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 -lintl -liconv relibc getrlimit(3, 0x7ffffffffc80): not implemented relibc getrlimit(3, 0x7ffffffffba0): not implemented relibc getrlimit(9, 0x7ffffffffb60): not implemented relibc getrlimit(9, 0x7ffffffffb90): not implemented relibc getrlimit(5, 0x7ffffffffb90): not implemented relibc getrlimit(9, 0x7ffffffffb60): not implemented 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