Fix signal handler

[elfring]

The function “fputs” does not belong to the list of async-signal-safe functions.
I guess that a different program design will be needed for your function “sig_handler”.

[p-gen]

Hi, the fputs are there to print fatal error messages and are almost immediately followed by an exit(EXIT_FAILURE); so I guess the risk is low.

I'll however add it to my TODO list. Thank you for your remark.

[elfring]

Would you like to consider other software design options?

• sigwaitinfo()
• Self-pipe trick
• Signal-safe locks