module RbSys::Mkmf

def deffile_definition
  warn("EXPORT_PREFIX is not defined, please require \"mkmf\" before requiring \"rb_sys/mkmf\"") unless defined?(EXPORT_PREFIX)
  return unless defined?(EXPORT_PREFIX) && EXPORT_PREFIX
  @deffile_definition ||= <<~MAKE
    $(DEFFILE): $(TARGET_DIR)
    \t$(ECHO) generating $(@)
    \t$(Q) ($(COPY) $(srcdir)/$(TARGET).def $@ 2> /dev/null) || (echo EXPORTS && echo $(TARGET_ENTRY)) > $@
  MAKE
end