A call to the function signal synchronizes with any resulting invocation of the signal handler so installed.
f is the function atomic_is_lock_free(), or
f is the member function is_lock_free(), or
f is a non-static member function invoked on an object A, such that A.is_lock_free() yields true, or
f is a non-member function, and for every pointer-to-atomic argument A passed to f, atomic_is_lock_free(A) yields true.
An evaluation is signal-safe unless it includes one of the following:
a call to any standard library function, except for plain lock-free atomic operations and functions explicitly identified as signal-safe. [ Note: This implicitly excludes the use of new and delete expressions that rely on a library-provided memory allocator. — end note ]
an access to an object with thread storage duration;
a dynamic_cast expression;
throwing of an exception;
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.
See also: ISO C 7.14