17 Language support library [support]

17.13 Other runtime support [support.runtime]

17.13.5 Signal handlers [support.signal]

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

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

(2.1)
f is the function atomic_is_lock_free(), or
(2.2)
f is the member function is_lock_free(), or
(2.3)
f is a non-static member function of class atomic_flag, or
(2.4)
f is a non-member function, and the first parameter of f has type cv atomic_flag*, or
(2.5)
f is a non-static member function invoked on an object A, such that A.is_lock_free() yields true, or
(2.6)
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:

(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]
(3.2)
an access to an object with thread storage duration;
(3.3)
a dynamic_cast expression;
(3.4)
throwing of an exception;
(3.5)
control entering a try-block or function-try-block;
(3.6)
initialization of a variable with static storage duration requiring dynamic initialization ([basic.start.dynamic], [stmt.dcl])196 ; or
(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.

The function signal is signal-safe if it is invoked with the first argument equal to the signal number corresponding to the signal that caused the invocation of the handler.