7.6.1.3 Symbols

• -D
  • -D name

    Predefine name as a macro, with definition 1.

    E.g.,

  • -D name=value

    Predefine name as a macro, with definition value. The contents of the definition are tokenized and processed as if they appeared during translation phase three in a #define directive. In particular, the definition will be truncated by embedded newline characters.

• -U

  Cancel any previous name definition, either built-in or provided with a -D option.

-D and -U options are processed in the given order on the command-line. All -imacros file and -include file options are processed after all -D and -U options.