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