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.