-CFLAGS += -Wc,"langlvl(extended),spill(2000)" -Wc,"ros" $(ICU_BUILD_OPTIONS) $(ICU_IEEE) -Wc,dll,expo
-CXXFLAGS += -Wc,"langlvl(extended),spill(2000)" -Wc,"ros" $(ICU_BUILD_OPTIONS) $(ICU_IEEE) -Wc,dll,expo
-DEFS += -D_OPEN_THREADS -D_XOPEN_SOURCE_EXTENDED -D_MSE_PROTOS -D_SHR_TZNAME -D_SHR_TIMEZONE -DU_LIBICUDATA_NAME=\"$(ICUPREFIX)$(DATA_STUBNAME)$(ICULIBSUFFIX)\"
+# The RENT option makes the program reentrant. This may not really have the same
+# meaning as normal reentrancy on other platforms. See the z/OS documentation
+# for details. This is the default for C++, but not C.
+# The DLL option must be used by the callee and caller code when using shared libraries.
+# NOCSECT might be used as an optimization option.
+# -+ means accept any file extension as a C++ file. By default only .C is accepted.
+CFLAGS += -Wc,DLL,ROS,RENT,'ARCH(7)','LOC(POSIX)',NOANSIALIAS,'LANGLVL(EXTENDED)' $(ICU_IEEE)
+CXXFLAGS += -Wc,DLL,ROS,RTTI,'ARCH(7)','LOC(POSIX)',NOANSIALIAS,'LANGLVL(EXTENDED0X)' $(ICU_IEEE) -+