Delphi Cookbook - Third Edition

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A signal handler function must be very careful, since processing elsewhere may be interrupted at some arbitrary point in the execution of the program. POSIX has the concept of the safe function. If a signal interrupts the execution of an unsafe function, and the handler calls an unsafe function, then the behavior of the program is undefined.

– Linux man page

So, if you don't know which functions are safe to use inside a signal handler and which functions are not, refer to that list at: http://man7.org/linux/man-pages/man7/signal-safety.7.html and make sure you are not doing anything dangerous.

If you really want your signal handler to be safe and portable, consider not doing anything inside it except modifying a global interlocked ...