cc -pipe -O   -pthread  -Wall -Wextra -Werror=implicit-function-declaration signal/sigtimedwait.c -o signal/sigtimedwait -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread -lrt  -lrt -lcrypt
signal/sigtimedwait.c: In function 'main':
signal/sigtimedwait.c:32:7: error: implicit declaration of function 'sigqueue'; did you mean 'sigvec'? [-Werror=implicit-function-declaration]
  if ( sigqueue(getpid(), SIGUSR1, sv) < 0 )
       ^~~~~~~~
       sigvec
cc1: some warnings being treated as errors