cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration signal/sigqueue.c -o signal/sigqueue -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lintl -liconv
signal/sigqueue.c: In function ‘main’:
signal/sigqueue.c:37:14: error: implicit declaration of function ‘sigqueue’ [-Wimplicit-function-declaration]
   37 |         if ( sigqueue(getpid(), SIGUSR1, sv) < 0 )
      |              ^~~~~~~~