cc -pipe -O   -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  -lrt -lcrypt
signal/str2sig.c: In function 'main':
signal/str2sig.c:10:7: error: implicit declaration of function 'str2sig'; did you mean 'strstr'? [-Werror=implicit-function-declaration]
  if ( str2sig("USR1", &signo) < 0 )
       ^~~~~~~
       strstr
cc1: some warnings being treated as errors