many arguments

Section: 22.10.4 [func.require] Status: C++11 Submitter: Howard Hinnant Opened: 2010-10-10 Last modified: 2016-01-28 10:19:27 UTC

Priority: Not Prioritized

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20.8.2 [func.require] p1 says:

1 Define INVOKE(f, t1, t2, ..., tN) as follows:

The question is: What happens in the 3rd and 4th bullets when N > 1?

Does the presence of t2, ..., tN get ignored, or does it make the INVOKE ill formed?

Here is sample code which presents the problem in a concrete example:

#include <functional>
#include <cassert>

struct S {
   char data;

typedef char S::*PMD;

int main()
   S s;
   PMD pmd = &S::data;
   std::reference_wrapper<PMD> r(pmd);
   r(s, 3.0) = 'a';  // well formed?
   assert(s.data == 'a');

Without the "3.0" the example is well formed.

[Note: Daniel provided wording to make it explicit that the above example is ill-formed. — end note ]

[ Post-Rapperswil ]

Moved to Tentatively Ready after 5 positive votes on c++std-lib.

[ Adopted at 2010-11 Batavia ]

Proposed resolution:

The wording refers to N3126.

Change 20.8.2 [func.require]/1 as indicated:

1 Define INVOKE(f, t1, t2, ..., tN) as follows: