cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations signal/sigqueue.c -o signal/sigqueue -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
signal/sigqueue.c:5:40: error: use of undeclared identifier 'sigqueue'
    5 | int (*foo)(pid_t, int, union sigval) = sigqueue;
      |                                        ^
1 error generated.