[ Kona 2022-11-10; SG1 yields a recommendation ]

Poll: Adopt the proposed resolution for LWG3756
"f is a non-static member function invoked on an atomic_flag object, or"
"f is a non-member function, and every pointer-to- atomic argument passed to f is atomic_flag, or"

SF F N A SA
11 3 0 0 0

Unanimous consent

Previous resolution [SUPERSEDED]:

This wording is relative to N4917.

1. Modify [support.signal] as indicated:

   -1- A call to the function signal synchronizes with any resulting invocation of the signal handler so installed.

   -2- A plain lock-free atomic operation is an invocation of a function f from [atomics], such that:

   1. (2.1) — f is the function atomic_is_lock_free(), or
   2. (2.2) — f is the member function is_lock_free(), or
   3. (2.?) — f is a non-static member function invoked on an atomic_flag object, or
   4. (2.?) — f is a non-member function, and every pointer-to-atomic argument passed to f is atomic_flag, or
   5. (2.3) — f is a non-static member function invoked on an object A, such that A.is_lock_free() yields true, or
   6. (2.4) — f is a non-member function, and for every pointer-to-atomic argument A passed to f, atomic_is_lock_free(A) yields true.

   -3- An evaluation is signal-safe unless it includes one of the following:

   1. (3.1) — a call to any standard library function, except for plain lock-free atomic operations and functions explicitly identified as signal-safe;

      [Note 1: This implicitly excludes the use of new and delete expressions that rely on a library-provided memory allocator. — end note]

   2. (3.2) — an access to an object with thread storage duration;
   3. (3.3) — a dynamic_cast expression;
   4. (3.4) — throwing of an exception;
   5. (3.5) — control entering a try-block or function-try-block;
   6. (3.6) — initialization of a variable with static storage duration requiring dynamic initialization ([basic.start.dynamic], [stmt.dcl])²⁰⁶; or
   7. (3.7) — waiting for the completion of the initialization of a variable with static storage duration ([stmt.dcl]).

   A signal handler invocation has undefined behavior if it includes an evaluation that is not signal-safe.