cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration signal/str2sig.c -o signal/str2sig -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lcrypt -latomic
signal/str2sig.c: In function ‘main’:
signal/str2sig.c:10:14: error: implicit declaration of function ‘str2sig’ [-Werror=implicit-function-declaration]
   10 |         if ( str2sig("USR1", &signo) < 0 )
      |              ^~~~~~~
cc1: some warnings being treated as errors