cc -O2 -pipe  -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 
signal/sigqueue.c:37:7: error: call to undeclared function 'sigqueue'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
        if ( sigqueue(getpid(), SIGUSR1, sv) < 0 )
             ^
1 error generated.