Proposed resolution (approved by CWG 2026-10-06):

Change in 9.4.1 [dcl.contract.func] paragraph 9 as follows:

The function contract assertions of a function are considered to be needed (13.9.2 [temp.inst]) when

• the function is odr-used (6.3 [basic.def.odr]) or ,
• the function is declared as a virtual function (11.7.4 [class.abstract]), or
• the function is defined.

(From submission #1003.)

With P3097R3 (Contracts for C++: Virtual functions), adopted in June, 2026, function contract assertions are now required to be instantiated in cases where a pure virtual function is called, even when the function is not odr-used.