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