This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 108i. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2022-07-16


1249. Cv-qualification of nested lambda capture

Section: 7.5.5.3  [expr.prim.lambda.capture]     Status: DRWP     Submitter: James Widman     Date: 2011-03-02

[Accepted as a DR at the October, 2021 meeting.]

Consider the following example:

    void f(int i) {
      auto l1 = [i] {
        auto l2 = [&i] {
          ++i;    // Well-formed?
        };
      };
    }

Because the l1 lambda is not marked as mutable, its operator() is const; however, it is not clear from the wording of 7.5.5 [expr.prim.lambda] paragraph 16 whether the captured member of the enclosing lambda is considered const or not.

Proposed resolution (August, 2021):

Change 7.5.5.3 [expr.prim.lambda.capture] paragraph 14 as follows:

If a lambda-expression m2 captures an entity and that entity is captured by an immediately enclosing lambda-expression m1, then m2's capture is transformed as follows: