/opt/IBM/openxlC/17.1.1/bin/ibm-clang -pthread   -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations mqueue/O_EXCL.c -o mqueue/O_EXCL -D_POSIX_C_SOURCE=202405L -lm -lpthread -lrt  -liconv -latomic
mqueue/O_EXCL.c:4:2: error: "O_EXCL is not defined"
#error "O_EXCL is not defined"
 ^
1 error generated.