Asynchronous interrupts

If an asynchronous signal is being delivered to a thread running with POSIX(ON), the thread is interrupted for the signal only when the execution is:

In a user C or C++ routine
Just before a return to a C or C++ routine
Just before an invocation of a Language Environment library from a user routine

C or C++ routines might need to protect against asynchronous signals based on the application logic including the possible use of the POSIX signal-blocking function that is available.