cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations signal/SIGEV_SIGNAL.c -o signal/SIGEV_SIGNAL -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
signal/SIGEV_SIGNAL.c:2:17: error: use of undeclared identifier 'SIGEV_SIGNAL'
int const foo = SIGEV_SIGNAL;
                ^
1 error generated.