m4: Debugging options

 
 2.5 Command line options for debugging
 ======================================
 
 Finally, there are several options for aiding in debugging 'm4' scripts.
 
 '-d[FLAGS]'
 '--debug[=FLAGS]'
      Set the debug-level according to the flags FLAGS.  The debug-level
      controls the format and amount of information presented by the
      debugging functions.  ⇒Debug Levels, for more details on the
      format and meaning of FLAGS.  If omitted, FLAGS defaults to 'aeq'.
 
 '--debugfile[=FILE]'
 '-o FILE'
 '--error-output=FILE'
      Redirect 'dumpdef' output, debug messages, and trace output to the
      named FILE.  Warnings, error messages, and 'errprint' output are
      still printed to standard error.  If these options are not used, or
      if FILE is unspecified (only possible for '--debugfile'), debug
      output goes to standard error; if FILE is the empty string, debug
      output is discarded.  ⇒Debug Output, for more details.  The
      option '--debugfile' may be given more than once, and order is
      significant with respect to file names.  The spellings '-o' and
      '--error-output' are misleading and inconsistent with other GNU
      tools; for now they are silently accepted as synonyms of
      '--debugfile' and only recognized once, but in a future version of
      M4, using them will cause a warning to be issued.
 
 '-l NUM'
 '--arglength=NUM'
      Restrict the size of the output generated by macro tracing to NUM
      characters per trace line.  If unspecified or zero, output is
      unlimited.  ⇒Debug Levels, for more details.
 
 '-t NAME'
 '--trace=NAME'
      This enables tracing for the macro NAME, at any point where it is
      defined.  NAME need not be defined when this option is given.  This
      option may be given more than once, and order is significant with
      respect to file names.  ⇒Trace, for more details.