/opt/IBM/openxlC/17.1.1/bin/ibm-clang -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations unistd/_PC_FALLOC.c -o unistd/_PC_FALLOC -D_POSIX_C_SOURCE=202405L -lm -lpthread -lrt -latomic
unistd/_PC_FALLOC.c:2:17: error: use of undeclared identifier '_PC_FALLOC'
int const foo = _PC_FALLOC;
                ^
1 error generated.