Are there situations where signal processing is impossible or unacceptable?

Yes, there are situations where signal handling is impossible or inadvisable:

• Signals that cannot be ignored or blocked. For example, SIGKILL and SIGSTOP in Unix systems cannot be caught or handled by a program.

• Critical signals requiring immediate termination. If a program receives a signal indicating a serious error (e.g., SIGSEGV — segmentation fault), handling may be impossible or dangerous.

• Time constraints. If a signal arrives too frequently or at an inappropriate moment (e.g., during a critical section), handling it may lead to race conditions or incorrect operation.

• Security and policy. In some systems, handling certain signals may be prohibited for security reasons.

Therefore, it is important to understand the nature of the signal and the context in which it arrives to decide correctly whether to handle it or not.