cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration signal/sigwait.c -o signal/sigwait -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lintl -liconv
signal/sigwait.c: In function ‘main’:
signal/sigwait.c:16:23: error: implicit declaration of function ‘sigwait’ [-Wimplicit-function-declaration]
   16 |         if ( (errno = sigwait(&set, &signo)) < 0 )
      |                       ^~~~~~~