/opt/IBM/openxlC/17.1.1/bin/ibm-clang -pthread  -Wall -Wextra -Werror=implicit-function-declaration pthread/pthread_cond_clockwait.c -o pthread/pthread_cond_clockwait -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -latomic
pthread/pthread_cond_clockwait.c:20:16: error: call to undeclared function 'pthread_cond_clockwait'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
        if ( (errno = pthread_cond_clockwait(&cnd, &mtx, CLOCK_MONOTONIC,
                      ^
1 error generated.